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af_unix: Revert 'lock_interruptible' in stream receive code 

With b3ca9b02b0, the AF_UNIX SOCK_STREAM
receive code was changed from using mutex_lock(&u->readlock) to
mutex_lock_interruptible(&u->readlock) to prevent signals from being
delayed for an indefinite time if a thread sleeping on the mutex
happened to be selected for handling the signal. But this was never a
problem with the stream receive code (as opposed to its datagram
counterpart) as that never went to sleep waiting for new messages with the
mutex held and thus, wouldn't cause secondary readers to block on the
mutex waiting for the sleeping primary reader. As the interruptible
locking makes the code more complicated in exchange for no benefit,
change it back to using mutex_lock.

Signed-off-by: Rainer Weikusat <rweikusat@mobileactivedefense.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Rainer Weikusat 2015-12-16 20:09:25 +00:00 committed by David S. Miller
parent 3036facbb7
commit 3822b5c2fc
1 changed files with 3 additions and 10 deletions
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13
net/unix/af_unix.c
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@ -2256,14 +2256,7 @@ static int unix_stream_read_generic(struct unix_stream_read_state *state)
/* Lock the socket to prevent queue disordering
* while sleeps in memcpy_tomsg
*/
err = mutex_lock_interruptible(&u->readlock);
if (unlikely(err)) {
/* recvmsg() in non blocking mode is supposed to return -EAGAIN
* sk_rcvtimeo is not honored by mutex_lock_interruptible()
*/
err = noblock ? -EAGAIN : -ERESTARTSYS;
goto out;
}
mutex_lock(&u->readlock);
if (flags & MSG_PEEK)
skip = sk_peek_offset(sk, flags);
@ -2307,12 +2300,12 @@ again:
timeo = unix_stream_data_wait(sk, timeo, last,
last_len);
if (signal_pending(current) ||
mutex_lock_interruptible(&u->readlock)) {
if (signal_pending(current)) {
err = sock_intr_errno(timeo);
goto out;
}
mutex_lock(&u->readlock);
continue;
unlock:
unix_state_unlock(sk);