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authorOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>2006-04-18 09:44:06 +0200
committerJens Axboe <axboe@suse.de>2006-04-18 09:44:06 +0200
commitfba822722e3f9d438fca8fd9541d7ddd447d7a48 (patch)
tree05fc35428f61fb6b66726e3aae03ce9187212c21 /block
parenta9a5cd5d2a57fb76dbae2115450f777b69beccf7 (diff)
downloadlinux-linaro-stable-fba822722e3f9d438fca8fd9541d7ddd447d7a48.tar.gz
[PATCH 1/2] iosched: fix typo and barrier()
On rmmod path, cfq/as waits to make sure all io-contexts was freed. However, it's using complete(), not wait_for_completion(). I think barrier() is not enough in here. To avoid the following case, this patch replaces barrier() with smb_wmb(). cpu0 visibility cpu1 [ioc_gnone=NULL,ioc_count=1] ioc_gnone = &all_gone NULL,ioc_count=1 atomic_read(&ioc_count) NULL,ioc_count=1 wait_for_completion() NULL,ioc_count=0 atomic_sub_and_test() NULL,ioc_count=0 if ( && ioc_gone) [ioc_gone==NULL, so doesn't call complete()] &all_gone,ioc_count=0 Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> Signed-off-by: Jens Axboe <axboe@suse.de>
Diffstat (limited to 'block')
-rw-r--r--block/as-iosched.c5
-rw-r--r--block/cfq-iosched.c5
2 files changed, 6 insertions, 4 deletions
diff --git a/block/as-iosched.c b/block/as-iosched.c
index 296708ceceb2..e25a5d79ab27 100644
--- a/block/as-iosched.c
+++ b/block/as-iosched.c
@@ -1844,9 +1844,10 @@ static void __exit as_exit(void)
DECLARE_COMPLETION(all_gone);
elv_unregister(&iosched_as);
ioc_gone = &all_gone;
- barrier();
+ /* ioc_gone's update must be visible before reading ioc_count */
+ smp_wmb();
if (atomic_read(&ioc_count))
- complete(ioc_gone);
+ wait_for_completion(ioc_gone);
synchronize_rcu();
kmem_cache_destroy(arq_pool);
}
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 67d446de0227..01820b1094e9 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -2439,9 +2439,10 @@ static void __exit cfq_exit(void)
DECLARE_COMPLETION(all_gone);
elv_unregister(&iosched_cfq);
ioc_gone = &all_gone;
- barrier();
+ /* ioc_gone's update must be visible before reading ioc_count */
+ smp_wmb();
if (atomic_read(&ioc_count))
- complete(ioc_gone);
+ wait_for_completion(ioc_gone);
synchronize_rcu();
cfq_slab_kill();
}