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| author | Jens Axboe <axboe@fb.com> | 2014-09-16 10:37:37 -0600 |
|---|---|---|
| committer | Jens Axboe <axboe@fb.com> | 2014-09-22 11:54:04 -0600 |
| commit | 538b75341835e3c2041ff066408de10d24fdc830 (patch) | |
| tree | 6b7b60f296779302cc70d7c79e47b4dcc440a9be /block/blk-mq.c | |
| parent | 37504a3be90b69438426d74ccf467a9fe192932b (diff) | |
| download | lwn-538b75341835e3c2041ff066408de10d24fdc830.tar.gz lwn-538b75341835e3c2041ff066408de10d24fdc830.zip | |
blk-mq: request deadline must be visible before marking rq as started
When we start the request, we set the deadline and flip the bits
marking the request as started and non-complete. However, it's
important that the deadline store is ordered before flipping the
bits, otherwise we could have a small window where the request is
marked started but with an invalid deadline. This can confuse the
timeout handling.
Suggested-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block/blk-mq.c')
| -rw-r--r-- | block/blk-mq.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c index 383ea0cb1f0a..a13c40ca8230 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -393,6 +393,12 @@ static void blk_mq_start_request(struct request *rq, bool last) blk_add_timer(rq); /* + * Ensure that ->deadline is visible before set the started + * flag and clear the completed flag. + */ + smp_mb__before_atomic(); + + /* * Mark us as started and clear complete. Complete might have been * set if requeue raced with timeout, which then marked it as * complete. So be sure to clear complete again when we start |