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Commit 863fddcb authored by Jens Axboe's avatar Jens Axboe
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as-iosched: properly protect ioc_gone and ioc count 



If we have multiple tasks freeing io contexts when as-iosched
is being unloaded, we could complete() ioc_gone twice. Fix that by
protecting ioc_gone complete() and clearing with a spinlock for
just that purpose. Doesn't matter from a performance perspective,
since it'll only enter that path when ioc_gone != NULL (when as-iosched
is being rmmod'ed).

Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 9a11b4ed

block/as-iosched.c

+15 −3
Original line number Diff line number Diff line
@@ -151,6 +151,7 @@ enum arq_state { 


static DEFINE_PER_CPU(unsigned long, ioc_count);

static struct completion *ioc_gone;

static DEFINE_SPINLOCK(ioc_gone_lock);



static void as_move_to_dispatch(struct as_data *ad, struct request *rq);

static void as_antic_stop(struct as_data *ad);
@@ -164,8 +165,19 @@ static void free_as_io_context(struct as_io_context *aic) 
{

	kfree(aic);

	elv_ioc_count_dec(ioc_count);

	if (ioc_gone && !elv_ioc_count_read(ioc_count))

	if (ioc_gone) {

		/*

		 * AS scheduler is exiting, grab exit lock and check

		 * the pending io context count. If it hits zero,

		 * complete ioc_gone and set it back to NULL.

		 */

		spin_lock(&ioc_gone_lock);

		if (ioc_gone && !elv_ioc_count_read(ioc_count)) {

			complete(ioc_gone);

			ioc_gone = NULL;

		}

		spin_unlock(&ioc_gone_lock);

	}

}



static void as_trim(struct io_context *ioc)
@@ -1493,7 +1505,7 @@ static void __exit as_exit(void) 
	/* ioc_gone's update must be visible before reading ioc_count */

	smp_wmb();

	if (elv_ioc_count_read(ioc_count))

		wait_for_completion(ioc_gone);

		wait_for_completion(&all_gone);

	synchronize_rcu();

}