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| author | Guoju Fang <fangguoju@gmail.com> | 2019-11-13 16:03:16 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-10-01 11:11:51 +0200 |
| commit | 20b4b82b02a427b598492de2fcf366d30c9933fc (patch) | |
| tree | d2b1d9eed87ff887f7a57f1423f4b921c206dbd4 /drivers | |
| parent | f8e23211976f2ecaf4ab86052ec98b88e2cac5eb (diff) | |
bcache: fix a lost wake-up problem caused by mca_cannibalize_lock
[ Upstream commit 34cf78bf34d48dddddfeeadb44f9841d7864997a ]
This patch fix a lost wake-up problem caused by the race between
mca_cannibalize_lock and bch_cannibalize_unlock.
Consider two processes, A and B. Process A is executing
mca_cannibalize_lock, while process B takes c->btree_cache_alloc_lock
and is executing bch_cannibalize_unlock. The problem happens that after
process A executes cmpxchg and will execute prepare_to_wait. In this
timeslice process B executes wake_up, but after that process A executes
prepare_to_wait and set the state to TASK_INTERRUPTIBLE. Then process A
goes to sleep but no one will wake up it. This problem may cause bcache
device to dead.
Signed-off-by: Guoju Fang <fangguoju@gmail.com>
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/md/bcache/bcache.h | 1 | ||||
| -rw-r--r-- | drivers/md/bcache/btree.c | 12 | ||||
| -rw-r--r-- | drivers/md/bcache/super.c | 1 |
3 files changed, 10 insertions, 4 deletions
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h index 7fe7df56fa33..f0939fc1cfe5 100644 --- a/drivers/md/bcache/bcache.h +++ b/drivers/md/bcache/bcache.h @@ -547,6 +547,7 @@ struct cache_set { */ wait_queue_head_t btree_cache_wait; struct task_struct *btree_cache_alloc_lock; + spinlock_t btree_cannibalize_lock; /* * When we free a btree node, we increment the gen of the bucket the diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c index 122d97522094..bdf6071c1b18 100644 --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -841,15 +841,17 @@ out: static int mca_cannibalize_lock(struct cache_set *c, struct btree_op *op) { - struct task_struct *old; - - old = cmpxchg(&c->btree_cache_alloc_lock, NULL, current); - if (old && old != current) { + spin_lock(&c->btree_cannibalize_lock); + if (likely(c->btree_cache_alloc_lock == NULL)) { + c->btree_cache_alloc_lock = current; + } else if (c->btree_cache_alloc_lock != current) { if (op) prepare_to_wait(&c->btree_cache_wait, &op->wait, TASK_UNINTERRUPTIBLE); + spin_unlock(&c->btree_cannibalize_lock); return -EINTR; } + spin_unlock(&c->btree_cannibalize_lock); return 0; } @@ -884,10 +886,12 @@ static struct btree *mca_cannibalize(struct cache_set *c, struct btree_op *op, */ static void bch_cannibalize_unlock(struct cache_set *c) { + spin_lock(&c->btree_cannibalize_lock); if (c->btree_cache_alloc_lock == current) { c->btree_cache_alloc_lock = NULL; wake_up(&c->btree_cache_wait); } + spin_unlock(&c->btree_cannibalize_lock); } static struct btree *mca_alloc(struct cache_set *c, struct btree_op *op, diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c index f7f8fb079d2a..d73f9ea77686 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -1511,6 +1511,7 @@ struct cache_set *bch_cache_set_alloc(struct cache_sb *sb) sema_init(&c->sb_write_mutex, 1); mutex_init(&c->bucket_lock); init_waitqueue_head(&c->btree_cache_wait); + spin_lock_init(&c->btree_cannibalize_lock); init_waitqueue_head(&c->bucket_wait); init_waitqueue_head(&c->gc_wait); sema_init(&c->uuid_write_mutex, 1); |