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Replace spin lock with the set of atomics. It is impractical for one

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tc_ticktock() call to wait for another's completion -- just skip it.
This commit is contained in:
Alexander Motin 2010-09-14 04:57:30 +00:00
parent dd9595e7fa
commit 4763a8b8c1
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=212601
1 changed files with 14 additions and 10 deletions
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24
sys/kern/kern_clock.c
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@ -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();