This is a note to let you know that I've just added the patch titled
net: Fix the condition passed to sk_wait_event()
to the 2.6.27-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-fix-the-condition-passed-to-sk_wait_event.patch
and it can be found in the queue-2.6.27 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From bcd127108a3ea649bac24527a48e2217a921e801 Mon Sep 17 00:00:00 2001
From: Nagendra Tomar <[email protected]>
Date: Sat, 2 Oct 2010 23:45:06 +0000
Subject: net: Fix the condition passed to sk_wait_event()
From: Nagendra Tomar <[email protected]>
[ Upstream commit 482964e56e1320cb7952faa1932d8ecf59c4bf75 ]
This patch fixes the condition (3rd arg) passed to sk_wait_event() in
sk_stream_wait_memory(). The incorrect check in sk_stream_wait_memory()
causes the following soft lockup in tcp_sendmsg() when the global tcp
memory pool has exhausted.
>>> snip <<<
localhost kernel: BUG: soft lockup - CPU#3 stuck for 11s! [sshd:6429]
localhost kernel: CPU 3:
localhost kernel: RIP: 0010:[sk_stream_wait_memory+0xcd/0x200]
[sk_stream_wait_memory+0xcd/0x200] sk_stream_wait_memory+0xcd/0x200
localhost kernel:
localhost kernel: Call Trace:
localhost kernel: [sk_stream_wait_memory+0x1b1/0x200]
sk_stream_wait_memory+0x1b1/0x200
localhost kernel: [<ffffffff802557c0>] autoremove_wake_function+0x0/0x40
localhost kernel: [ipv6:tcp_sendmsg+0x6e6/0xe90] tcp_sendmsg+0x6e6/0xce0
localhost kernel: [sock_aio_write+0x126/0x140] sock_aio_write+0x126/0x140
localhost kernel: [xfs:do_sync_write+0xf1/0x130] do_sync_write+0xf1/0x130
localhost kernel: [<ffffffff802557c0>] autoremove_wake_function+0x0/0x40
localhost kernel: [hrtimer_start+0xe3/0x170] hrtimer_start+0xe3/0x170
localhost kernel: [vfs_write+0x185/0x190] vfs_write+0x185/0x190
localhost kernel: [sys_write+0x50/0x90] sys_write+0x50/0x90
localhost kernel: [system_call+0x7e/0x83] system_call+0x7e/0x83
>>> snip <<<
What is happening is, that the sk_wait_event() condition passed from
sk_stream_wait_memory() evaluates to true for the case of tcp global memory
exhaustion. This is because both sk_stream_memory_free() and vm_wait are true
which causes sk_wait_event() to *not* call schedule_timeout().
Hence sk_stream_wait_memory() returns immediately to the caller w/o sleeping.
This causes the caller to again try allocation, which again fails and again
calls sk_stream_wait_memory(), and so on.
[ Bug introduced by commit c1cbe4b7ad0bc4b1d98ea708a3fecb7362aa4088
("[NET]: Avoid atomic xchg() for non-error case") -DaveM ]
Signed-off-by: Nagendra Singh Tomar <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
net/core/stream.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
--- a/net/core/stream.c
+++ b/net/core/stream.c
@@ -139,10 +139,10 @@ int sk_stream_wait_memory(struct sock *s
set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
sk->sk_write_pending++;
- sk_wait_event(sk, ¤t_timeo, !sk->sk_err &&
- !(sk->sk_shutdown &
SEND_SHUTDOWN) &&
- sk_stream_memory_free(sk) &&
- vm_wait);
+ sk_wait_event(sk, ¤t_timeo, sk->sk_err ||
+ (sk->sk_shutdown &
SEND_SHUTDOWN) ||
+ (sk_stream_memory_free(sk) &&
+ !vm_wait));
sk->sk_write_pending--;
if (vm_wait) {
Patches currently in stable-queue which might be from [email protected] are
queue-2.6.27/net-fix-the-condition-passed-to-sk_wait_event.patch
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