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[4.2.y-ckt,stable] Patch "af_unix: Revert 'lock_interruptible' in stream receive code" has been added to staging queue

Message ID 1452020492-20267-1-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa Jan. 5, 2016, 7:01 p.m. UTC 
This is a note to let you know that I have just added a patch titled

    af_unix: Revert 'lock_interruptible' in stream receive code

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt1.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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From 7232429c3a9e192708f3950ebd8eb9327493b80b Mon Sep 17 00:00:00 2001
From: Rainer Weikusat <rweikusat@mobileactivedefense.com>
Date: Wed, 16 Dec 2015 20:09:25 +0000
Subject: af_unix: Revert 'lock_interruptible' in stream receive code

[ Upstream commit 3822b5c2fc62e3de8a0f33806ff279fb7df92432 ]

With b3ca9b02b00704053a38bfe4c31dbbb9c13595d0, 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: Kamal Mostafa <kamal@canonical.com>
---
 net/unix/af_unix.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

--
1.9.1
diff mbox

Patch

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 128b098..0fc6dba 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -2255,14 +2255,7 @@  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);
@@ -2306,12 +2299,12 @@  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);