tree 71f2a601e325fd5724e05b685675e7c7b749ebcf
parent a28c8b9db8a1014aa572cd19a3bdb9ddebd3e555
author Linus Torvalds <torvalds@linux-foundation.org> 1575755589 -0800
committer Linus Torvalds <torvalds@linux-foundation.org> 1575755589 -0800

pipe: don't use 'pipe_wait() for basic pipe IO

pipe_wait() may be simple, but since it relies on the pipe lock, it
means that we have to do the wakeup while holding the lock.  That's
unfortunate, because the very first thing the waked entity will want to
do is to get the pipe lock for itself.

So get rid of the pipe_wait() usage by simply releasing the pipe lock,
doing the wakeup (if required) and then using wait_event_interruptible()
to wait on the right condition instead.

wait_event_interruptible() handles races on its own by comparing the
wakeup condition before and after adding itself to the wait queue, so
you can use an optimistic unlocked condition for it.

Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>