From patchwork Sun Oct 3 09:45:06 2010 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nagendra Tomar X-Patchwork-Id: 66595 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 96A5AB70CC for ; Sun, 3 Oct 2010 20:45:35 +1100 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752369Ab0JCJpI (ORCPT ); Sun, 3 Oct 2010 05:45:08 -0400 Received: from web53706.mail.re2.yahoo.com ([206.190.37.27]:43650 "HELO web53706.mail.re2.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751553Ab0JCJpH convert rfc822-to-8bit (ORCPT ); Sun, 3 Oct 2010 05:45:07 -0400 Received: (qmail 15970 invoked by uid 60001); 3 Oct 2010 09:45:06 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s1024; t=1286099106; bh=MHZDu+Uod2cSrQmwOjLsiJP3ZDk3Pjem2PRZ0/l3vmg=; h=Message-ID:X-YMail-OSG:Received:X-Mailer:Date:From:Subject:To:Cc:MIME-Version:Content-Type:Content-Transfer-Encoding; b=JFlCUPDfrTxes2U/G+nS8q12qXt3yG/FbX9W6t1IfGcGQ0avauVUTifjf6nThiE1cZTJbf32py0WvU0jJ6Y8mNWF1cY2+rOX/tqGTvDx2SWwC19vcRu+CCPVQCSkfYudGuBxp+bP3+FVzK2sVqAQx/XUSsEeO57LB6fRWYchmsg= DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=Message-ID:X-YMail-OSG:Received:X-Mailer:Date:From:Subject:To:Cc:MIME-Version:Content-Type:Content-Transfer-Encoding; b=OUyAGCeEYEqz+NsIt7iZotBAO0DZE8JbtWdTCaWqIvI6PBnSl7OH40LNenwLb/abL7XzlQxNGZGnnKWKCWUrWja5qVujvNUiqfwprjRvgVVXFVcHgF6dHYEy4WtMbctda0lXgexQ5yqAjrUpDVMYRM89yuACDhHRryXspO57ctQ=; Message-ID: <316201.7438.qm@web53706.mail.re2.yahoo.com> X-YMail-OSG: lllW8NQVM1lIsf.qvy.amezmvfCaAWDcQfQ7YjtfIPh5UI0 t9wP.hhB6Ex3MsmCPBObXw04FNNfQyG5QqLIzBLd0QnVl.Rm.fUVQN5DVXCB ZRuw4mbwJeSMp5hvlwm7VZnGTGlVLMk6UnT9lwHmTh3ho6chg3iaKsoXe9OE xstTC4w4e.iY8B5WdBTBcm0BaWB2uH7td4YeSY_m8R766k7pNQZ42d3jCyBF bbVT6.gVWbhpBxthevePIwq9CFhtCuhpceypw9LVHAlu7vK3aCz56J1LCqLR BfofvMz8i9X6EqltDPAQ2DUvk5rLxB_6r1nh3W4tdzh1K6H6_.ZB_WzF8V3W eipTABjE- Received: from [117.192.249.191] by web53706.mail.re2.yahoo.com via HTTP; Sun, 03 Oct 2010 02:45:06 PDT X-Mailer: YahooMailClassic/11.4.9 YahooMailWebService/0.8.105.279950 Date: Sun, 3 Oct 2010 02:45:06 -0700 (PDT) From: Nagendra Tomar Subject: [PATCH] net: Fix the condition passed to sk_wait_event() To: netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org, davem@davemloft.net MIME-Version: 1.0 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Resending, since this is the only patch now. Thanks. --- 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. Signed-off-by: Nagendra Singh Tomar --- --- -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html --- linux-2.6.35.7/net/core/stream.c.orig 2010-03-25 07:37:58.000000000 +0530 +++ linux-2.6.35.7/net/core/stream.c 2010-03-25 07:42:16.000000000 +0530 @@ -144,10 +144,10 @@ 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) {