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af_unix: Revert 'lock_interruptible' in stream receive code

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[ Upstream commit 3822b5c2fc ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Rainer Weikusat
2015-12-16 20:09:25 +00:00
committed by Greg Kroah-Hartman
parent 2bc1b5b3a6
commit cc01a0aa28
1 changed files with 3 additions and 10 deletions
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13
net/unix/af_unix.c
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@@ -2072,14 +2072,7 @@ static int unix_stream_recvmsg(struct socket *sock, struct msghdr *msg,
memset(&scm, 0, sizeof(scm));
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);
@@ -2120,12 +2113,12 @@ again:
timeo = unix_stream_data_wait(sk, timeo, last);
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);