From 482964e56e1320cb7952faa1932d8ecf59c4bf75 Mon Sep 17 00:00:00 2001 From: Nagendra Tomar Date: Sat, 2 Oct 2010 23:45:06 +0000 Subject: [PATCH] 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: [] 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: [] 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 Signed-off-by: David S. Miller --- net/core/stream.c | 8 ++++---- 1 file 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, ¤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) { -- 2.39.5