From 863fddcb4b0caee4c2d5bd6e3b28779920516db3 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Thu, 29 May 2008 09:35:22 +0200 Subject: [PATCH] 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: Jens Axboe --- block/as-iosched.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/block/as-iosched.c b/block/as-iosched.c index 743f33a01a07..9735acb5b4f5 100644 --- a/block/as-iosched.c +++ b/block/as-iosched.c @@ -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)) - complete(ioc_gone); + 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(); } -- 2.20.1