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authorAlexander Gordeev <agordeev@redhat.com>2014-06-17 22:37:23 +0200
committerJens Axboe <axboe@fb.com>2014-06-17 22:13:08 -0700
commit86fb5c56cfa26de5e91c9a50e2767a695dff366e (patch)
treeda76443281fb15c54d56400b25ff9279e0b9e33e /block/blk-mq-tag.c
parent2971c35f35886b87af54675313a2afef937c1b0c (diff)
downloadkernel-86fb5c56cfa26de5e91c9a50e2767a695dff366e.tar.gz
blk-mq: bitmap tag: fix races in bt_get() function
This update fixes few issues in bt_get() function: - list_empty(&wait.task_list) check is not protected; - was_empty check is always true which results in *every* thread entering the loop resets bt_wait_state::wait_cnt counter rather than every bt->wake_cnt'th thread; - 'bt_wait_state::wait_cnt' counter update is redundant, since it also gets reset in bt_clear_tag() function; Cc: Christoph Hellwig <hch@infradead.org> Cc: Ming Lei <tom.leiming@gmail.com> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Alexander Gordeev <agordeev@redhat.com> Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block/blk-mq-tag.c')
-rw-r--r--block/blk-mq-tag.c13
1 files changed, 5 insertions, 8 deletions
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 08fc6716d362..c1b92426c95e 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -248,18 +248,12 @@ static int bt_get(struct blk_mq_alloc_data *data,
bs = bt_wait_ptr(bt, hctx);
do {
- bool was_empty;
-
- was_empty = list_empty(&wait.task_list);
prepare_to_wait(&bs->wait, &wait, TASK_UNINTERRUPTIBLE);
tag = __bt_get(hctx, bt, last_tag);
if (tag != -1)
break;
- if (was_empty)
- atomic_set(&bs->wait_cnt, bt->wake_cnt);
-
blk_mq_put_ctx(data->ctx);
io_schedule();
@@ -519,10 +513,13 @@ static int bt_alloc(struct blk_mq_bitmap_tags *bt, unsigned int depth,
return -ENOMEM;
}
- for (i = 0; i < BT_WAIT_QUEUES; i++)
+ bt_update_count(bt, depth);
+
+ for (i = 0; i < BT_WAIT_QUEUES; i++) {
init_waitqueue_head(&bt->bs[i].wait);
+ atomic_set(&bt->bs[i].wait_cnt, bt->wake_cnt);
+ }
- bt_update_count(bt, depth);
return 0;
}