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authorNagendra Tomar <tomer_iisc@yahoo.com>2010-10-02 23:45:06 +0000
committerDavid S. Miller <davem@davemloft.net>2010-10-03 20:41:32 -0700
commit482964e56e1320cb7952faa1932d8ecf59c4bf75 (patch)
treeacd265499553bb1d26d2939e891a92f6d9079cb4 /net
parentae878ae280bea286ff2b1e1cb6e609dd8cb4501d (diff)
net: Fix the condition passed to sk_wait_event()
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 <tomer_iisc@yahoo.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/core/stream.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/net/core/stream.c b/net/core/stream.c
index d959e0f41528..f5df85dcd20b 100644
--- a/net/core/stream.c
+++ b/net/core/stream.c
@@ -141,10 +141,10 @@ int sk_stream_wait_memory(struct sock *sk, long *timeo_p)
set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
sk->sk_write_pending++;
- sk_wait_event(sk, &current_timeo, !sk->sk_err &&
- !(sk->sk_shutdown & SEND_SHUTDOWN) &&
- sk_stream_memory_free(sk) &&
- vm_wait);
+ sk_wait_event(sk, &current_timeo, sk->sk_err ||
+ (sk->sk_shutdown & SEND_SHUTDOWN) ||
+ (sk_stream_memory_free(sk) &&
+ !vm_wait));
sk->sk_write_pending--;
if (vm_wait) {

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