From: Jens Axboe Date: Thu, 29 May 2008 07:32:08 +0000 (+0200) Subject: cfq-iosched: properly protect ioc_gone and ioc count X-Git-Tag: v2.6.27-rc1~1114^2~36 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9a11b4ed0e7c44bca7c939aa544c3c47aae40c12;p=linux-2.6 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: Jens Axboe --- diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index d01b411c72..32aa3674f8 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -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)) - complete(ioc_gone); + 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(); }