[lkml]   [2019]   [Dec]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH] 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 <>
Signed-off-by: Jan Stancek <>
fs/pipe.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

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 @@ static inline bool pipe_writable(const struct pipe_inode_info *pipe)
wait_event_interruptible(pipe->wait, pipe_writable(pipe));
- was_empty = pipe_empty(head, pipe->tail);
+ was_empty = pipe_empty(pipe->head, pipe->tail);
 \ /
  Last update: 2019-12-22 13:36    [W:0.022 / U:6.252 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site