diff options
| author | Pavel Begunkov <asml.silence@gmail.com> | 2025-04-03 12:29:30 +0100 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2025-04-03 08:31:57 -0600 |
| commit | 390513642ee6763c7ada07f0a1470474986e6c1c (patch) | |
| tree | b9ed41c998e188570d62ddfdced76327b56adba2 /io_uring | |
| parent | 57ed58c1325690ff6a46da776e9b42b14a7c37b1 (diff) | |
io_uring: always do atomic put from iowq
io_uring always switches requests to atomic refcounting for iowq
execution before there is any parallilism by setting REQ_F_REFCOUNT,
and the flag is not cleared until the request completes. That should be
fine as long as the compiler doesn't make up a non existing value for
the flags, however KCSAN still complains when the request owner changes
oter flag bits:
BUG: KCSAN: data-race in io_req_task_cancel / io_wq_free_work
...
read to 0xffff888117207448 of 8 bytes by task 3871 on cpu 0:
req_ref_put_and_test io_uring/refs.h:22 [inline]
Skip REQ_F_REFCOUNT checks for iowq, we know it's set.
Reported-by: syzbot+903a2ad71fb3f1e47cf5@syzkaller.appspotmail.com
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/d880bc27fb8c3209b54641be4ff6ac02b0e5789a.1743679736.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'io_uring')
| -rw-r--r-- | io_uring/io_uring.c | 2 | ||||
| -rw-r--r-- | io_uring/refs.h | 7 |
2 files changed, 8 insertions, 1 deletions
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index a4065e3d13d0..c6209fe44cb1 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -1796,7 +1796,7 @@ struct io_wq_work *io_wq_free_work(struct io_wq_work *work) struct io_kiocb *req = container_of(work, struct io_kiocb, work); struct io_kiocb *nxt = NULL; - if (req_ref_put_and_test(req)) { + if (req_ref_put_and_test_atomic(req)) { if (req->flags & IO_REQ_LINK_FLAGS) nxt = io_req_find_next(req); io_free_req(req); diff --git a/io_uring/refs.h b/io_uring/refs.h index 63982ead9f7d..0d928d87c4ed 100644 --- a/io_uring/refs.h +++ b/io_uring/refs.h @@ -17,6 +17,13 @@ static inline bool req_ref_inc_not_zero(struct io_kiocb *req) return atomic_inc_not_zero(&req->refs); } +static inline bool req_ref_put_and_test_atomic(struct io_kiocb *req) +{ + WARN_ON_ONCE(!(data_race(req->flags) & REQ_F_REFCOUNT)); + WARN_ON_ONCE(req_ref_zero_or_close_to_overflow(req)); + return atomic_dec_and_test(&req->refs); +} + static inline bool req_ref_put_and_test(struct io_kiocb *req) { if (likely(!(req->flags & REQ_F_REFCOUNT))) |