aboutsummaryrefslogtreecommitdiff
path: root/absl/synchronization/mutex.cc
diff options
context:
space:
mode:
authorBenjamin Barenblat <bbaren@google.com>2023-09-07 13:16:09 -0400
committerBenjamin Barenblat <bbaren@google.com>2023-09-07 13:16:09 -0400
commit6fdbff8bbce2a1debdc060df381f39e3dcfb65af (patch)
tree71f1ef38477a65d5cce472fc042c90087c2bb351 /absl/synchronization/mutex.cc
parent8d4a80fe37176b1170d7dce0772dea9584ec3e32 (diff)
parent29bf8085f3bf17b84d30e34b3d7ff8248fda404e (diff)
downloadabseil-6fdbff8bbce2a1debdc060df381f39e3dcfb65af.tar.gz
abseil-6fdbff8bbce2a1debdc060df381f39e3dcfb65af.tar.bz2
abseil-6fdbff8bbce2a1debdc060df381f39e3dcfb65af.zip
Merge new upstream LTS 20230802.0
Diffstat (limited to 'absl/synchronization/mutex.cc')
-rw-r--r--absl/synchronization/mutex.cc818
1 files changed, 407 insertions, 411 deletions
diff --git a/absl/synchronization/mutex.cc b/absl/synchronization/mutex.cc
index 064ccb74..3aa5560a 100644
--- a/absl/synchronization/mutex.cc
+++ b/absl/synchronization/mutex.cc
@@ -35,10 +35,9 @@
#include <algorithm>
#include <atomic>
-#include <cinttypes>
#include <cstddef>
+#include <cstdlib>
#include <cstring>
-#include <iterator>
#include <thread> // NOLINT(build/c++11)
#include "absl/base/attributes.h"
@@ -55,7 +54,6 @@
#include "absl/base/internal/thread_identity.h"
#include "absl/base/internal/tsan_mutex_interface.h"
#include "absl/base/optimization.h"
-#include "absl/base/port.h"
#include "absl/debugging/stacktrace.h"
#include "absl/debugging/symbolize.h"
#include "absl/synchronization/internal/graphcycles.h"
@@ -63,6 +61,7 @@
#include "absl/time/time.h"
using absl::base_internal::CurrentThreadIdentityIfPresent;
+using absl::base_internal::CycleClock;
using absl::base_internal::PerThreadSynch;
using absl::base_internal::SchedulingGuard;
using absl::base_internal::ThreadIdentity;
@@ -98,18 +97,15 @@ ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES
absl::base_internal::AtomicHook<void (*)(int64_t wait_cycles)>
submit_profile_data;
ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES absl::base_internal::AtomicHook<void (*)(
- const char *msg, const void *obj, int64_t wait_cycles)>
+ const char* msg, const void* obj, int64_t wait_cycles)>
mutex_tracer;
ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES
- absl::base_internal::AtomicHook<void (*)(const char *msg, const void *cv)>
- cond_var_tracer;
-ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES absl::base_internal::AtomicHook<
- bool (*)(const void *pc, char *out, int out_size)>
- symbolizer(absl::Symbolize);
+absl::base_internal::AtomicHook<void (*)(const char* msg, const void* cv)>
+ cond_var_tracer;
} // namespace
-static inline bool EvalConditionAnnotated(const Condition *cond, Mutex *mu,
+static inline bool EvalConditionAnnotated(const Condition* cond, Mutex* mu,
bool locking, bool trylock,
bool read_lock);
@@ -117,19 +113,15 @@ void RegisterMutexProfiler(void (*fn)(int64_t wait_cycles)) {
submit_profile_data.Store(fn);
}
-void RegisterMutexTracer(void (*fn)(const char *msg, const void *obj,
+void RegisterMutexTracer(void (*fn)(const char* msg, const void* obj,
int64_t wait_cycles)) {
mutex_tracer.Store(fn);
}
-void RegisterCondVarTracer(void (*fn)(const char *msg, const void *cv)) {
+void RegisterCondVarTracer(void (*fn)(const char* msg, const void* cv)) {
cond_var_tracer.Store(fn);
}
-void RegisterSymbolizer(bool (*fn)(const void *pc, char *out, int out_size)) {
- symbolizer.Store(fn);
-}
-
namespace {
// Represents the strategy for spin and yield.
// See the comment in GetMutexGlobals() for more information.
@@ -148,25 +140,24 @@ absl::Duration MeasureTimeToYield() {
return absl::Now() - before;
}
-const MutexGlobals &GetMutexGlobals() {
+const MutexGlobals& GetMutexGlobals() {
ABSL_CONST_INIT static MutexGlobals data;
absl::base_internal::LowLevelCallOnce(&data.once, [&]() {
- const int num_cpus = absl::base_internal::NumCPUs();
- data.spinloop_iterations = num_cpus > 1 ? 1500 : 0;
- // If this a uniprocessor, only yield/sleep.
- // Real-time threads are often unable to yield, so the sleep time needs
- // to be long enough to keep the calling thread asleep until scheduling
- // happens.
- // If this is multiprocessor, allow spinning. If the mode is
- // aggressive then spin many times before yielding. If the mode is
- // gentle then spin only a few times before yielding. Aggressive spinning
- // is used to ensure that an Unlock() call, which must get the spin lock
- // for any thread to make progress gets it without undue delay.
- if (num_cpus > 1) {
+ if (absl::base_internal::NumCPUs() > 1) {
+ // If this is multiprocessor, allow spinning. If the mode is
+ // aggressive then spin many times before yielding. If the mode is
+ // gentle then spin only a few times before yielding. Aggressive spinning
+ // is used to ensure that an Unlock() call, which must get the spin lock
+ // for any thread to make progress gets it without undue delay.
+ data.spinloop_iterations = 1500;
data.mutex_sleep_spins[AGGRESSIVE] = 5000;
data.mutex_sleep_spins[GENTLE] = 250;
data.mutex_sleep_time = absl::Microseconds(10);
} else {
+ // If this a uniprocessor, only yield/sleep. Real-time threads are often
+ // unable to yield, so the sleep time needs to be long enough to keep
+ // the calling thread asleep until scheduling happens.
+ data.spinloop_iterations = 0;
data.mutex_sleep_spins[AGGRESSIVE] = 0;
data.mutex_sleep_spins[GENTLE] = 0;
data.mutex_sleep_time = MeasureTimeToYield() * 5;
@@ -219,8 +210,7 @@ static void AtomicSetBits(std::atomic<intptr_t>* pv, intptr_t bits,
v = pv->load(std::memory_order_relaxed);
} while ((v & bits) != bits &&
((v & wait_until_clear) != 0 ||
- !pv->compare_exchange_weak(v, v | bits,
- std::memory_order_release,
+ !pv->compare_exchange_weak(v, v | bits, std::memory_order_release,
std::memory_order_relaxed)));
}
@@ -235,8 +225,7 @@ static void AtomicClearBits(std::atomic<intptr_t>* pv, intptr_t bits,
v = pv->load(std::memory_order_relaxed);
} while ((v & bits) != 0 &&
((v & wait_until_clear) != 0 ||
- !pv->compare_exchange_weak(v, v & ~bits,
- std::memory_order_release,
+ !pv->compare_exchange_weak(v, v & ~bits, std::memory_order_release,
std::memory_order_relaxed)));
}
@@ -247,7 +236,7 @@ ABSL_CONST_INIT static absl::base_internal::SpinLock deadlock_graph_mu(
absl::kConstInit, base_internal::SCHEDULE_KERNEL_ONLY);
// Graph used to detect deadlocks.
-ABSL_CONST_INIT static GraphCycles *deadlock_graph
+ABSL_CONST_INIT static GraphCycles* deadlock_graph
ABSL_GUARDED_BY(deadlock_graph_mu) ABSL_PT_GUARDED_BY(deadlock_graph_mu);
//------------------------------------------------------------------
@@ -291,7 +280,7 @@ enum { // Event flags
// Properties of the events.
static const struct {
int flags;
- const char *msg;
+ const char* msg;
} event_properties[] = {
{SYNCH_F_LCK_W | SYNCH_F_TRY, "TryLock succeeded "},
{0, "TryLock failed "},
@@ -316,12 +305,12 @@ ABSL_CONST_INIT static absl::base_internal::SpinLock synch_event_mu(
// Can't be too small, as it's used for deadlock detection information.
static constexpr uint32_t kNSynchEvent = 1031;
-static struct SynchEvent { // this is a trivial hash table for the events
+static struct SynchEvent { // this is a trivial hash table for the events
// struct is freed when refcount reaches 0
int refcount ABSL_GUARDED_BY(synch_event_mu);
// buckets have linear, 0-terminated chains
- SynchEvent *next ABSL_GUARDED_BY(synch_event_mu);
+ SynchEvent* next ABSL_GUARDED_BY(synch_event_mu);
// Constant after initialization
uintptr_t masked_addr; // object at this address is called "name"
@@ -329,13 +318,13 @@ static struct SynchEvent { // this is a trivial hash table for the events
// No explicit synchronization used. Instead we assume that the
// client who enables/disables invariants/logging on a Mutex does so
// while the Mutex is not being concurrently accessed by others.
- void (*invariant)(void *arg); // called on each event
- void *arg; // first arg to (*invariant)()
- bool log; // logging turned on
+ void (*invariant)(void* arg); // called on each event
+ void* arg; // first arg to (*invariant)()
+ bool log; // logging turned on
// Constant after initialization
- char name[1]; // actually longer---NUL-terminated string
-} * synch_event[kNSynchEvent] ABSL_GUARDED_BY(synch_event_mu);
+ char name[1]; // actually longer---NUL-terminated string
+}* synch_event[kNSynchEvent] ABSL_GUARDED_BY(synch_event_mu);
// Ensure that the object at "addr" has a SynchEvent struct associated with it,
// set "bits" in the word there (waiting until lockbit is clear before doing
@@ -344,11 +333,11 @@ static struct SynchEvent { // this is a trivial hash table for the events
// the string name is copied into it.
// When used with a mutex, the caller should also ensure that kMuEvent
// is set in the mutex word, and similarly for condition variables and kCVEvent.
-static SynchEvent *EnsureSynchEvent(std::atomic<intptr_t> *addr,
- const char *name, intptr_t bits,
+static SynchEvent* EnsureSynchEvent(std::atomic<intptr_t>* addr,
+ const char* name, intptr_t bits,
intptr_t lockbit) {
uint32_t h = reinterpret_cast<uintptr_t>(addr) % kNSynchEvent;
- SynchEvent *e;
+ SynchEvent* e;
// first look for existing SynchEvent struct..
synch_event_mu.Lock();
for (e = synch_event[h];
@@ -360,9 +349,9 @@ static SynchEvent *EnsureSynchEvent(std::atomic<intptr_t> *addr,
name = "";
}
size_t l = strlen(name);
- e = reinterpret_cast<SynchEvent *>(
+ e = reinterpret_cast<SynchEvent*>(
base_internal::LowLevelAlloc::Alloc(sizeof(*e) + l));
- e->refcount = 2; // one for return value, one for linked list
+ e->refcount = 2; // one for return value, one for linked list
e->masked_addr = base_internal::HidePtr(addr);
e->invariant = nullptr;
e->arg = nullptr;
@@ -372,19 +361,19 @@ static SynchEvent *EnsureSynchEvent(std::atomic<intptr_t> *addr,
AtomicSetBits(addr, bits, lockbit);
synch_event[h] = e;
} else {
- e->refcount++; // for return value
+ e->refcount++; // for return value
}
synch_event_mu.Unlock();
return e;
}
// Deallocate the SynchEvent *e, whose refcount has fallen to zero.
-static void DeleteSynchEvent(SynchEvent *e) {
+static void DeleteSynchEvent(SynchEvent* e) {
base_internal::LowLevelAlloc::Free(e);
}
// Decrement the reference count of *e, or do nothing if e==null.
-static void UnrefSynchEvent(SynchEvent *e) {
+static void UnrefSynchEvent(SynchEvent* e) {
if (e != nullptr) {
synch_event_mu.Lock();
bool del = (--(e->refcount) == 0);
@@ -398,11 +387,11 @@ static void UnrefSynchEvent(SynchEvent *e) {
// Forget the mapping from the object (Mutex or CondVar) at address addr
// to SynchEvent object, and clear "bits" in its word (waiting until lockbit
// is clear before doing so).
-static void ForgetSynchEvent(std::atomic<intptr_t> *addr, intptr_t bits,
+static void ForgetSynchEvent(std::atomic<intptr_t>* addr, intptr_t bits,
intptr_t lockbit) {
uint32_t h = reinterpret_cast<uintptr_t>(addr) % kNSynchEvent;
- SynchEvent **pe;
- SynchEvent *e;
+ SynchEvent** pe;
+ SynchEvent* e;
synch_event_mu.Lock();
for (pe = &synch_event[h];
(e = *pe) != nullptr && e->masked_addr != base_internal::HidePtr(addr);
@@ -423,9 +412,9 @@ static void ForgetSynchEvent(std::atomic<intptr_t> *addr, intptr_t bits,
// Return a refcounted reference to the SynchEvent of the object at address
// "addr", if any. The pointer returned is valid until the UnrefSynchEvent() is
// called.
-static SynchEvent *GetSynchEvent(const void *addr) {
+static SynchEvent* GetSynchEvent(const void* addr) {
uint32_t h = reinterpret_cast<uintptr_t>(addr) % kNSynchEvent;
- SynchEvent *e;
+ SynchEvent* e;
synch_event_mu.Lock();
for (e = synch_event[h];
e != nullptr && e->masked_addr != base_internal::HidePtr(addr);
@@ -440,17 +429,17 @@ static SynchEvent *GetSynchEvent(const void *addr) {
// Called when an event "ev" occurs on a Mutex of CondVar "obj"
// if event recording is on
-static void PostSynchEvent(void *obj, int ev) {
- SynchEvent *e = GetSynchEvent(obj);
+static void PostSynchEvent(void* obj, int ev) {
+ SynchEvent* e = GetSynchEvent(obj);
// logging is on if event recording is on and either there's no event struct,
// or it explicitly says to log
if (e == nullptr || e->log) {
- void *pcs[40];
+ void* pcs[40];
int n = absl::GetStackTrace(pcs, ABSL_ARRAYSIZE(pcs), 1);
// A buffer with enough space for the ASCII for all the PCs, even on a
// 64-bit machine.
char buffer[ABSL_ARRAYSIZE(pcs) * 24];
- int pos = snprintf(buffer, sizeof (buffer), " @");
+ int pos = snprintf(buffer, sizeof(buffer), " @");
for (int i = 0; i != n; i++) {
int b = snprintf(&buffer[pos], sizeof(buffer) - static_cast<size_t>(pos),
" %p", pcs[i]);
@@ -472,13 +461,13 @@ static void PostSynchEvent(void *obj, int ev) {
// get false positive race reports later.
// Reuse EvalConditionAnnotated to properly call into user code.
struct local {
- static bool pred(SynchEvent *ev) {
+ static bool pred(SynchEvent* ev) {
(*ev->invariant)(ev->arg);
return false;
}
};
Condition cond(&local::pred, e);
- Mutex *mu = static_cast<Mutex *>(obj);
+ Mutex* mu = static_cast<Mutex*>(obj);
const bool locking = (flags & SYNCH_F_UNLOCK) == 0;
const bool trylock = (flags & SYNCH_F_TRY) != 0;
const bool read_lock = (flags & SYNCH_F_R) != 0;
@@ -504,32 +493,32 @@ static void PostSynchEvent(void *obj, int ev) {
// PerThreadSynch struct points at the most recent SynchWaitParams struct when
// the thread is on a Mutex's waiter queue.
struct SynchWaitParams {
- SynchWaitParams(Mutex::MuHow how_arg, const Condition *cond_arg,
- KernelTimeout timeout_arg, Mutex *cvmu_arg,
- PerThreadSynch *thread_arg,
- std::atomic<intptr_t> *cv_word_arg)
+ SynchWaitParams(Mutex::MuHow how_arg, const Condition* cond_arg,
+ KernelTimeout timeout_arg, Mutex* cvmu_arg,
+ PerThreadSynch* thread_arg,
+ std::atomic<intptr_t>* cv_word_arg)
: how(how_arg),
cond(cond_arg),
timeout(timeout_arg),
cvmu(cvmu_arg),
thread(thread_arg),
cv_word(cv_word_arg),
- contention_start_cycles(base_internal::CycleClock::Now()),
+ contention_start_cycles(CycleClock::Now()),
should_submit_contention_data(false) {}
const Mutex::MuHow how; // How this thread needs to wait.
- const Condition *cond; // The condition that this thread is waiting for.
- // In Mutex, this field is set to zero if a timeout
- // expires.
+ const Condition* cond; // The condition that this thread is waiting for.
+ // In Mutex, this field is set to zero if a timeout
+ // expires.
KernelTimeout timeout; // timeout expiry---absolute time
// In Mutex, this field is set to zero if a timeout
// expires.
- Mutex *const cvmu; // used for transfer from cond var to mutex
- PerThreadSynch *const thread; // thread that is waiting
+ Mutex* const cvmu; // used for transfer from cond var to mutex
+ PerThreadSynch* const thread; // thread that is waiting
// If not null, thread should be enqueued on the CondVar whose state
// word is cv_word instead of queueing normally on the Mutex.
- std::atomic<intptr_t> *cv_word;
+ std::atomic<intptr_t>* cv_word;
int64_t contention_start_cycles; // Time (in cycles) when this thread started
// to contend for the mutex.
@@ -537,12 +526,12 @@ struct SynchWaitParams {
};
struct SynchLocksHeld {
- int n; // number of valid entries in locks[]
- bool overflow; // true iff we overflowed the array at some point
+ int n; // number of valid entries in locks[]
+ bool overflow; // true iff we overflowed the array at some point
struct {
- Mutex *mu; // lock acquired
- int32_t count; // times acquired
- GraphId id; // deadlock_graph id of acquired lock
+ Mutex* mu; // lock acquired
+ int32_t count; // times acquired
+ GraphId id; // deadlock_graph id of acquired lock
} locks[40];
// If a thread overfills the array during deadlock detection, we
// continue, discarding information as needed. If no overflow has
@@ -552,11 +541,11 @@ struct SynchLocksHeld {
// A sentinel value in lists that is not 0.
// A 0 value is used to mean "not on a list".
-static PerThreadSynch *const kPerThreadSynchNull =
- reinterpret_cast<PerThreadSynch *>(1);
+static PerThreadSynch* const kPerThreadSynchNull =
+ reinterpret_cast<PerThreadSynch*>(1);
-static SynchLocksHeld *LocksHeldAlloc() {
- SynchLocksHeld *ret = reinterpret_cast<SynchLocksHeld *>(
+static SynchLocksHeld* LocksHeldAlloc() {
+ SynchLocksHeld* ret = reinterpret_cast<SynchLocksHeld*>(
base_internal::LowLevelAlloc::Alloc(sizeof(SynchLocksHeld)));
ret->n = 0;
ret->overflow = false;
@@ -564,24 +553,24 @@ static SynchLocksHeld *LocksHeldAlloc() {
}
// Return the PerThreadSynch-struct for this thread.
-static PerThreadSynch *Synch_GetPerThread() {
- ThreadIdentity *identity = GetOrCreateCurrentThreadIdentity();
+static PerThreadSynch* Synch_GetPerThread() {
+ ThreadIdentity* identity = GetOrCreateCurrentThreadIdentity();
return &identity->per_thread_synch;
}
-static PerThreadSynch *Synch_GetPerThreadAnnotated(Mutex *mu) {
+static PerThreadSynch* Synch_GetPerThreadAnnotated(Mutex* mu) {
if (mu) {
ABSL_TSAN_MUTEX_PRE_DIVERT(mu, 0);
}
- PerThreadSynch *w = Synch_GetPerThread();
+ PerThreadSynch* w = Synch_GetPerThread();
if (mu) {
ABSL_TSAN_MUTEX_POST_DIVERT(mu, 0);
}
return w;
}
-static SynchLocksHeld *Synch_GetAllLocks() {
- PerThreadSynch *s = Synch_GetPerThread();
+static SynchLocksHeld* Synch_GetAllLocks() {
+ PerThreadSynch* s = Synch_GetPerThread();
if (s->all_locks == nullptr) {
s->all_locks = LocksHeldAlloc(); // Freed by ReclaimThreadIdentity.
}
@@ -589,7 +578,7 @@ static SynchLocksHeld *Synch_GetAllLocks() {
}
// Post on "w"'s associated PerThreadSem.
-void Mutex::IncrementSynchSem(Mutex *mu, PerThreadSynch *w) {
+void Mutex::IncrementSynchSem(Mutex* mu, PerThreadSynch* w) {
if (mu) {
ABSL_TSAN_MUTEX_PRE_DIVERT(mu, 0);
// We miss synchronization around passing PerThreadSynch between threads
@@ -605,7 +594,7 @@ void Mutex::IncrementSynchSem(Mutex *mu, PerThreadSynch *w) {
}
// Wait on "w"'s associated PerThreadSem; returns false if timeout expired.
-bool Mutex::DecrementSynchSem(Mutex *mu, PerThreadSynch *w, KernelTimeout t) {
+bool Mutex::DecrementSynchSem(Mutex* mu, PerThreadSynch* w, KernelTimeout t) {
if (mu) {
ABSL_TSAN_MUTEX_PRE_DIVERT(mu, 0);
}
@@ -626,7 +615,7 @@ bool Mutex::DecrementSynchSem(Mutex *mu, PerThreadSynch *w, KernelTimeout t) {
// Mutex code checking that the "waitp" field has not been reused.
void Mutex::InternalAttemptToUseMutexInFatalSignalHandler() {
// Fix the per-thread state only if it exists.
- ThreadIdentity *identity = CurrentThreadIdentityIfPresent();
+ ThreadIdentity* identity = CurrentThreadIdentityIfPresent();
if (identity != nullptr) {
identity->per_thread_synch.suppress_fatal_errors = true;
}
@@ -635,21 +624,6 @@ void Mutex::InternalAttemptToUseMutexInFatalSignalHandler() {
std::memory_order_release);
}
-// --------------------------time support
-
-// Return the current time plus the timeout. Use the same clock as
-// PerThreadSem::Wait() for consistency. Unfortunately, we don't have
-// such a choice when a deadline is given directly.
-static absl::Time DeadlineFromTimeout(absl::Duration timeout) {
-#ifndef _WIN32
- struct timeval tv;
- gettimeofday(&tv, nullptr);
- return absl::TimeFromTimeval(tv) + timeout;
-#else
- return absl::Now() + timeout;
-#endif
-}
-
// --------------------------Mutexes
// In the layout below, the msb of the bottom byte is currently unused. Also,
@@ -660,24 +634,29 @@ static absl::Time DeadlineFromTimeout(absl::Duration timeout) {
// bit-twiddling trick in Mutex::Unlock().
// o kMuWriter / kMuReader == kMuWrWait / kMuWait,
// to enable the bit-twiddling trick in CheckForMutexCorruption().
-static const intptr_t kMuReader = 0x0001L; // a reader holds the lock
-static const intptr_t kMuDesig = 0x0002L; // there's a designated waker
-static const intptr_t kMuWait = 0x0004L; // threads are waiting
-static const intptr_t kMuWriter = 0x0008L; // a writer holds the lock
-static const intptr_t kMuEvent = 0x0010L; // record this mutex's events
+static const intptr_t kMuReader = 0x0001L; // a reader holds the lock
+// There's a designated waker.
// INVARIANT1: there's a thread that was blocked on the mutex, is
// no longer, yet has not yet acquired the mutex. If there's a
// designated waker, all threads can avoid taking the slow path in
// unlock because the designated waker will subsequently acquire
// the lock and wake someone. To maintain INVARIANT1 the bit is
// set when a thread is unblocked(INV1a), and threads that were
-// unblocked reset the bit when they either acquire or re-block
-// (INV1b).
-static const intptr_t kMuWrWait = 0x0020L; // runnable writer is waiting
- // for a reader
-static const intptr_t kMuSpin = 0x0040L; // spinlock protects wait list
-static const intptr_t kMuLow = 0x00ffL; // mask all mutex bits
-static const intptr_t kMuHigh = ~kMuLow; // mask pointer/reader count
+// unblocked reset the bit when they either acquire or re-block (INV1b).
+static const intptr_t kMuDesig = 0x0002L;
+static const intptr_t kMuWait = 0x0004L; // threads are waiting
+static const intptr_t kMuWriter = 0x0008L; // a writer holds the lock
+static const intptr_t kMuEvent = 0x0010L; // record this mutex's events
+// Runnable writer is waiting for a reader.
+// If set, new readers will not lock the mutex to avoid writer starvation.
+// Note: if a reader has higher priority than the writer, it will still lock
+// the mutex ahead of the waiting writer, but in a very inefficient manner:
+// the reader will first queue itself and block, but then the last unlocking
+// reader will wake it.
+static const intptr_t kMuWrWait = 0x0020L;
+static const intptr_t kMuSpin = 0x0040L; // spinlock protects wait list
+static const intptr_t kMuLow = 0x00ffL; // mask all mutex bits
+static const intptr_t kMuHigh = ~kMuLow; // mask pointer/reader count
// Hack to make constant values available to gdb pretty printer
enum {
@@ -773,8 +752,8 @@ Mutex::~Mutex() {
ABSL_TSAN_MUTEX_DESTROY(this, __tsan_mutex_not_static);
}
-void Mutex::EnableDebugLog(const char *name) {
- SynchEvent *e = EnsureSynchEvent(&this->mu_, name, kMuEvent, kMuSpin);
+void Mutex::EnableDebugLog(const char* name) {
+ SynchEvent* e = EnsureSynchEvent(&this->mu_, name, kMuEvent, kMuSpin);
e->log = true;
UnrefSynchEvent(e);
}
@@ -783,11 +762,10 @@ void EnableMutexInvariantDebugging(bool enabled) {
synch_check_invariants.store(enabled, std::memory_order_release);
}
-void Mutex::EnableInvariantDebugging(void (*invariant)(void *),
- void *arg) {
+void Mutex::EnableInvariantDebugging(void (*invariant)(void*), void* arg) {
if (synch_check_invariants.load(std::memory_order_acquire) &&
invariant != nullptr) {
- SynchEvent *e = EnsureSynchEvent(&this->mu_, nullptr, kMuEvent, kMuSpin);
+ SynchEvent* e = EnsureSynchEvent(&this->mu_, nullptr, kMuEvent, kMuSpin);
e->invariant = invariant;
e->arg = arg;
UnrefSynchEvent(e);
@@ -803,15 +781,15 @@ void SetMutexDeadlockDetectionMode(OnDeadlockCycle mode) {
// waiters with the same condition, type of lock, and thread priority.
//
// Requires that x and y be waiting on the same Mutex queue.
-static bool MuEquivalentWaiter(PerThreadSynch *x, PerThreadSynch *y) {
+static bool MuEquivalentWaiter(PerThreadSynch* x, PerThreadSynch* y) {
return x->waitp->how == y->waitp->how && x->priority == y->priority &&
Condition::GuaranteedEqual(x->waitp->cond, y->waitp->cond);
}
// Given the contents of a mutex word containing a PerThreadSynch pointer,
// return the pointer.
-static inline PerThreadSynch *GetPerThreadSynch(intptr_t v) {
- return reinterpret_cast<PerThreadSynch *>(v & kMuHigh);
+static inline PerThreadSynch* GetPerThreadSynch(intptr_t v) {
+ return reinterpret_cast<PerThreadSynch*>(v & kMuHigh);
}
// The next several routines maintain the per-thread next and skip fields
@@ -869,17 +847,17 @@ static inline PerThreadSynch *GetPerThreadSynch(intptr_t v) {
// except those in the added node and the former "head" node. This implies
// that the new node is added after head, and so must be the new head or the
// new front of the queue.
-static PerThreadSynch *Skip(PerThreadSynch *x) {
- PerThreadSynch *x0 = nullptr;
- PerThreadSynch *x1 = x;
- PerThreadSynch *x2 = x->skip;
+static PerThreadSynch* Skip(PerThreadSynch* x) {
+ PerThreadSynch* x0 = nullptr;
+ PerThreadSynch* x1 = x;
+ PerThreadSynch* x2 = x->skip;
if (x2 != nullptr) {
// Each iteration attempts to advance sequence (x0,x1,x2) to next sequence
// such that x1 == x0->skip && x2 == x1->skip
while ((x0 = x1, x1 = x2, x2 = x2->skip) != nullptr) {
- x0->skip = x2; // short-circuit skip from x0 to x2
+ x0->skip = x2; // short-circuit skip from x0 to x2
}
- x->skip = x1; // short-circuit skip from x to result
+ x->skip = x1; // short-circuit skip from x to result
}
return x1;
}
@@ -888,7 +866,7 @@ static PerThreadSynch *Skip(PerThreadSynch *x) {
// The latter is going to be removed out of order, because of a timeout.
// Check whether "ancestor" has a skip field pointing to "to_be_removed",
// and fix it if it does.
-static void FixSkip(PerThreadSynch *ancestor, PerThreadSynch *to_be_removed) {
+static void FixSkip(PerThreadSynch* ancestor, PerThreadSynch* to_be_removed) {
if (ancestor->skip == to_be_removed) { // ancestor->skip left dangling
if (to_be_removed->skip != nullptr) {
ancestor->skip = to_be_removed->skip; // can skip past to_be_removed
@@ -900,7 +878,7 @@ static void FixSkip(PerThreadSynch *ancestor, PerThreadSynch *to_be_removed) {
}
}
-static void CondVarEnqueue(SynchWaitParams *waitp);
+static void CondVarEnqueue(SynchWaitParams* waitp);
// Enqueue thread "waitp->thread" on a waiter queue.
// Called with mutex spinlock held if head != nullptr
@@ -921,8 +899,8 @@ static void CondVarEnqueue(SynchWaitParams *waitp);
// returned. This mechanism is used by CondVar to queue a thread on the
// condition variable queue instead of the mutex queue in implementing Wait().
// In this case, Enqueue() can return nullptr (if head==nullptr).
-static PerThreadSynch *Enqueue(PerThreadSynch *head,
- SynchWaitParams *waitp, intptr_t mu, int flags) {
+static PerThreadSynch* Enqueue(PerThreadSynch* head, SynchWaitParams* waitp,
+ intptr_t mu, int flags) {
// If we have been given a cv_word, call CondVarEnqueue() and return
// the previous head of the Mutex waiter queue.
if (waitp->cv_word != nullptr) {
@@ -930,42 +908,43 @@ static PerThreadSynch *Enqueue(PerThreadSynch *head,
return head;
}
- PerThreadSynch *s = waitp->thread;
+ PerThreadSynch* s = waitp->thread;
ABSL_RAW_CHECK(
s->waitp == nullptr || // normal case
s->waitp == waitp || // Fer()---transfer from condition variable
s->suppress_fatal_errors,
"detected illegal recursion into Mutex code");
s->waitp = waitp;
- s->skip = nullptr; // maintain skip invariant (see above)
- s->may_skip = true; // always true on entering queue
- s->wake = false; // not being woken
+ s->skip = nullptr; // maintain skip invariant (see above)
+ s->may_skip = true; // always true on entering queue
+ s->wake = false; // not being woken
s->cond_waiter = ((flags & kMuIsCond) != 0);
+#ifdef ABSL_HAVE_PTHREAD_GETSCHEDPARAM
+ int64_t now_cycles = CycleClock::Now();
+ if (s->next_priority_read_cycles < now_cycles) {
+ // Every so often, update our idea of the thread's priority.
+ // pthread_getschedparam() is 5% of the block/wakeup time;
+ // CycleClock::Now() is 0.5%.
+ int policy;
+ struct sched_param param;
+ const int err = pthread_getschedparam(pthread_self(), &policy, &param);
+ if (err != 0) {
+ ABSL_RAW_LOG(ERROR, "pthread_getschedparam failed: %d", err);
+ } else {
+ s->priority = param.sched_priority;
+ s->next_priority_read_cycles =
+ now_cycles + static_cast<int64_t>(CycleClock::Frequency());
+ }
+ }
+#endif
if (head == nullptr) { // s is the only waiter
s->next = s; // it's the only entry in the cycle
s->readers = mu; // reader count is from mu word
s->maybe_unlocking = false; // no one is searching an empty list
head = s; // s is new head
} else {
- PerThreadSynch *enqueue_after = nullptr; // we'll put s after this element
+ PerThreadSynch* enqueue_after = nullptr; // we'll put s after this element
#ifdef ABSL_HAVE_PTHREAD_GETSCHEDPARAM
- int64_t now_cycles = base_internal::CycleClock::Now();
- if (s->next_priority_read_cycles < now_cycles) {
- // Every so often, update our idea of the thread's priority.
- // pthread_getschedparam() is 5% of the block/wakeup time;
- // base_internal::CycleClock::Now() is 0.5%.
- int policy;
- struct sched_param param;
- const int err = pthread_getschedparam(pthread_self(), &policy, &param);
- if (err != 0) {
- ABSL_RAW_LOG(ERROR, "pthread_getschedparam failed: %d", err);
- } else {
- s->priority = param.sched_priority;
- s->next_priority_read_cycles =
- now_cycles +
- static_cast<int64_t>(base_internal::CycleClock::Frequency());
- }
- }
if (s->priority > head->priority) { // s's priority is above head's
// try to put s in priority-fifo order, or failing that at the front.
if (!head->maybe_unlocking) {
@@ -975,20 +954,20 @@ static PerThreadSynch *Enqueue(PerThreadSynch *head,
// Within a skip chain, all waiters have the same priority, so we can
// skip forward through the chains until we find one with a lower
// priority than the waiter to be enqueued.
- PerThreadSynch *advance_to = head; // next value of enqueue_after
+ PerThreadSynch* advance_to = head; // next value of enqueue_after
do {
enqueue_after = advance_to;
// (side-effect: optimizes skip chain)
advance_to = Skip(enqueue_after->next);
} while (s->priority <= advance_to->priority);
- // termination guaranteed because s->priority > head->priority
- // and head is the end of a skip chain
+ // termination guaranteed because s->priority > head->priority
+ // and head is the end of a skip chain
} else if (waitp->how == kExclusive &&
Condition::GuaranteedEqual(waitp->cond, nullptr)) {
// An unlocker could be scanning the queue, but we know it will recheck
// the queue front for writers that have no condition, which is what s
// is, so an insert at front is safe.
- enqueue_after = head; // add after head, at front
+ enqueue_after = head; // add after head, at front
}
}
#endif
@@ -1013,12 +992,12 @@ static PerThreadSynch *Enqueue(PerThreadSynch *head,
enqueue_after->skip = enqueue_after->next;
}
if (MuEquivalentWaiter(s, s->next)) { // s->may_skip is known to be true
- s->skip = s->next; // s may skip to its successor
+ s->skip = s->next; // s may skip to its successor
}
- } else { // enqueue not done any other way, so
- // we're inserting s at the back
+ } else { // enqueue not done any other way, so
+ // we're inserting s at the back
// s will become new head; copy data from head into it
- s->next = head->next; // add s after head
+ s->next = head->next; // add s after head
head->next = s;
s->readers = head->readers; // reader count is from previous head
s->maybe_unlocking = head->maybe_unlocking; // same for unlock hint
@@ -1037,17 +1016,17 @@ static PerThreadSynch *Enqueue(PerThreadSynch *head,
// whose last element is head. The new head element is returned, or null
// if the list is made empty.
// Dequeue is called with both spinlock and Mutex held.
-static PerThreadSynch *Dequeue(PerThreadSynch *head, PerThreadSynch *pw) {
- PerThreadSynch *w = pw->next;
- pw->next = w->next; // snip w out of list
- if (head == w) { // we removed the head
+static PerThreadSynch* Dequeue(PerThreadSynch* head, PerThreadSynch* pw) {
+ PerThreadSynch* w = pw->next;
+ pw->next = w->next; // snip w out of list
+ if (head == w) { // we removed the head
head = (pw == w) ? nullptr : pw; // either emptied list, or pw is new head
} else if (pw != head && MuEquivalentWaiter(pw, pw->next)) {
// pw can skip to its new successor
if (pw->next->skip !=
nullptr) { // either skip to its successors skip target
pw->skip = pw->next->skip;
- } else { // or to pw's successor
+ } else { // or to pw's successor
pw->skip = pw->next;
}
}
@@ -1060,27 +1039,27 @@ static PerThreadSynch *Dequeue(PerThreadSynch *head, PerThreadSynch *pw) {
// singly-linked list wake_list in the order found. Assumes that
// there is only one such element if the element has how == kExclusive.
// Return the new head.
-static PerThreadSynch *DequeueAllWakeable(PerThreadSynch *head,
- PerThreadSynch *pw,
- PerThreadSynch **wake_tail) {
- PerThreadSynch *orig_h = head;
- PerThreadSynch *w = pw->next;
+static PerThreadSynch* DequeueAllWakeable(PerThreadSynch* head,
+ PerThreadSynch* pw,
+ PerThreadSynch** wake_tail) {
+ PerThreadSynch* orig_h = head;
+ PerThreadSynch* w = pw->next;
bool skipped = false;
do {
- if (w->wake) { // remove this element
+ if (w->wake) { // remove this element
ABSL_RAW_CHECK(pw->skip == nullptr, "bad skip in DequeueAllWakeable");
// we're removing pw's successor so either pw->skip is zero or we should
// already have removed pw since if pw->skip!=null, pw has the same
// condition as w.
head = Dequeue(head, pw);
- w->next = *wake_tail; // keep list terminated
- *wake_tail = w; // add w to wake_list;
- wake_tail = &w->next; // next addition to end
+ w->next = *wake_tail; // keep list terminated
+ *wake_tail = w; // add w to wake_list;
+ wake_tail = &w->next; // next addition to end
if (w->waitp->how == kExclusive) { // wake at most 1 writer
break;
}
- } else { // not waking this one; skip
- pw = Skip(w); // skip as much as possible
+ } else { // not waking this one; skip
+ pw = Skip(w); // skip as much as possible
skipped = true;
}
w = pw->next;
@@ -1098,7 +1077,7 @@ static PerThreadSynch *DequeueAllWakeable(PerThreadSynch *head,
// Try to remove thread s from the list of waiters on this mutex.
// Does nothing if s is not on the waiter list.
-void Mutex::TryRemove(PerThreadSynch *s) {
+void Mutex::TryRemove(PerThreadSynch* s) {
SchedulingGuard::ScopedDisable disable_rescheduling;
intptr_t v = mu_.load(std::memory_order_relaxed);
// acquire spinlock & lock
@@ -1106,16 +1085,16 @@ void Mutex::TryRemove(PerThreadSynch *s) {
mu_.compare_exchange_strong(v, v | kMuSpin | kMuWriter,
std::memory_order_acquire,
std::memory_order_relaxed)) {
- PerThreadSynch *h = GetPerThreadSynch(v);
+ PerThreadSynch* h = GetPerThreadSynch(v);
if (h != nullptr) {
- PerThreadSynch *pw = h; // pw is w's predecessor
- PerThreadSynch *w;
+ PerThreadSynch* pw = h; // pw is w's predecessor
+ PerThreadSynch* w;
if ((w = pw->next) != s) { // search for thread,
do { // processing at least one element
// If the current element isn't equivalent to the waiter to be
// removed, we can skip the entire chain.
if (!MuEquivalentWaiter(s, w)) {
- pw = Skip(w); // so skip all that won't match
+ pw = Skip(w); // so skip all that won't match
// we don't have to worry about dangling skip fields
// in the threads we skipped; none can point to s
// because they are in a different equivalence class.
@@ -1127,7 +1106,7 @@ void Mutex::TryRemove(PerThreadSynch *s) {
// process the first thread again.
} while ((w = pw->next) != s && pw != h);
}
- if (w == s) { // found thread; remove it
+ if (w == s) { // found thread; remove it
// pw->skip may be non-zero here; the loop above ensured that
// no ancestor of s can skip to s, so removal is safe anyway.
h = Dequeue(h, pw);
@@ -1136,16 +1115,15 @@ void Mutex::TryRemove(PerThreadSynch *s) {
}
}
intptr_t nv;
- do { // release spinlock and lock
+ do { // release spinlock and lock
v = mu_.load(std::memory_order_relaxed);
nv = v & (kMuDesig | kMuEvent);
if (h != nullptr) {
nv |= kMuWait | reinterpret_cast<intptr_t>(h);
- h->readers = 0; // we hold writer lock
+ h->readers = 0; // we hold writer lock
h->maybe_unlocking = false; // finished unlocking
}
- } while (!mu_.compare_exchange_weak(v, nv,
- std::memory_order_release,
+ } while (!mu_.compare_exchange_weak(v, nv, std::memory_order_release,
std::memory_order_relaxed));
}
}
@@ -1155,7 +1133,7 @@ void Mutex::TryRemove(PerThreadSynch *s) {
// if the wait extends past the absolute time specified, even if "s" is still
// on the mutex queue. In this case, remove "s" from the queue and return
// true, otherwise return false.
-void Mutex::Block(PerThreadSynch *s) {
+void Mutex::Block(PerThreadSynch* s) {
while (s->state.load(std::memory_order_acquire) == PerThreadSynch::kQueued) {
if (!DecrementSynchSem(this, s, s->waitp->timeout)) {
// After a timeout, we go into a spin loop until we remove ourselves
@@ -1174,7 +1152,7 @@ void Mutex::Block(PerThreadSynch *s) {
// is not on the queue.
this->TryRemove(s);
}
- s->waitp->timeout = KernelTimeout::Never(); // timeout is satisfied
+ s->waitp->timeout = KernelTimeout::Never(); // timeout is satisfied
s->waitp->cond = nullptr; // condition no longer relevant for wakeups
}
}
@@ -1184,8 +1162,8 @@ void Mutex::Block(PerThreadSynch *s) {
}
// Wake thread w, and return the next thread in the list.
-PerThreadSynch *Mutex::Wakeup(PerThreadSynch *w) {
- PerThreadSynch *next = w->next;
+PerThreadSynch* Mutex::Wakeup(PerThreadSynch* w) {
+ PerThreadSynch* next = w->next;
w->next = nullptr;
w->state.store(PerThreadSynch::kAvailable, std::memory_order_release);
IncrementSynchSem(this, w);
@@ -1193,7 +1171,7 @@ PerThreadSynch *Mutex::Wakeup(PerThreadSynch *w) {
return next;
}
-static GraphId GetGraphIdLocked(Mutex *mu)
+static GraphId GetGraphIdLocked(Mutex* mu)
ABSL_EXCLUSIVE_LOCKS_REQUIRED(deadlock_graph_mu) {
if (!deadlock_graph) { // (re)create the deadlock graph.
deadlock_graph =
@@ -1203,7 +1181,7 @@ static GraphId GetGraphIdLocked(Mutex *mu)
return deadlock_graph->GetId(mu);
}
-static GraphId GetGraphId(Mutex *mu) ABSL_LOCKS_EXCLUDED(deadlock_graph_mu) {
+static GraphId GetGraphId(Mutex* mu) ABSL_LOCKS_EXCLUDED(deadlock_graph_mu) {
deadlock_graph_mu.Lock();
GraphId id = GetGraphIdLocked(mu);
deadlock_graph_mu.Unlock();
@@ -1213,7 +1191,7 @@ static GraphId GetGraphId(Mutex *mu) ABSL_LOCKS_EXCLUDED(deadlock_graph_mu) {
// Record a lock acquisition. This is used in debug mode for deadlock
// detection. The held_locks pointer points to the relevant data
// structure for each case.
-static void LockEnter(Mutex* mu, GraphId id, SynchLocksHeld *held_locks) {
+static void LockEnter(Mutex* mu, GraphId id, SynchLocksHeld* held_locks) {
int n = held_locks->n;
int i = 0;
while (i != n && held_locks->locks[i].id != id) {
@@ -1237,7 +1215,7 @@ static void LockEnter(Mutex* mu, GraphId id, SynchLocksHeld *held_locks) {
// eventually followed by a call to LockLeave(mu, id, x) by the same thread.
// It does not process the event if is not needed when deadlock detection is
// disabled.
-static void LockLeave(Mutex* mu, GraphId id, SynchLocksHeld *held_locks) {
+static void LockLeave(Mutex* mu, GraphId id, SynchLocksHeld* held_locks) {
int n = held_locks->n;
int i = 0;
while (i != n && held_locks->locks[i].id != id) {
@@ -1252,11 +1230,11 @@ static void LockLeave(Mutex* mu, GraphId id, SynchLocksHeld *held_locks) {
i++;
}
if (i == n) { // mu missing means releasing unheld lock
- SynchEvent *mu_events = GetSynchEvent(mu);
+ SynchEvent* mu_events = GetSynchEvent(mu);
ABSL_RAW_LOG(FATAL,
"thread releasing lock it does not hold: %p %s; "
,
- static_cast<void *>(mu),
+ static_cast<void*>(mu),
mu_events == nullptr ? "" : mu_events->name);
}
}
@@ -1273,7 +1251,7 @@ static void LockLeave(Mutex* mu, GraphId id, SynchLocksHeld *held_locks) {
}
// Call LockEnter() if in debug mode and deadlock detection is enabled.
-static inline void DebugOnlyLockEnter(Mutex *mu) {
+static inline void DebugOnlyLockEnter(Mutex* mu) {
if (kDebugMode) {
if (synch_deadlock_detection.load(std::memory_order_acquire) !=
OnDeadlockCycle::kIgnore) {
@@ -1283,7 +1261,7 @@ static inline void DebugOnlyLockEnter(Mutex *mu) {
}
// Call LockEnter() if in debug mode and deadlock detection is enabled.
-static inline void DebugOnlyLockEnter(Mutex *mu, GraphId id) {
+static inline void DebugOnlyLockEnter(Mutex* mu, GraphId id) {
if (kDebugMode) {
if (synch_deadlock_detection.load(std::memory_order_acquire) !=
OnDeadlockCycle::kIgnore) {
@@ -1293,7 +1271,7 @@ static inline void DebugOnlyLockEnter(Mutex *mu, GraphId id) {
}
// Call LockLeave() if in debug mode and deadlock detection is enabled.
-static inline void DebugOnlyLockLeave(Mutex *mu) {
+static inline void DebugOnlyLockLeave(Mutex* mu) {
if (kDebugMode) {
if (synch_deadlock_detection.load(std::memory_order_acquire) !=
OnDeadlockCycle::kIgnore) {
@@ -1302,9 +1280,9 @@ static inline void DebugOnlyLockLeave(Mutex *mu) {
}
}
-static char *StackString(void **pcs, int n, char *buf, int maxlen,
+static char* StackString(void** pcs, int n, char* buf, int maxlen,
bool symbolize) {
- static const int kSymLen = 200;
+ static constexpr int kSymLen = 200;
char sym[kSymLen];
int len = 0;
for (int i = 0; i != n; i++) {
@@ -1312,7 +1290,7 @@ static char *StackString(void **pcs, int n, char *buf, int maxlen,
return buf;
size_t count = static_cast<size_t>(maxlen - len);
if (symbolize) {
- if (!symbolizer(pcs[i], sym, kSymLen)) {
+ if (!absl::Symbolize(pcs[i], sym, kSymLen)) {
sym[0] = '\0';
}
snprintf(buf + len, count, "%s\t@ %p %s\n", (i == 0 ? "\n" : ""), pcs[i],
@@ -1325,15 +1303,17 @@ static char *StackString(void **pcs, int n, char *buf, int maxlen,
return buf;
}
-static char *CurrentStackString(char *buf, int maxlen, bool symbolize) {
- void *pcs[40];
+static char* CurrentStackString(char* buf, int maxlen, bool symbolize) {
+ void* pcs[40];
return StackString(pcs, absl::GetStackTrace(pcs, ABSL_ARRAYSIZE(pcs), 2), buf,
maxlen, symbolize);
}
namespace {
-enum { kMaxDeadlockPathLen = 10 }; // maximum length of a deadlock cycle;
- // a path this long would be remarkable
+enum {
+ kMaxDeadlockPathLen = 10
+}; // maximum length of a deadlock cycle;
+ // a path this long would be remarkable
// Buffers required to report a deadlock.
// We do not allocate them on stack to avoid large stack frame.
struct DeadlockReportBuffers {
@@ -1343,11 +1323,11 @@ struct DeadlockReportBuffers {
struct ScopedDeadlockReportBuffers {
ScopedDeadlockReportBuffers() {
- b = reinterpret_cast<DeadlockReportBuffers *>(
+ b = reinterpret_cast<DeadlockReportBuffers*>(
base_internal::LowLevelAlloc::Alloc(sizeof(*b)));
}
~ScopedDeadlockReportBuffers() { base_internal::LowLevelAlloc::Free(b); }
- DeadlockReportBuffers *b;
+ DeadlockReportBuffers* b;
};
// Helper to pass to GraphCycles::UpdateStackTrace.
@@ -1358,13 +1338,13 @@ int GetStack(void** stack, int max_depth) {
// Called in debug mode when a thread is about to acquire a lock in a way that
// may block.
-static GraphId DeadlockCheck(Mutex *mu) {
+static GraphId DeadlockCheck(Mutex* mu) {
if (synch_deadlock_detection.load(std::memory_order_acquire) ==
OnDeadlockCycle::kIgnore) {
return InvalidGraphId();
}
- SynchLocksHeld *all_locks = Synch_GetAllLocks();
+ SynchLocksHeld* all_locks = Synch_GetAllLocks();
absl::base_internal::SpinLockHolder lock(&deadlock_graph_mu);
const GraphId mu_id = GetGraphIdLocked(mu);
@@ -1386,8 +1366,8 @@ static GraphId DeadlockCheck(Mutex *mu) {
// For each other mutex already held by this thread:
for (int i = 0; i != all_locks->n; i++) {
const GraphId other_node_id = all_locks->locks[i].id;
- const Mutex *other =
- static_cast<const Mutex *>(deadlock_graph->Ptr(other_node_id));
+ const Mutex* other =
+ static_cast<const Mutex*>(deadlock_graph->Ptr(other_node_id));
if (other == nullptr) {
// Ignore stale lock
continue;
@@ -1396,7 +1376,7 @@ static GraphId DeadlockCheck(Mutex *mu) {
// Add the acquired-before edge to the graph.
if (!deadlock_graph->InsertEdge(other_node_id, mu_id)) {
ScopedDeadlockReportBuffers scoped_buffers;
- DeadlockReportBuffers *b = scoped_buffers.b;
+ DeadlockReportBuffers* b = scoped_buffers.b;
static int number_of_reported_deadlocks = 0;
number_of_reported_deadlocks++;
// Symbolize only 2 first deadlock report to avoid huge slowdowns.
@@ -1407,37 +1387,40 @@ static GraphId DeadlockCheck(Mutex *mu) {
for (int j = 0; j != all_locks->n; j++) {
void* pr = deadlock_graph->Ptr(all_locks->locks[j].id);
if (pr != nullptr) {
- snprintf(b->buf + len, sizeof (b->buf) - len, " %p", pr);
+ snprintf(b->buf + len, sizeof(b->buf) - len, " %p", pr);
len += strlen(&b->buf[len]);
}
}
ABSL_RAW_LOG(ERROR,
"Acquiring absl::Mutex %p while holding %s; a cycle in the "
"historical lock ordering graph has been observed",
- static_cast<void *>(mu), b->buf);
+ static_cast<void*>(mu), b->buf);
ABSL_RAW_LOG(ERROR, "Cycle: ");
- int path_len = deadlock_graph->FindPath(
- mu_id, other_node_id, ABSL_ARRAYSIZE(b->path), b->path);
- for (int j = 0; j != path_len; j++) {
+ int path_len = deadlock_graph->FindPath(mu_id, other_node_id,
+ ABSL_ARRAYSIZE(b->path), b->path);
+ for (int j = 0; j != path_len && j != ABSL_ARRAYSIZE(b->path); j++) {
GraphId id = b->path[j];
- Mutex *path_mu = static_cast<Mutex *>(deadlock_graph->Ptr(id));
+ Mutex* path_mu = static_cast<Mutex*>(deadlock_graph->Ptr(id));
if (path_mu == nullptr) continue;
void** stack;
int depth = deadlock_graph->GetStackTrace(id, &stack);
snprintf(b->buf, sizeof(b->buf),
- "mutex@%p stack: ", static_cast<void *>(path_mu));
+ "mutex@%p stack: ", static_cast<void*>(path_mu));
StackString(stack, depth, b->buf + strlen(b->buf),
static_cast<int>(sizeof(b->buf) - strlen(b->buf)),
symbolize);
ABSL_RAW_LOG(ERROR, "%s", b->buf);
}
+ if (path_len > static_cast<int>(ABSL_ARRAYSIZE(b->path))) {
+ ABSL_RAW_LOG(ERROR, "(long cycle; list truncated)");
+ }
if (synch_deadlock_detection.load(std::memory_order_acquire) ==
OnDeadlockCycle::kAbort) {
deadlock_graph_mu.Unlock(); // avoid deadlock in fatal sighandler
ABSL_RAW_LOG(FATAL, "dying due to potential deadlock");
return mu_id;
}
- break; // report at most one potential deadlock per acquisition
+ break; // report at most one potential deadlock per acquisition
}
}
@@ -1446,7 +1429,7 @@ static GraphId DeadlockCheck(Mutex *mu) {
// Invoke DeadlockCheck() iff we're in debug mode and
// deadlock checking has been enabled.
-static inline GraphId DebugOnlyDeadlockCheck(Mutex *mu) {
+static inline GraphId DebugOnlyDeadlockCheck(Mutex* mu) {
if (kDebugMode && synch_deadlock_detection.load(std::memory_order_acquire) !=
OnDeadlockCycle::kIgnore) {
return DeadlockCheck(mu);
@@ -1473,13 +1456,13 @@ void Mutex::AssertNotHeld() const {
(mu_.load(std::memory_order_relaxed) & (kMuWriter | kMuReader)) != 0 &&
synch_deadlock_detection.load(std::memory_order_acquire) !=
OnDeadlockCycle::kIgnore) {
- GraphId id = GetGraphId(const_cast<Mutex *>(this));
- SynchLocksHeld *locks = Synch_GetAllLocks();
+ GraphId id = GetGraphId(const_cast<Mutex*>(this));
+ SynchLocksHeld* locks = Synch_GetAllLocks();
for (int i = 0; i != locks->n; i++) {
if (locks->locks[i].id == id) {
- SynchEvent *mu_events = GetSynchEvent(this);
+ SynchEvent* mu_events = GetSynchEvent(this);
ABSL_RAW_LOG(FATAL, "thread should not hold mutex %p %s",
- static_cast<const void *>(this),
+ static_cast<const void*>(this),
(mu_events == nullptr ? "" : mu_events->name));
}
}
@@ -1492,8 +1475,8 @@ static bool TryAcquireWithSpinning(std::atomic<intptr_t>* mu) {
int c = GetMutexGlobals().spinloop_iterations;
do { // do/while somewhat faster on AMD
intptr_t v = mu->load(std::memory_order_relaxed);
- if ((v & (kMuReader|kMuEvent)) != 0) {
- return false; // a reader or tracing -> give up
+ if ((v & (kMuReader | kMuEvent)) != 0) {
+ return false; // a reader or tracing -> give up
} else if (((v & kMuWriter) == 0) && // no holder -> try to acquire
mu->compare_exchange_strong(v, kMuWriter | v,
std::memory_order_acquire,
@@ -1510,8 +1493,7 @@ void Mutex::Lock() {
intptr_t v = mu_.load(std::memory_order_relaxed);
// try fast acquire, then spin loop
if ((v & (kMuWriter | kMuReader | kMuEvent)) != 0 ||
- !mu_.compare_exchange_strong(v, kMuWriter | v,
- std::memory_order_acquire,
+ !mu_.compare_exchange_strong(v, kMuWriter | v, std::memory_order_acquire,
std::memory_order_relaxed)) {
// try spin acquire, then slow loop
if (!TryAcquireWithSpinning(&this->mu_)) {
@@ -1537,7 +1519,7 @@ void Mutex::ReaderLock() {
ABSL_TSAN_MUTEX_POST_LOCK(this, __tsan_mutex_read_lock, 0);
}
-void Mutex::LockWhen(const Condition &cond) {
+void Mutex::LockWhen(const Condition& cond) {
ABSL_TSAN_MUTEX_PRE_LOCK(this, 0);
GraphId id = DebugOnlyDeadlockCheck(this);
this->LockSlow(kExclusive, &cond, 0);
@@ -1545,21 +1527,26 @@ void Mutex::LockWhen(const Condition &cond) {
ABSL_TSAN_MUTEX_POST_LOCK(this, 0, 0);
}
-bool Mutex::LockWhenWithTimeout(const Condition &cond, absl::Duration timeout) {
- return LockWhenWithDeadline(cond, DeadlineFromTimeout(timeout));
+bool Mutex::LockWhenWithTimeout(const Condition& cond, absl::Duration timeout) {
+ ABSL_TSAN_MUTEX_PRE_LOCK(this, 0);
+ GraphId id = DebugOnlyDeadlockCheck(this);
+ bool res = LockSlowWithDeadline(kExclusive, &cond, KernelTimeout(timeout), 0);
+ DebugOnlyLockEnter(this, id);
+ ABSL_TSAN_MUTEX_POST_LOCK(this, 0, 0);
+ return res;
}
-bool Mutex::LockWhenWithDeadline(const Condition &cond, absl::Time deadline) {
+bool Mutex::LockWhenWithDeadline(const Condition& cond, absl::Time deadline) {
ABSL_TSAN_MUTEX_PRE_LOCK(this, 0);
GraphId id = DebugOnlyDeadlockCheck(this);
- bool res = LockSlowWithDeadline(kExclusive, &cond,
- KernelTimeout(deadline), 0);
+ bool res =
+ LockSlowWithDeadline(kExclusive, &cond, KernelTimeout(deadline), 0);
DebugOnlyLockEnter(this, id);
ABSL_TSAN_MUTEX_POST_LOCK(this, 0, 0);
return res;
}
-void Mutex::ReaderLockWhen(const Condition &cond) {
+void Mutex::ReaderLockWhen(const Condition& cond) {
ABSL_TSAN_MUTEX_PRE_LOCK(this, __tsan_mutex_read_lock);
GraphId id = DebugOnlyDeadlockCheck(this);
this->LockSlow(kShared, &cond, 0);
@@ -1567,12 +1554,17 @@ void Mutex::ReaderLockWhen(const Condition &cond) {
ABSL_TSAN_MUTEX_POST_LOCK(this, __tsan_mutex_read_lock, 0);
}
-bool Mutex::ReaderLockWhenWithTimeout(const Condition &cond,
+bool Mutex::ReaderLockWhenWithTimeout(const Condition& cond,
absl::Duration timeout) {
- return ReaderLockWhenWithDeadline(cond, DeadlineFromTimeout(timeout));
+ ABSL_TSAN_MUTEX_PRE_LOCK(this, __tsan_mutex_read_lock);
+ GraphId id = DebugOnlyDeadlockCheck(this);
+ bool res = LockSlowWithDeadline(kShared, &cond, KernelTimeout(timeout), 0);
+ DebugOnlyLockEnter(this, id);
+ ABSL_TSAN_MUTEX_POST_LOCK(this, __tsan_mutex_read_lock, 0);
+ return res;
}
-bool Mutex::ReaderLockWhenWithDeadline(const Condition &cond,
+bool Mutex::ReaderLockWhenWithDeadline(const Condition& cond,
absl::Time deadline) {
ABSL_TSAN_MUTEX_PRE_LOCK(this, __tsan_mutex_read_lock);
GraphId id = DebugOnlyDeadlockCheck(this);
@@ -1582,23 +1574,34 @@ bool Mutex::ReaderLockWhenWithDeadline(const Condition &cond,
return res;
}
-void Mutex::Await(const Condition &cond) {
- if (cond.Eval()) { // condition already true; nothing to do
+void Mutex::Await(const Condition& cond) {
+ if (cond.Eval()) { // condition already true; nothing to do
if (kDebugMode) {
this->AssertReaderHeld();
}
- } else { // normal case
+ } else { // normal case
ABSL_RAW_CHECK(this->AwaitCommon(cond, KernelTimeout::Never()),
"condition untrue on return from Await");
}
}
-bool Mutex::AwaitWithTimeout(const Condition &cond, absl::Duration timeout) {
- return AwaitWithDeadline(cond, DeadlineFromTimeout(timeout));
+bool Mutex::AwaitWithTimeout(const Condition& cond, absl::Duration timeout) {
+ if (cond.Eval()) { // condition already true; nothing to do
+ if (kDebugMode) {
+ this->AssertReaderHeld();
+ }
+ return true;
+ }
+
+ KernelTimeout t{timeout};
+ bool res = this->AwaitCommon(cond, t);
+ ABSL_RAW_CHECK(res || t.has_timeout(),
+ "condition untrue on return from Await");
+ return res;
}
-bool Mutex::AwaitWithDeadline(const Condition &cond, absl::Time deadline) {
- if (cond.Eval()) { // condition already true; nothing to do
+bool Mutex::AwaitWithDeadline(const Condition& cond, absl::Time deadline) {
+ if (cond.Eval()) { // condition already true; nothing to do
if (kDebugMode) {
this->AssertReaderHeld();
}
@@ -1612,14 +1615,14 @@ bool Mutex::AwaitWithDeadline(const Condition &cond, absl::Time deadline) {
return res;
}
-bool Mutex::AwaitCommon(const Condition &cond, KernelTimeout t) {
+bool Mutex::AwaitCommon(const Condition& cond, KernelTimeout t) {
this->AssertReaderHeld();
MuHow how =
(mu_.load(std::memory_order_relaxed) & kMuWriter) ? kExclusive : kShared;
ABSL_TSAN_MUTEX_PRE_UNLOCK(this, TsanFlags(how));
- SynchWaitParams waitp(
- how, &cond, t, nullptr /*no cvmu*/, Synch_GetPerThreadAnnotated(this),
- nullptr /*no cv_word*/);
+ SynchWaitParams waitp(how, &cond, t, nullptr /*no cvmu*/,
+ Synch_GetPerThreadAnnotated(this),
+ nullptr /*no cv_word*/);
int flags = kMuHasBlocked;
if (!Condition::GuaranteedEqual(&cond, nullptr)) {
flags |= kMuIsCond;
@@ -1639,14 +1642,13 @@ bool Mutex::TryLock() {
ABSL_TSAN_MUTEX_PRE_LOCK(this, __tsan_mutex_try_lock);
intptr_t v = mu_.load(std::memory_order_relaxed);
if ((v & (kMuWriter | kMuReader | kMuEvent)) == 0 && // try fast acquire
- mu_.compare_exchange_strong(v, kMuWriter | v,
- std::memory_order_acquire,
+ mu_.compare_exchange_strong(v, kMuWriter | v, std::memory_order_acquire,
std::memory_order_relaxed)) {
DebugOnlyLockEnter(this);
ABSL_TSAN_MUTEX_POST_LOCK(this, __tsan_mutex_try_lock, 0);
return true;
}
- if ((v & kMuEvent) != 0) { // we're recording events
+ if ((v & kMuEvent) != 0) { // we're recording events
if ((v & kExclusive->slow_need_zero) == 0 && // try fast acquire
mu_.compare_exchange_strong(
v, (kExclusive->fast_or | v) + kExclusive->fast_add,
@@ -1672,7 +1674,7 @@ bool Mutex::ReaderTryLock() {
// changing (typically because the reader count changes) under the CAS. We
// limit the number of attempts to avoid having to think about livelock.
int loop_limit = 5;
- while ((v & (kMuWriter|kMuWait|kMuEvent)) == 0 && loop_limit != 0) {
+ while ((v & (kMuWriter | kMuWait | kMuEvent)) == 0 && loop_limit != 0) {
if (mu_.compare_exchange_strong(v, (kMuReader | v) + kMuOne,
std::memory_order_acquire,
std::memory_order_relaxed)) {
@@ -1684,7 +1686,7 @@ bool Mutex::ReaderTryLock() {
loop_limit--;
v = mu_.load(std::memory_order_relaxed);
}
- if ((v & kMuEvent) != 0) { // we're recording events
+ if ((v & kMuEvent) != 0) { // we're recording events
loop_limit = 5;
while ((v & kShared->slow_need_zero) == 0 && loop_limit != 0) {
if (mu_.compare_exchange_strong(v, (kMuReader | v) + kMuOne,
@@ -1723,7 +1725,7 @@ void Mutex::Unlock() {
// should_try_cas is whether we'll try a compare-and-swap immediately.
// NOTE: optimized out when kDebugMode is false.
bool should_try_cas = ((v & (kMuEvent | kMuWriter)) == kMuWriter &&
- (v & (kMuWait | kMuDesig)) != kMuWait);
+ (v & (kMuWait | kMuDesig)) != kMuWait);
// But, we can use an alternate computation of it, that compilers
// currently don't find on their own. When that changes, this function
// can be simplified.
@@ -1740,10 +1742,9 @@ void Mutex::Unlock() {
static_cast<long long>(v), static_cast<long long>(x),
static_cast<long long>(y));
}
- if (x < y &&
- mu_.compare_exchange_strong(v, v & ~(kMuWrWait | kMuWriter),
- std::memory_order_release,
- std::memory_order_relaxed)) {
+ if (x < y && mu_.compare_exchange_strong(v, v & ~(kMuWrWait | kMuWriter),
+ std::memory_order_release,
+ std::memory_order_relaxed)) {
// fast writer release (writer with no waiters or with designated waker)
} else {
this->UnlockSlow(nullptr /*no waitp*/); // take slow path
@@ -1753,7 +1754,7 @@ void Mutex::Unlock() {
// Requires v to represent a reader-locked state.
static bool ExactlyOneReader(intptr_t v) {
- assert((v & (kMuWriter|kMuReader)) == kMuReader);
+ assert((v & (kMuWriter | kMuReader)) == kMuReader);
assert((v & kMuHigh) != 0);
// The more straightforward "(v & kMuHigh) == kMuOne" also works, but
// on some architectures the following generates slightly smaller code.
@@ -1766,12 +1767,11 @@ void Mutex::ReaderUnlock() {
ABSL_TSAN_MUTEX_PRE_UNLOCK(this, __tsan_mutex_read_lock);
DebugOnlyLockLeave(this);
intptr_t v = mu_.load(std::memory_order_relaxed);
- assert((v & (kMuWriter|kMuReader)) == kMuReader);
- if ((v & (kMuReader|kMuWait|kMuEvent)) == kMuReader) {
+ assert((v & (kMuWriter | kMuReader)) == kMuReader);
+ if ((v & (kMuReader | kMuWait | kMuEvent)) == kMuReader) {
// fast reader release (reader with no waiters)
- intptr_t clear = ExactlyOneReader(v) ? kMuReader|kMuOne : kMuOne;
- if (mu_.compare_exchange_strong(v, v - clear,
- std::memory_order_release,
+ intptr_t clear = ExactlyOneReader(v) ? kMuReader | kMuOne : kMuOne;
+ if (mu_.compare_exchange_strong(v, v - clear, std::memory_order_release,
std::memory_order_relaxed)) {
ABSL_TSAN_MUTEX_POST_UNLOCK(this, __tsan_mutex_read_lock);
return;
@@ -1810,7 +1810,7 @@ static intptr_t IgnoreWaitingWritersMask(int flag) {
}
// Internal version of LockWhen(). See LockSlowWithDeadline()
-ABSL_ATTRIBUTE_NOINLINE void Mutex::LockSlow(MuHow how, const Condition *cond,
+ABSL_ATTRIBUTE_NOINLINE void Mutex::LockSlow(MuHow how, const Condition* cond,
int flags) {
ABSL_RAW_CHECK(
this->LockSlowWithDeadline(how, cond, KernelTimeout::Never(), flags),
@@ -1818,7 +1818,7 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::LockSlow(MuHow how, const Condition *cond,
}
// Compute cond->Eval() and tell race detectors that we do it under mutex mu.
-static inline bool EvalConditionAnnotated(const Condition *cond, Mutex *mu,
+static inline bool EvalConditionAnnotated(const Condition* cond, Mutex* mu,
bool locking, bool trylock,
bool read_lock) {
// Delicate annotation dance.
@@ -1868,7 +1868,7 @@ static inline bool EvalConditionAnnotated(const Condition *cond, Mutex *mu,
// tsan). As the result there is no tsan-visible synchronization between the
// addition and this thread. So if we would enable race detection here,
// it would race with the predicate initialization.
-static inline bool EvalConditionIgnored(Mutex *mu, const Condition *cond) {
+static inline bool EvalConditionIgnored(Mutex* mu, const Condition* cond) {
// Memory accesses are already ignored inside of lock/unlock operations,
// but synchronization operations are also ignored. When we evaluate the
// predicate we must ignore only memory accesses but not synchronization,
@@ -1893,7 +1893,7 @@ static inline bool EvalConditionIgnored(Mutex *mu, const Condition *cond) {
// obstruct this call
// - kMuIsCond indicates that this is a conditional acquire (condition variable,
// Await, LockWhen) so contention profiling should be suppressed.
-bool Mutex::LockSlowWithDeadline(MuHow how, const Condition *cond,
+bool Mutex::LockSlowWithDeadline(MuHow how, const Condition* cond,
KernelTimeout t, int flags) {
intptr_t v = mu_.load(std::memory_order_relaxed);
bool unlock = false;
@@ -1910,9 +1910,9 @@ bool Mutex::LockSlowWithDeadline(MuHow how, const Condition *cond,
}
unlock = true;
}
- SynchWaitParams waitp(
- how, cond, t, nullptr /*no cvmu*/, Synch_GetPerThreadAnnotated(this),
- nullptr /*no cv_word*/);
+ SynchWaitParams waitp(how, cond, t, nullptr /*no cvmu*/,
+ Synch_GetPerThreadAnnotated(this),
+ nullptr /*no cv_word*/);
if (!Condition::GuaranteedEqual(cond, nullptr)) {
flags |= kMuIsCond;
}
@@ -1953,20 +1953,20 @@ static void CheckForMutexCorruption(intptr_t v, const char* label) {
if (ABSL_PREDICT_TRUE((w & (w << 3) & (kMuWriter | kMuWrWait)) == 0)) return;
RAW_CHECK_FMT((v & (kMuWriter | kMuReader)) != (kMuWriter | kMuReader),
"%s: Mutex corrupt: both reader and writer lock held: %p",
- label, reinterpret_cast<void *>(v));
+ label, reinterpret_cast<void*>(v));
RAW_CHECK_FMT((v & (kMuWait | kMuWrWait)) != kMuWrWait,
- "%s: Mutex corrupt: waiting writer with no waiters: %p",
- label, reinterpret_cast<void *>(v));
+ "%s: Mutex corrupt: waiting writer with no waiters: %p", label,
+ reinterpret_cast<void*>(v));
assert(false);
}
-void Mutex::LockSlowLoop(SynchWaitParams *waitp, int flags) {
+void Mutex::LockSlowLoop(SynchWaitParams* waitp, int flags) {
SchedulingGuard::ScopedDisable disable_rescheduling;
int c = 0;
intptr_t v = mu_.load(std::memory_order_relaxed);
if ((v & kMuEvent) != 0) {
- PostSynchEvent(this,
- waitp->how == kExclusive? SYNCH_EV_LOCK: SYNCH_EV_READERLOCK);
+ PostSynchEvent(
+ this, waitp->how == kExclusive ? SYNCH_EV_LOCK : SYNCH_EV_READERLOCK);
}
ABSL_RAW_CHECK(
waitp->thread->waitp == nullptr || waitp->thread->suppress_fatal_errors,
@@ -1991,11 +1991,11 @@ void Mutex::LockSlowLoop(SynchWaitParams *waitp, int flags) {
flags |= kMuHasBlocked;
c = 0;
}
- } else { // need to access waiter list
+ } else { // need to access waiter list
bool dowait = false;
- if ((v & (kMuSpin|kMuWait)) == 0) { // no waiters
+ if ((v & (kMuSpin | kMuWait)) == 0) { // no waiters
// This thread tries to become the one and only waiter.
- PerThreadSynch *new_h = Enqueue(nullptr, waitp, v, flags);
+ PerThreadSynch* new_h = Enqueue(nullptr, waitp, v, flags);
intptr_t nv =
(v & ClearDesignatedWakerMask(flags & kMuHasBlocked) & kMuLow) |
kMuWait;
@@ -2007,7 +2007,7 @@ void Mutex::LockSlowLoop(SynchWaitParams *waitp, int flags) {
v, reinterpret_cast<intptr_t>(new_h) | nv,
std::memory_order_release, std::memory_order_relaxed)) {
dowait = true;
- } else { // attempted Enqueue() failed
+ } else { // attempted Enqueue() failed
// zero out the waitp field set by Enqueue()
waitp->thread->waitp = nullptr;
}
@@ -2020,9 +2020,9 @@ void Mutex::LockSlowLoop(SynchWaitParams *waitp, int flags) {
(v & ClearDesignatedWakerMask(flags & kMuHasBlocked)) |
kMuSpin | kMuReader,
std::memory_order_acquire, std::memory_order_relaxed)) {
- PerThreadSynch *h = GetPerThreadSynch(v);
- h->readers += kMuOne; // inc reader count in waiter
- do { // release spinlock
+ PerThreadSynch* h = GetPerThreadSynch(v);
+ h->readers += kMuOne; // inc reader count in waiter
+ do { // release spinlock
v = mu_.load(std::memory_order_relaxed);
} while (!mu_.compare_exchange_weak(v, (v & ~kMuSpin) | kMuReader,
std::memory_order_release,
@@ -2032,7 +2032,7 @@ void Mutex::LockSlowLoop(SynchWaitParams *waitp, int flags) {
waitp->how == kShared)) {
break; // we timed out, or condition true, so return
}
- this->UnlockSlow(waitp); // got lock but condition false
+ this->UnlockSlow(waitp); // got lock but condition false
this->Block(waitp->thread);
flags |= kMuHasBlocked;
c = 0;
@@ -2043,18 +2043,19 @@ void Mutex::LockSlowLoop(SynchWaitParams *waitp, int flags) {
(v & ClearDesignatedWakerMask(flags & kMuHasBlocked)) |
kMuSpin | kMuWait,
std::memory_order_acquire, std::memory_order_relaxed)) {
- PerThreadSynch *h = GetPerThreadSynch(v);
- PerThreadSynch *new_h = Enqueue(h, waitp, v, flags);
+ PerThreadSynch* h = GetPerThreadSynch(v);
+ PerThreadSynch* new_h = Enqueue(h, waitp, v, flags);
intptr_t wr_wait = 0;
ABSL_RAW_CHECK(new_h != nullptr, "Enqueue to list failed");
if (waitp->how == kExclusive && (v & kMuReader) != 0) {
- wr_wait = kMuWrWait; // give priority to a waiting writer
+ wr_wait = kMuWrWait; // give priority to a waiting writer
}
- do { // release spinlock
+ do { // release spinlock
v = mu_.load(std::memory_order_relaxed);
} while (!mu_.compare_exchange_weak(
- v, (v & (kMuLow & ~kMuSpin)) | kMuWait | wr_wait |
- reinterpret_cast<intptr_t>(new_h),
+ v,
+ (v & (kMuLow & ~kMuSpin)) | kMuWait | wr_wait |
+ reinterpret_cast<intptr_t>(new_h),
std::memory_order_release, std::memory_order_relaxed));
dowait = true;
}
@@ -2074,9 +2075,9 @@ void Mutex::LockSlowLoop(SynchWaitParams *waitp, int flags) {
waitp->thread->waitp == nullptr || waitp->thread->suppress_fatal_errors,
"detected illegal recursion into Mutex code");
if ((v & kMuEvent) != 0) {
- PostSynchEvent(this,
- waitp->how == kExclusive? SYNCH_EV_LOCK_RETURNING :
- SYNCH_EV_READERLOCK_RETURNING);
+ PostSynchEvent(this, waitp->how == kExclusive
+ ? SYNCH_EV_LOCK_RETURNING
+ : SYNCH_EV_READERLOCK_RETURNING);
}
}
@@ -2085,28 +2086,28 @@ void Mutex::LockSlowLoop(SynchWaitParams *waitp, int flags) {
// which holds the lock but is not runnable because its condition is false
// or it is in the process of blocking on a condition variable; it must requeue
// itself on the mutex/condvar to wait for its condition to become true.
-ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
+ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams* waitp) {
SchedulingGuard::ScopedDisable disable_rescheduling;
intptr_t v = mu_.load(std::memory_order_relaxed);
this->AssertReaderHeld();
CheckForMutexCorruption(v, "Unlock");
if ((v & kMuEvent) != 0) {
- PostSynchEvent(this,
- (v & kMuWriter) != 0? SYNCH_EV_UNLOCK: SYNCH_EV_READERUNLOCK);
+ PostSynchEvent(
+ this, (v & kMuWriter) != 0 ? SYNCH_EV_UNLOCK : SYNCH_EV_READERUNLOCK);
}
int c = 0;
// the waiter under consideration to wake, or zero
- PerThreadSynch *w = nullptr;
+ PerThreadSynch* w = nullptr;
// the predecessor to w or zero
- PerThreadSynch *pw = nullptr;
+ PerThreadSynch* pw = nullptr;
// head of the list searched previously, or zero
- PerThreadSynch *old_h = nullptr;
+ PerThreadSynch* old_h = nullptr;
// a condition that's known to be false.
- const Condition *known_false = nullptr;
- PerThreadSynch *wake_list = kPerThreadSynchNull; // list of threads to wake
- intptr_t wr_wait = 0; // set to kMuWrWait if we wake a reader and a
- // later writer could have acquired the lock
- // (starvation avoidance)
+ const Condition* known_false = nullptr;
+ PerThreadSynch* wake_list = kPerThreadSynchNull; // list of threads to wake
+ intptr_t wr_wait = 0; // set to kMuWrWait if we wake a reader and a
+ // later writer could have acquired the lock
+ // (starvation avoidance)
ABSL_RAW_CHECK(waitp == nullptr || waitp->thread->waitp == nullptr ||
waitp->thread->suppress_fatal_errors,
"detected illegal recursion into Mutex code");
@@ -2126,8 +2127,7 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
} else if ((v & (kMuReader | kMuWait)) == kMuReader && waitp == nullptr) {
// fast reader release (reader with no waiters)
intptr_t clear = ExactlyOneReader(v) ? kMuReader | kMuOne : kMuOne;
- if (mu_.compare_exchange_strong(v, v - clear,
- std::memory_order_release,
+ if (mu_.compare_exchange_strong(v, v - clear, std::memory_order_release,
std::memory_order_relaxed)) {
return;
}
@@ -2135,16 +2135,16 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
mu_.compare_exchange_strong(v, v | kMuSpin,
std::memory_order_acquire,
std::memory_order_relaxed)) {
- if ((v & kMuWait) == 0) { // no one to wake
+ if ((v & kMuWait) == 0) { // no one to wake
intptr_t nv;
bool do_enqueue = true; // always Enqueue() the first time
ABSL_RAW_CHECK(waitp != nullptr,
"UnlockSlow is confused"); // about to sleep
- do { // must loop to release spinlock as reader count may change
+ do { // must loop to release spinlock as reader count may change
v = mu_.load(std::memory_order_relaxed);
// decrement reader count if there are readers
- intptr_t new_readers = (v >= kMuOne)? v - kMuOne : v;
- PerThreadSynch *new_h = nullptr;
+ intptr_t new_readers = (v >= kMuOne) ? v - kMuOne : v;
+ PerThreadSynch* new_h = nullptr;
if (do_enqueue) {
// If we are enqueuing on a CondVar (waitp->cv_word != nullptr) then
// we must not retry here. The initial attempt will always have
@@ -2168,21 +2168,20 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
}
// release spinlock & our lock; retry if reader-count changed
// (writer count cannot change since we hold lock)
- } while (!mu_.compare_exchange_weak(v, nv,
- std::memory_order_release,
+ } while (!mu_.compare_exchange_weak(v, nv, std::memory_order_release,
std::memory_order_relaxed));
break;
}
// There are waiters.
// Set h to the head of the circular waiter list.
- PerThreadSynch *h = GetPerThreadSynch(v);
+ PerThreadSynch* h = GetPerThreadSynch(v);
if ((v & kMuReader) != 0 && (h->readers & kMuHigh) > kMuOne) {
// a reader but not the last
- h->readers -= kMuOne; // release our lock
- intptr_t nv = v; // normally just release spinlock
+ h->readers -= kMuOne; // release our lock
+ intptr_t nv = v; // normally just release spinlock
if (waitp != nullptr) { // but waitp!=nullptr => must queue ourselves
- PerThreadSynch *new_h = Enqueue(h, waitp, v, kMuIsCond);
+ PerThreadSynch* new_h = Enqueue(h, waitp, v, kMuIsCond);
ABSL_RAW_CHECK(new_h != nullptr,
"waiters disappeared during Enqueue()!");
nv &= kMuLow;
@@ -2200,8 +2199,8 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
// The lock is becoming free, and there's a waiter
if (old_h != nullptr &&
- !old_h->may_skip) { // we used old_h as a terminator
- old_h->may_skip = true; // allow old_h to skip once more
+ !old_h->may_skip) { // we used old_h as a terminator
+ old_h->may_skip = true; // allow old_h to skip once more
ABSL_RAW_CHECK(old_h->skip == nullptr, "illegal skip from head");
if (h != old_h && MuEquivalentWaiter(old_h, old_h->next)) {
old_h->skip = old_h->next; // old_h not head & can skip to successor
@@ -2210,7 +2209,7 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
if (h->next->waitp->how == kExclusive &&
Condition::GuaranteedEqual(h->next->waitp->cond, nullptr)) {
// easy case: writer with no condition; no need to search
- pw = h; // wake w, the successor of h (=pw)
+ pw = h; // wake w, the successor of h (=pw)
w = h->next;
w->wake = true;
// We are waking up a writer. This writer may be racing against
@@ -2233,13 +2232,13 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
// waiter has a condition or is a reader. We avoid searching over
// waiters we've searched on previous iterations by starting at
// old_h if it's set. If old_h==h, there's no one to wakeup at all.
- if (old_h == h) { // we've searched before, and nothing's new
- // so there's no one to wake.
- intptr_t nv = (v & ~(kMuReader|kMuWriter|kMuWrWait));
+ if (old_h == h) { // we've searched before, and nothing's new
+ // so there's no one to wake.
+ intptr_t nv = (v & ~(kMuReader | kMuWriter | kMuWrWait));
h->readers = 0;
- h->maybe_unlocking = false; // finished unlocking
- if (waitp != nullptr) { // we must queue ourselves and sleep
- PerThreadSynch *new_h = Enqueue(h, waitp, v, kMuIsCond);
+ h->maybe_unlocking = false; // finished unlocking
+ if (waitp != nullptr) { // we must queue ourselves and sleep
+ PerThreadSynch* new_h = Enqueue(h, waitp, v, kMuIsCond);
nv &= kMuLow;
if (new_h != nullptr) {
nv |= kMuWait | reinterpret_cast<intptr_t>(new_h);
@@ -2253,12 +2252,12 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
}
// set up to walk the list
- PerThreadSynch *w_walk; // current waiter during list walk
- PerThreadSynch *pw_walk; // previous waiter during list walk
+ PerThreadSynch* w_walk; // current waiter during list walk
+ PerThreadSynch* pw_walk; // previous waiter during list walk
if (old_h != nullptr) { // we've searched up to old_h before
pw_walk = old_h;
w_walk = old_h->next;
- } else { // no prior search, start at beginning
+ } else { // no prior search, start at beginning
pw_walk =
nullptr; // h->next's predecessor may change; don't record it
w_walk = h->next;
@@ -2284,7 +2283,7 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
// to walk the path from w_walk to h inclusive. (TryRemove() can remove
// a waiter anywhere, but it acquires both the spinlock and the Mutex)
- old_h = h; // remember we searched to here
+ old_h = h; // remember we searched to here
// Walk the path upto and including h looking for waiters we can wake.
while (pw_walk != h) {
@@ -2296,24 +2295,24 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
// is in fact true
EvalConditionIgnored(this, w_walk->waitp->cond))) {
if (w == nullptr) {
- w_walk->wake = true; // can wake this waiter
+ w_walk->wake = true; // can wake this waiter
w = w_walk;
pw = pw_walk;
if (w_walk->waitp->how == kExclusive) {
wr_wait = kMuWrWait;
- break; // bail if waking this writer
+ break; // bail if waking this writer
}
} else if (w_walk->waitp->how == kShared) { // wake if a reader
w_walk->wake = true;
- } else { // writer with true condition
+ } else { // writer with true condition
wr_wait = kMuWrWait;
}
- } else { // can't wake; condition false
+ } else { // can't wake; condition false
known_false = w_walk->waitp->cond; // remember last false condition
}
- if (w_walk->wake) { // we're waking reader w_walk
- pw_walk = w_walk; // don't skip similar waiters
- } else { // not waking; skip as much as possible
+ if (w_walk->wake) { // we're waking reader w_walk
+ pw_walk = w_walk; // don't skip similar waiters
+ } else { // not waking; skip as much as possible
pw_walk = Skip(w_walk);
}
// If pw_walk == h, then load of pw_walk->next can race with
@@ -2340,8 +2339,8 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
h = DequeueAllWakeable(h, pw, &wake_list);
intptr_t nv = (v & kMuEvent) | kMuDesig;
- // assume no waiters left,
- // set kMuDesig for INV1a
+ // assume no waiters left,
+ // set kMuDesig for INV1a
if (waitp != nullptr) { // we must queue ourselves and sleep
h = Enqueue(h, waitp, v, kMuIsCond);
@@ -2354,7 +2353,7 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
if (h != nullptr) { // there are waiters left
h->readers = 0;
- h->maybe_unlocking = false; // finished unlocking
+ h->maybe_unlocking = false; // finished unlocking
nv |= wr_wait | kMuWait | reinterpret_cast<intptr_t>(h);
}
@@ -2365,12 +2364,12 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
}
// aggressive here; no one can proceed till we do
c = synchronization_internal::MutexDelay(c, AGGRESSIVE);
- } // end of for(;;)-loop
+ } // end of for(;;)-loop
if (wake_list != kPerThreadSynchNull) {
int64_t total_wait_cycles = 0;
int64_t max_wait_cycles = 0;
- int64_t now = base_internal::CycleClock::Now();
+ int64_t now = CycleClock::Now();
do {
// Profile lock contention events only if the waiter was trying to acquire
// the lock, not waiting on a condition variable or Condition.
@@ -2382,7 +2381,7 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
wake_list->waitp->contention_start_cycles = now;
wake_list->waitp->should_submit_contention_data = true;
}
- wake_list = Wakeup(wake_list); // wake waiters
+ wake_list = Wakeup(wake_list); // wake waiters
} while (wake_list != kPerThreadSynchNull);
if (total_wait_cycles > 0) {
mutex_tracer("slow release", this, total_wait_cycles);
@@ -2410,7 +2409,7 @@ void Mutex::Trans(MuHow how) {
// condition variable. If this mutex is free, we simply wake the thread.
// It will later acquire the mutex with high probability. Otherwise, we
// enqueue thread w on this mutex.
-void Mutex::Fer(PerThreadSynch *w) {
+void Mutex::Fer(PerThreadSynch* w) {
SchedulingGuard::ScopedDisable disable_rescheduling;
int c = 0;
ABSL_RAW_CHECK(w->waitp->cond == nullptr,
@@ -2435,9 +2434,9 @@ void Mutex::Fer(PerThreadSynch *w) {
IncrementSynchSem(this, w);
return;
} else {
- if ((v & (kMuSpin|kMuWait)) == 0) { // no waiters
+ if ((v & (kMuSpin | kMuWait)) == 0) { // no waiters
// This thread tries to become the one and only waiter.
- PerThreadSynch *new_h = Enqueue(nullptr, w->waitp, v, kMuIsCond);
+ PerThreadSynch* new_h = Enqueue(nullptr, w->waitp, v, kMuIsCond);
ABSL_RAW_CHECK(new_h != nullptr,
"Enqueue failed"); // we must queue ourselves
if (mu_.compare_exchange_strong(
@@ -2447,8 +2446,8 @@ void Mutex::Fer(PerThreadSynch *w) {
}
} else if ((v & kMuSpin) == 0 &&
mu_.compare_exchange_strong(v, v | kMuSpin | kMuWait)) {
- PerThreadSynch *h = GetPerThreadSynch(v);
- PerThreadSynch *new_h = Enqueue(h, w->waitp, v, kMuIsCond);
+ PerThreadSynch* h = GetPerThreadSynch(v);
+ PerThreadSynch* new_h = Enqueue(h, w->waitp, v, kMuIsCond);
ABSL_RAW_CHECK(new_h != nullptr,
"Enqueue failed"); // we must queue ourselves
do {
@@ -2467,19 +2466,18 @@ void Mutex::Fer(PerThreadSynch *w) {
void Mutex::AssertHeld() const {
if ((mu_.load(std::memory_order_relaxed) & kMuWriter) == 0) {
- SynchEvent *e = GetSynchEvent(this);
+ SynchEvent* e = GetSynchEvent(this);
ABSL_RAW_LOG(FATAL, "thread should hold write lock on Mutex %p %s",
- static_cast<const void *>(this),
- (e == nullptr ? "" : e->name));
+ static_cast<const void*>(this), (e == nullptr ? "" : e->name));
}
}
void Mutex::AssertReaderHeld() const {
if ((mu_.load(std::memory_order_relaxed) & (kMuReader | kMuWriter)) == 0) {
- SynchEvent *e = GetSynchEvent(this);
- ABSL_RAW_LOG(
- FATAL, "thread should hold at least a read lock on Mutex %p %s",
- static_cast<const void *>(this), (e == nullptr ? "" : e->name));
+ SynchEvent* e = GetSynchEvent(this);
+ ABSL_RAW_LOG(FATAL,
+ "thread should hold at least a read lock on Mutex %p %s",
+ static_cast<const void*>(this), (e == nullptr ? "" : e->name));
}
}
@@ -2490,13 +2488,17 @@ static const intptr_t kCvEvent = 0x0002L; // record events
static const intptr_t kCvLow = 0x0003L; // low order bits of CV
// Hack to make constant values available to gdb pretty printer
-enum { kGdbCvSpin = kCvSpin, kGdbCvEvent = kCvEvent, kGdbCvLow = kCvLow, };
+enum {
+ kGdbCvSpin = kCvSpin,
+ kGdbCvEvent = kCvEvent,
+ kGdbCvLow = kCvLow,
+};
static_assert(PerThreadSynch::kAlignment > kCvLow,
"PerThreadSynch::kAlignment must be greater than kCvLow");
-void CondVar::EnableDebugLog(const char *name) {
- SynchEvent *e = EnsureSynchEvent(&this->cv_, name, kCvEvent, kCvSpin);
+void CondVar::EnableDebugLog(const char* name) {
+ SynchEvent* e = EnsureSynchEvent(&this->cv_, name, kCvEvent, kCvSpin);
e->log = true;
UnrefSynchEvent(e);
}
@@ -2507,25 +2509,23 @@ CondVar::~CondVar() {
}
}
-
// Remove thread s from the list of waiters on this condition variable.
-void CondVar::Remove(PerThreadSynch *s) {
+void CondVar::Remove(PerThreadSynch* s) {
SchedulingGuard::ScopedDisable disable_rescheduling;
intptr_t v;
int c = 0;
for (v = cv_.load(std::memory_order_relaxed);;
v = cv_.load(std::memory_order_relaxed)) {
if ((v & kCvSpin) == 0 && // attempt to acquire spinlock
- cv_.compare_exchange_strong(v, v | kCvSpin,
- std::memory_order_acquire,
+ cv_.compare_exchange_strong(v, v | kCvSpin, std::memory_order_acquire,
std::memory_order_relaxed)) {
- PerThreadSynch *h = reinterpret_cast<PerThreadSynch *>(v & ~kCvLow);
+ PerThreadSynch* h = reinterpret_cast<PerThreadSynch*>(v & ~kCvLow);
if (h != nullptr) {
- PerThreadSynch *w = h;
+ PerThreadSynch* w = h;
while (w->next != s && w->next != h) { // search for thread
w = w->next;
}
- if (w->next == s) { // found thread; remove it
+ if (w->next == s) { // found thread; remove it
w->next = s->next;
if (h == s) {
h = (w == s) ? nullptr : w;
@@ -2534,7 +2534,7 @@ void CondVar::Remove(PerThreadSynch *s) {
s->state.store(PerThreadSynch::kAvailable, std::memory_order_release);
}
}
- // release spinlock
+ // release spinlock
cv_.store((v & kCvEvent) | reinterpret_cast<intptr_t>(h),
std::memory_order_release);
return;
@@ -2557,14 +2557,14 @@ void CondVar::Remove(PerThreadSynch *s) {
// variable queue just before the mutex is to be unlocked, and (most
// importantly) after any call to an external routine that might re-enter the
// mutex code.
-static void CondVarEnqueue(SynchWaitParams *waitp) {
+static void CondVarEnqueue(SynchWaitParams* waitp) {
// This thread might be transferred to the Mutex queue by Fer() when
// we are woken. To make sure that is what happens, Enqueue() doesn't
// call CondVarEnqueue() again but instead uses its normal code. We
// must do this before we queue ourselves so that cv_word will be null
// when seen by the dequeuer, who may wish immediately to requeue
// this thread on another queue.
- std::atomic<intptr_t> *cv_word = waitp->cv_word;
+ std::atomic<intptr_t>* cv_word = waitp->cv_word;
waitp->cv_word = nullptr;
intptr_t v = cv_word->load(std::memory_order_relaxed);
@@ -2577,8 +2577,8 @@ static void CondVarEnqueue(SynchWaitParams *waitp) {
v = cv_word->load(std::memory_order_relaxed);
}
ABSL_RAW_CHECK(waitp->thread->waitp == nullptr, "waiting when shouldn't be");
- waitp->thread->waitp = waitp; // prepare ourselves for waiting
- PerThreadSynch *h = reinterpret_cast<PerThreadSynch *>(v & ~kCvLow);
+ waitp->thread->waitp = waitp; // prepare ourselves for waiting
+ PerThreadSynch* h = reinterpret_cast<PerThreadSynch*>(v & ~kCvLow);
if (h == nullptr) { // add this thread to waiter list
waitp->thread->next = waitp->thread;
} else {
@@ -2591,8 +2591,8 @@ static void CondVarEnqueue(SynchWaitParams *waitp) {
std::memory_order_release);
}
-bool CondVar::WaitCommon(Mutex *mutex, KernelTimeout t) {
- bool rc = false; // return value; true iff we timed-out
+bool CondVar::WaitCommon(Mutex* mutex, KernelTimeout t) {
+ bool rc = false; // return value; true iff we timed-out
intptr_t mutex_v = mutex->mu_.load(std::memory_order_relaxed);
Mutex::MuHow mutex_how = ((mutex_v & kMuWriter) != 0) ? kExclusive : kShared;
@@ -2659,27 +2659,25 @@ bool CondVar::WaitCommon(Mutex *mutex, KernelTimeout t) {
return rc;
}
-bool CondVar::WaitWithTimeout(Mutex *mu, absl::Duration timeout) {
- return WaitWithDeadline(mu, DeadlineFromTimeout(timeout));
+bool CondVar::WaitWithTimeout(Mutex* mu, absl::Duration timeout) {
+ return WaitCommon(mu, KernelTimeout(timeout));
}
-bool CondVar::WaitWithDeadline(Mutex *mu, absl::Time deadline) {
+bool CondVar::WaitWithDeadline(Mutex* mu, absl::Time deadline) {
return WaitCommon(mu, KernelTimeout(deadline));
}
-void CondVar::Wait(Mutex *mu) {
- WaitCommon(mu, KernelTimeout::Never());
-}
+void CondVar::Wait(Mutex* mu) { WaitCommon(mu, KernelTimeout::Never()); }
// Wake thread w
// If it was a timed wait, w will be waiting on w->cv
// Otherwise, if it was not a Mutex mutex, w will be waiting on w->sem
// Otherwise, w is transferred to the Mutex mutex via Mutex::Fer().
-void CondVar::Wakeup(PerThreadSynch *w) {
+void CondVar::Wakeup(PerThreadSynch* w) {
if (w->waitp->timeout.has_timeout() || w->waitp->cvmu == nullptr) {
// The waiting thread only needs to observe "w->state == kAvailable" to be
// released, we must cache "cvmu" before clearing "next".
- Mutex *mu = w->waitp->cvmu;
+ Mutex* mu = w->waitp->cvmu;
w->next = nullptr;
w->state.store(PerThreadSynch::kAvailable, std::memory_order_release);
Mutex::IncrementSynchSem(mu, w);
@@ -2696,11 +2694,10 @@ void CondVar::Signal() {
for (v = cv_.load(std::memory_order_relaxed); v != 0;
v = cv_.load(std::memory_order_relaxed)) {
if ((v & kCvSpin) == 0 && // attempt to acquire spinlock
- cv_.compare_exchange_strong(v, v | kCvSpin,
- std::memory_order_acquire,
+ cv_.compare_exchange_strong(v, v | kCvSpin, std::memory_order_acquire,
std::memory_order_relaxed)) {
- PerThreadSynch *h = reinterpret_cast<PerThreadSynch *>(v & ~kCvLow);
- PerThreadSynch *w = nullptr;
+ PerThreadSynch* h = reinterpret_cast<PerThreadSynch*>(v & ~kCvLow);
+ PerThreadSynch* w = nullptr;
if (h != nullptr) { // remove first waiter
w = h->next;
if (w == h) {
@@ -2709,11 +2706,11 @@ void CondVar::Signal() {
h->next = w->next;
}
}
- // release spinlock
+ // release spinlock
cv_.store((v & kCvEvent) | reinterpret_cast<intptr_t>(h),
std::memory_order_release);
if (w != nullptr) {
- CondVar::Wakeup(w); // wake waiter, if there was one
+ CondVar::Wakeup(w); // wake waiter, if there was one
cond_var_tracer("Signal wakeup", this);
}
if ((v & kCvEvent) != 0) {
@@ -2728,7 +2725,7 @@ void CondVar::Signal() {
ABSL_TSAN_MUTEX_POST_SIGNAL(nullptr, 0);
}
-void CondVar::SignalAll () {
+void CondVar::SignalAll() {
ABSL_TSAN_MUTEX_PRE_SIGNAL(nullptr, 0);
intptr_t v;
int c = 0;
@@ -2742,11 +2739,11 @@ void CondVar::SignalAll () {
if ((v & kCvSpin) == 0 &&
cv_.compare_exchange_strong(v, v & kCvEvent, std::memory_order_acquire,
std::memory_order_relaxed)) {
- PerThreadSynch *h = reinterpret_cast<PerThreadSynch *>(v & ~kCvLow);
+ PerThreadSynch* h = reinterpret_cast<PerThreadSynch*>(v & ~kCvLow);
if (h != nullptr) {
- PerThreadSynch *w;
- PerThreadSynch *n = h->next;
- do { // for every thread, wake it up
+ PerThreadSynch* w;
+ PerThreadSynch* n = h->next;
+ do { // for every thread, wake it up
w = n;
n = n->next;
CondVar::Wakeup(w);
@@ -2774,42 +2771,41 @@ void ReleasableMutexLock::Release() {
}
#ifdef ABSL_HAVE_THREAD_SANITIZER
-extern "C" void __tsan_read1(void *addr);
+extern "C" void __tsan_read1(void* addr);
#else
#define __tsan_read1(addr) // do nothing if TSan not enabled
#endif
// A function that just returns its argument, dereferenced
-static bool Dereference(void *arg) {
+static bool Dereference(void* arg) {
// ThreadSanitizer does not instrument this file for memory accesses.
// This function dereferences a user variable that can participate
// in a data race, so we need to manually tell TSan about this memory access.
__tsan_read1(arg);
- return *(static_cast<bool *>(arg));
+ return *(static_cast<bool*>(arg));
}
ABSL_CONST_INIT const Condition Condition::kTrue;
-Condition::Condition(bool (*func)(void *), void *arg)
- : eval_(&CallVoidPtrFunction),
- arg_(arg) {
+Condition::Condition(bool (*func)(void*), void* arg)
+ : eval_(&CallVoidPtrFunction), arg_(arg) {
static_assert(sizeof(&func) <= sizeof(callback_),
"An overlarge function pointer passed to Condition.");
StoreCallback(func);
}
-bool Condition::CallVoidPtrFunction(const Condition *c) {
- using FunctionPointer = bool (*)(void *);
+bool Condition::CallVoidPtrFunction(const Condition* c) {
+ using FunctionPointer = bool (*)(void*);
FunctionPointer function_pointer;
std::memcpy(&function_pointer, c->callback_, sizeof(function_pointer));
return (*function_pointer)(c->arg_);
}
-Condition::Condition(const bool *cond)
+Condition::Condition(const bool* cond)
: eval_(CallVoidPtrFunction),
// const_cast is safe since Dereference does not modify arg
- arg_(const_cast<bool *>(cond)) {
- using FunctionPointer = bool (*)(void *);
+ arg_(const_cast<bool*>(cond)) {
+ using FunctionPointer = bool (*)(void*);
const FunctionPointer dereference = Dereference;
StoreCallback(dereference);
}
@@ -2819,7 +2815,7 @@ bool Condition::Eval() const {
return (this->eval_ == nullptr) || (*this->eval_)(this);
}
-bool Condition::GuaranteedEqual(const Condition *a, const Condition *b) {
+bool Condition::GuaranteedEqual(const Condition* a, const Condition* b) {
// kTrue logic.
if (a == nullptr || a->eval_ == nullptr) {
return b == nullptr || b->eval_ == nullptr;
generated by cgit v1.2.3 (git 2.39.1) at 2025-05-20 12:18:05 +0000