smp: Fix more busy loops

We need to avoid the kernel optimizing away the reads from
memory. Use a standard relaxing instruction for that.

3 files changed, 9 insertions, 7 deletions

diff --git a/kern/eventcount.c b/kern/eventcount.c
index a9d7bd41..3a96b4fb 100644
--- a/kern/eventcount.c
+++ b/kern/eventcount.c
@@ -244,7 +244,7 @@ evc_signal(evc_t ev)
 #if (NCPUS > 1)
       retry:
 	while((thread->state & TH_RUN) || thread->lock.lock_data)
-		;
+		cpu_pause();
 #endif
 	thread_lock(thread);
 
diff --git a/kern/lock.c b/kern/lock.c
index a4b82522..81c6a129 100644
--- a/kern/lock.c
+++ b/kern/lock.c
@@ -36,6 +36,8 @@
 
 #include <string.h>
 
+#include <machine/smp.h>
+
 #include <kern/debug.h>
 #include <kern/lock.h>
 #include <kern/thread.h>
@@ -88,7 +90,7 @@ void simple_lock_init(simple_lock_t l)
 void simple_lock(simple_lock_t l)
 {
 	while (test_and_set((boolean_t *)l))
-		continue;
+		cpu_pause();
 }
 
 void simple_unlock(simple_lock_t l)
@@ -290,7 +292,7 @@ void lock_write(
 		if ((i = lock_wait_time) > 0) {
 			simple_unlock(&l->interlock);
 			while (--i > 0 && l->want_write)
-				continue;
+				cpu_pause();
 			simple_lock(&l->interlock);
 		}
 
@@ -310,7 +312,7 @@ void lock_write(
 			simple_unlock(&l->interlock);
 			while (--i > 0 && (l->read_count != 0 ||
 					l->want_upgrade))
-				continue;
+				cpu_pause();
 			simple_lock(&l->interlock);
 		}
 
@@ -384,7 +386,7 @@ void lock_read(
 		if ((i = lock_wait_time) > 0) {
 			simple_unlock(&l->interlock);
 			while (--i > 0 && (l->want_write || l->want_upgrade))
-				continue;
+				cpu_pause();
 			simple_lock(&l->interlock);
 		}
 
@@ -450,7 +452,7 @@ boolean_t lock_read_to_write(
 		if ((i = lock_wait_time) > 0) {
 			simple_unlock(&l->interlock);
 			while (--i > 0 && l->read_count != 0)
-				continue;
+				cpu_pause();
 			simple_lock(&l->interlock);
 		}
 
diff --git a/kern/machine.c b/kern/machine.c
index e8c9912e..bf9677c9 100644
--- a/kern/machine.c
+++ b/kern/machine.c
@@ -172,7 +172,7 @@ processor_request_action(
      *	state to running very soon.
      */
     while (*(volatile int *)&processor->state == PROCESSOR_DISPATCHING)
-    	continue;
+	cpu_pause();
 
     /*
      *	Now lock the action queue and do the dirty work.