Synchronization: Support true relative timeouts using the POSIX

proposed standard pthread_cond_clockwait() and sem_clockwait().
These are currently implemented in glibc >= 2.30.

These methods take a clock and use an absolute time with reference
to that clock, so KernelTimeout now can produce these values.

PiperOrigin-RevId: 522824226
Change-Id: Ife98713f6f95d800b1f8e52d5364a3dbebc4f8a6

1 files changed, 10 insertions, 0 deletions

diff --git a/absl/synchronization/internal/pthread_waiter.cc b/absl/synchronization/internal/pthread_waiter.cc
index a8dafd94..8d90cc45 100644
--- a/absl/synchronization/internal/pthread_waiter.cc
+++ b/absl/synchronization/internal/pthread_waiter.cc
@@ -78,6 +78,11 @@ PthreadWaiter::PthreadWaiter() : waiter_count_(0), wakeup_count_(0) {
 #define ABSL_INTERNAL_HAS_PTHREAD_COND_TIMEDWAIT_RELATIVE_NP 1
 #endif
 
+#if defined(__GLIBC__) && \
+    (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 30))
+#define ABSL_INTERNAL_HAVE_PTHREAD_COND_CLOCKWAIT 1
+#endif
+
 // Calls pthread_cond_timedwait() or possibly something else like
 // pthread_cond_timedwait_relative_np() depending on the platform and
 // KernelTimeout requested. The return value is the same as the return
@@ -94,6 +99,11 @@ int PthreadWaiter::TimedWait(KernelTimeout t) {
 #ifdef ABSL_INTERNAL_HAS_PTHREAD_COND_TIMEDWAIT_RELATIVE_NP
     const auto rel_timeout = t.MakeRelativeTimespec();
     return pthread_cond_timedwait_relative_np(&cv_, &mu_, &rel_timeout);
+#elif defined(ABSL_INTERNAL_HAVE_PTHREAD_COND_CLOCKWAIT) && \
+    defined(CLOCK_MONOTONIC)
+    const auto abs_clock_timeout = t.MakeClockAbsoluteTimespec(CLOCK_MONOTONIC);
+    return pthread_cond_clockwait(&cv_, &mu_, CLOCK_MONOTONIC,
+                                  &abs_clock_timeout);
 #endif
   }