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softirq: use bit waits instead of var waits.

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The waiting in softirq.c is always waiting for a bit to be cleared.
This makes the bit wait functions seem more suitable.
By switching over we can rid of all explicit barriers.  We also use
wait_on_bit_lock() to avoid an explicit loop.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240925053405.3960701-8-neilb@suse.de
This commit is contained in:
NeilBrown 2024-09-25 15:31:44 +10:00 committed by Peter Zijlstra
parent 80681c04c5
commit 49994911b4
1 changed files with 4 additions and 10 deletions
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14
kernel/softirq.c
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@ -748,10 +748,8 @@ EXPORT_SYMBOL(__tasklet_hi_schedule);
static bool tasklet_clear_sched(struct tasklet_struct *t)
{
if (test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) {
wake_up_var(&t->state);
if (test_and_clear_wake_up_bit(TASKLET_STATE_SCHED, &t->state))
return true;
}
WARN_ONCE(1, "tasklet SCHED state not set: %s %pS\n",
t->use_callback ? "callback" : "func",
@ -871,8 +869,7 @@ void tasklet_kill(struct tasklet_struct *t)
if (in_interrupt())
pr_notice("Attempt to kill tasklet from interrupt\n");
while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state))
wait_var_event(&t->state, !test_bit(TASKLET_STATE_SCHED, &t->state));
wait_on_bit_lock(&t->state, TASKLET_STATE_SCHED, TASK_UNINTERRUPTIBLE);
tasklet_unlock_wait(t);
tasklet_clear_sched(t);
@ -882,16 +879,13 @@ EXPORT_SYMBOL(tasklet_kill);
#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
void tasklet_unlock(struct tasklet_struct *t)
{
smp_mb__before_atomic();
clear_bit(TASKLET_STATE_RUN, &t->state);
smp_mb__after_atomic();
wake_up_var(&t->state);
clear_and_wake_up_bit(TASKLET_STATE_RUN, &t->state);
}
EXPORT_SYMBOL_GPL(tasklet_unlock);
void tasklet_unlock_wait(struct tasklet_struct *t)
{
wait_var_event(&t->state, !test_bit(TASKLET_STATE_RUN, &t->state));
wait_on_bit(&t->state, TASKLET_STATE_RUN, TASK_UNINTERRUPTIBLE);
}
EXPORT_SYMBOL_GPL(tasklet_unlock_wait);
#endif