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| author |   Guoju Fang <fangguoju@gmail.com> | 2019-11-13 16:03:16 +0800 |
|---|---|---|
| committer |   Jens Axboe <axboe@kernel.dk> | 2019-11-13 15:42:50 -0700 |
| commit | 34cf78bf34d48dddddfeeadb44f9841d7864997a (patch) | |
| tree | d6010b3ea9defa5300f679f4fe8bd55d85ebd2bd /drivers/md/bcache/btree.c | |
| parent | bcache: fix fifo index swapping condition in journal_pin_cmp() (diff) | |
| download | linux-dev-34cf78bf34d48dddddfeeadb44f9841d7864997a.tar.xz linux-dev-34cf78bf34d48dddddfeeadb44f9841d7864997a.zip | |
bcache: fix a lost wake-up problem caused by mca_cannibalize_lock
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>
Diffstat (limited to 'drivers/md/bcache/btree.c')
| -rw-r--r-- | drivers/md/bcache/btree.c | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c index 00523cd1db80..39d7fc1ef1ee 100644 --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -910,15 +910,17 @@ 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; } @@ -953,10 +955,12 @@ 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, |