From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753354Ab1GZLfq (ORCPT ); Tue, 26 Jul 2011 07:35:46 -0400 Received: from mga02.intel.com ([134.134.136.20]:36282 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752130Ab1GZLfk (ORCPT ); Tue, 26 Jul 2011 07:35:40 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.67,268,1309762800"; d="scan'208";a="32070219" From: Mika Westerberg To: linux-kernel@vger.kernel.org Cc: Mika Westerberg , Peter Zijlstra , Ingo Molnar Subject: [PATCH RESEND] sched: fix false lockdep warning in set_task_cpu() Date: Tue, 26 Jul 2011 14:36:01 +0300 Message-Id: <1311680161-23755-1-git-send-email-mika.westerberg@linux.intel.com> X-Mailer: git-send-email 1.7.5.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When we have CONFIG_LOCKDEP enabled we get occasionally following warning on the system console at boot: WARNING: at kernel/sched.c:2204 set_task_cpu+0x1a1/0x390() Modules linked in: Pid: 133, comm: mount Not tainted 3.0.0-rc2+ #70 Call Trace: [] warn_slowpath_common+0x6d/0xa0 [] ? set_task_cpu+0x1a1/0x390 [] ? set_task_cpu+0x1a1/0x390 [] warn_slowpath_null+0x1d/0x20 [] set_task_cpu+0x1a1/0x390 [] try_to_wake_up+0x127/0x250 [] default_wake_function+0xb/0x10 [] autoremove_wake_function+0x1e/0x50 [] __wake_up_common+0x40/0x70 [] __wake_up+0x37/0x50 [] ? serial_m3110_enable_ms+0x10/0x10 [] serial_m3110_con_write+0x55/0x60 [] __call_console_drivers+0x75/0x90 [] _call_console_drivers+0x49/0x80 [] console_unlock+0xca/0x1f0 [] vprintk+0x18f/0x4f0 [] ? trace_hardirqs_on+0xb/0x10 [] ? lockdep_init_map+0x4e/0x4c0 [] ? trace_hardirqs_on+0xb/0x10 [] printk+0x18/0x1a [] ext3_msg+0x3e/0x40 [] ext3_fill_super+0x16ba/0x1960 [] ? disk_name+0x88/0xc0 [] mount_bdev+0x16d/0x1b0 [] ? __kmalloc_track_caller+0xf7/0x280 [] ? alloc_vfsmnt+0x81/0x140 [] ext3_mount+0x1a/0x20 [] ? ext3_clear_journal_err+0xa0/0xa0 [] mount_fs+0x1c/0xc0 [] ? __alloc_percpu+0xa/0x10 [] ? alloc_vfsmnt+0x9b/0x140 [] vfs_kern_mount+0x46/0xa0 [] do_kern_mount+0x39/0xd0 [] do_mount+0x2c7/0x680 [] ? strndup_user+0x49/0x60 [] sys_mount+0x66/0xa0 [] sysenter_do_call+0x12/0x36 This is due the fact that printk() disables lockdep before the output is passed to the actual console driver. If the console driver happens to call some functions which eventually calls set_task_cpu() we end up failing the following test: WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) || lockdep_is_held(&task_rq(p)->lock))); This is because lockdep_is_held() returns 0 if lockdep is temporarily disabled. So we check whether lockdep is enabled and only then validate the locks. Signed-off-by: Mika Westerberg Cc: Peter Zijlstra Cc: Ingo Molnar --- kernel/sched.c | 5 +++-- 1 files changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/sched.c b/kernel/sched.c index 9769c75..1177f81 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -2211,8 +2211,9 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu) * Furthermore, all task_rq users should acquire both locks, see * task_rq_lock(). */ - WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) || - lockdep_is_held(&task_rq(p)->lock))); + WARN_ON_ONCE(debug_locks && !current->lockdep_recursion && + !(lockdep_is_held(&p->pi_lock) || + lockdep_is_held(&task_rq(p)->lock))); #endif #endif -- 1.7.5.4