Commit 49994911 authored by NeilBrown's avatar NeilBrown Committed by Peter Zijlstra
Browse files

softirq: use bit waits instead of var waits. 



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: default avatarNeilBrown <neilb@suse.de>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240925053405.3960701-8-neilb@suse.de
parent 80681c04

kernel/softirq.c

+4 −10
Original line number Diff line number Diff line
@@ -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