Author: mav
Date: Tue Sep 14 04:57:30 2010
New Revision: 212601
URL: http://svn.freebsd.org/changeset/base/212601
Log:
Replace spin lock with the set of atomics. It is impractical for one
tc_ticktock() call to wait for another's completion -- just skip it.
Modified:
head/sys/kern/kern_clock.c
Modified: head/sys/kern/kern_clock.c
==============================================================================
--- head/sys/kern/kern_clock.c Tue Sep 14 04:48:04 2010 (r212600)
+++ head/sys/kern/kern_clock.c Tue Sep 14 04:57:30 2010 (r212601)
@@ -374,8 +374,7 @@ int ticks;
int psratio;
static DPCPU_DEFINE(int, pcputicks); /* Per-CPU version of ticks. */
-static struct mtx global_hardclock_mtx;
-MTX_SYSINIT(global_hardclock_mtx, &global_hardclock_mtx, "ghc_mtx", MTX_SPIN);
+static int global_hardclock_run = 0;
/*
* Initialize clock frequencies and start both clocks running.
@@ -485,8 +484,10 @@ hardclock_anycpu(int cnt, int usermode)
struct thread *td = curthread;
struct proc *p = td->td_proc;
int *t = DPCPU_PTR(pcputicks);
- int flags;
- int global, newticks;
+ int flags, global, newticks;
+#ifdef SW_WATCHDOG
+ int i;
+#endif /* SW_WATCHDOG */
/*
* Update per-CPU and possibly global ticks values.
@@ -535,19 +536,22 @@ hardclock_anycpu(int cnt, int usermode)
callout_tick();
/* We are in charge to handle this tick duty. */
if (newticks > 0) {
- mtx_lock_spin(&global_hardclock_mtx);
- tc_ticktock();
+ /* Dangerous and no need to call these things concurrently. */
+ if (atomic_cmpset_acq_int(&global_hardclock_run, 0, 1)) {
+ tc_ticktock();
#ifdef DEVICE_POLLING
- hardclock_device_poll(); /* This is very short and quick. */
+ /* This is very short and quick. */
+ hardclock_device_poll();
#endif /* DEVICE_POLLING */
+ atomic_store_rel_int(&global_hardclock_run, 0);
+ }
#ifdef SW_WATCHDOG
if (watchdog_enabled > 0) {
- watchdog_ticks -= newticks;
- if (watchdog_ticks <= 0)
+ i = atomic_fetchadd_int(&watchdog_ticks, -newticks);
+ if (i > 0 && i <= newticks)
watchdog_fire();
}
#endif /* SW_WATCHDOG */
- mtx_unlock_spin(&global_hardclock_mtx);
}
if (curcpu == CPU_FIRST())
cpu_tick_calibration();
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