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Commit 9a11b4ed authored by Jens Axboe's avatar Jens Axboe
Browse files

cfq-iosched: properly protect ioc_gone and ioc count 



If we have multiple tasks freeing cfq_io_contexts when cfq-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 cfq-iosched
is being rmmod'ed).

Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent c461a973

block/cfq-iosched.c

+15 −3
Original line number Diff line number Diff line
@@ -48,6 +48,7 @@ static struct kmem_cache *cfq_ioc_pool; 


static DEFINE_PER_CPU(unsigned long, ioc_count);

static struct completion *ioc_gone;

static DEFINE_SPINLOCK(ioc_gone_lock);



#define CFQ_PRIO_LISTS		IOPRIO_BE_NR

#define cfq_class_idle(cfqq)	((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
@@ -1177,8 +1178,19 @@ static void cfq_cic_free_rcu(struct rcu_head *head) 
	kmem_cache_free(cfq_ioc_pool, cic);

	elv_ioc_count_dec(ioc_count);



	if (ioc_gone && !elv_ioc_count_read(ioc_count))

	if (ioc_gone) {

		/*

		 * CFQ 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 cfq_cic_free(struct cfq_io_context *cic)
@@ -2317,7 +2329,7 @@ static void __exit cfq_exit(void) 
	 * pending RCU callbacks

	 */

	if (elv_ioc_count_read(ioc_count))

		wait_for_completion(ioc_gone);

		wait_for_completion(&all_gone);

	cfq_slab_kill();

}