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Move preemption handling out of critical_exit.

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In preperataion for making the enter/exit pair inline.

Reviewed by:	kib
This commit is contained in:
Mateusz Guzik 2018-05-22 19:24:57 +00:00
parent defd918d79
commit 748b15fc02
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=334062
1 changed files with 36 additions and 35 deletions
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71
sys/kern/kern_switch.c
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@ -209,48 +209,49 @@ critical_enter(void)
(long)td->td_proc->p_pid, td->td_name, td->td_critnest);
}
void
critical_exit(void)
static void __noinline
critical_exit_preempt(void)
{
struct thread *td;
int flags;
td = curthread;
KASSERT(td->td_owepreempt != 0,
("critical_exit: td_owepreempt == 0"));
if (td->td_critnest != 0)
return;
if (kdb_active)
return;
/*
* Microoptimization: we committed to switch,
* disable preemption in interrupt handlers
* while spinning for the thread lock.
*/
td->td_critnest = 1;
thread_lock(td);
td->td_critnest--;
flags = SW_INVOL | SW_PREEMPT;
if (TD_IS_IDLETHREAD(td))
flags |= SWT_IDLE;
else
flags |= SWT_OWEPREEMPT;
mi_switch(flags, NULL);
thread_unlock(td);
}
void
critical_exit(void)
{
struct thread *td;
td = curthread;
KASSERT(td->td_critnest != 0,
("critical_exit: td_critnest == 0"));
if (td->td_critnest == 1) {
td->td_critnest = 0;
/*
* Interrupt handlers execute critical_exit() on
* leave, and td_owepreempt may be left set by an
* interrupt handler only when td_critnest > 0. If we
* are decrementing td_critnest from 1 to 0, read
* td_owepreempt after decrementing, to not miss the
* preempt. Disallow compiler to reorder operations.
*/
__compiler_membar();
if (td->td_owepreempt && !kdb_active) {
/*
* Microoptimization: we committed to switch,
* disable preemption in interrupt handlers
* while spinning for the thread lock.
*/
td->td_critnest = 1;
thread_lock(td);
td->td_critnest--;
flags = SW_INVOL | SW_PREEMPT;
if (TD_IS_IDLETHREAD(td))
flags |= SWT_IDLE;
else
flags |= SWT_OWEPREEMPT;
mi_switch(flags, NULL);
thread_unlock(td);
}
} else
td->td_critnest--;
td->td_critnest--;
__compiler_membar();
if (__predict_false(td->td_owepreempt))
critical_exit_preempt();
CTR4(KTR_CRITICAL, "critical_exit by thread %p (%ld, %s) to %d", td,
(long)td->td_proc->p_pid, td->td_name, td->td_critnest);
}