diff options
| author | Jan Stancek <jstancek@redhat.com> | 2019-12-22 13:33:24 +0100 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-12-22 09:47:47 -0800 |
| commit | 0dd1e3773ae8afc4bfdce782bdeffc10f9cae6ec (patch) | |
| tree | 65b6d77c5be91eb0104945af6598bf8d9718426e /fs | |
| parent | b8e382a185ebb1bca66bd541e5a0f858b6b9cbb9 (diff) | |
pipe: fix empty pipe check in pipe_write()
LTP pipeio_1 test is hanging with v5.5-rc2-385-gb8e382a185eb,
with read side observing empty pipe and sleeping and write
side running out of space and then sleeping as well. In this
scenario there are 5 writers and 1 reader.
Problem is that after pipe_write() reacquires pipe lock, it
re-checks for empty pipe with potentially stale 'head' and
doesn't wake up read side anymore. pipe->tail can advance
beyond 'head', because there are multiple writers.
Use pipe->head for empty pipe check after reacquiring lock
to observe current state.
Testing: With patch, LTP pipeio_1 ran successfully in loop for 1 hour.
Without patch it hanged within a minute.
Fixes: 1b6b26ae7053 ("pipe: fix and clarify pipe write wakeup logic")
Reported-by: Rachel Sibley <rasibley@redhat.com>
Signed-off-by: Jan Stancek <jstancek@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/pipe.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/pipe.c b/fs/pipe.c index 04d004ee2e8c..57502c3c0fba 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -581,7 +581,7 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from) } wait_event_interruptible(pipe->wait, pipe_writable(pipe)); __pipe_lock(pipe); - was_empty = pipe_empty(head, pipe->tail); + was_empty = pipe_empty(pipe->head, pipe->tail); } out: __pipe_unlock(pipe); |