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Jan Stancek authored
LTP pipeio_1 test is hanging with v5.5-rc2-385-gb8e382a1, 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: 1b6b26ae ("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>
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