Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756614Ab3CQSaj (ORCPT ); Sun, 17 Mar 2013 14:30:39 -0400 Received: from mx1.redhat.com ([209.132.183.28]:8019 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756429Ab3CQSag (ORCPT ); Sun, 17 Mar 2013 14:30:36 -0400 Date: Sun, 17 Mar 2013 19:28:32 +0100 From: Oleg Nesterov To: Andrew Morton , Ingo Molnar Cc: Frederic Weisbecker , Steven Rostedt , linux-kernel@vger.kernel.org Subject: [PATCH 1/2] tracing: syscall_*regfunc() can race with copy_process() Message-ID: <20130317182831.GA22986@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130317182814.GA22968@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2777 Lines: 95 syscall_regfunc() and syscall_unregfunc() should set/clear TIF_SYSCALL_TRACEPOINT system-wide, but do_each_thread() can race with copy_process() and miss the new child which was not added to init_task.tasks list yet. Change copy_process() to update the child's TIF_SYSCALL_TRACEPOINT under tasklist. While at it, - remove _irqsafe from syscall_regfunc/syscall_unregfunc, read_lock(tasklist) doesn't need to disable irqs. - change syscall_unregfunc() to check PF_KTHREAD to skip the kernel threads, ->mm != NULL is the common mistake. Note: probably this check should be simply removed, needs another patch. Signed-off-by: Oleg Nesterov --- kernel/fork.c | 7 +++++++ kernel/tracepoint.c | 12 +++++------- 2 files changed, 12 insertions(+), 7 deletions(-) diff --git a/kernel/fork.c b/kernel/fork.c index 1766d32..8184a53 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1472,7 +1472,14 @@ static struct task_struct *copy_process(unsigned long clone_flags, total_forks++; spin_unlock(¤t->sighand->siglock); +#ifdef CONFIG_TRACEPOINTS + if (test_thread_flag(TIF_SYSCALL_TRACEPOINT)) + set_tsk_thread_flag(p, TIF_SYSCALL_TRACEPOINT); + else + clear_tsk_thread_flag(p, TIF_SYSCALL_TRACEPOINT); +#endif write_unlock_irq(&tasklist_lock); + proc_fork_connector(p); cgroup_post_fork(p); if (clone_flags & CLONE_THREAD) diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c index 0c05a45..a16754b 100644 --- a/kernel/tracepoint.c +++ b/kernel/tracepoint.c @@ -732,33 +732,31 @@ static int sys_tracepoint_refcount; void syscall_regfunc(void) { - unsigned long flags; struct task_struct *g, *t; if (!sys_tracepoint_refcount) { - read_lock_irqsave(&tasklist_lock, flags); + read_lock(&tasklist_lock); do_each_thread(g, t) { /* Skip kernel threads. */ - if (t->mm) + if (!(t->flags & PF_KTHREAD)) set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT); } while_each_thread(g, t); - read_unlock_irqrestore(&tasklist_lock, flags); + read_unlock(&tasklist_lock); } sys_tracepoint_refcount++; } void syscall_unregfunc(void) { - unsigned long flags; struct task_struct *g, *t; sys_tracepoint_refcount--; if (!sys_tracepoint_refcount) { - read_lock_irqsave(&tasklist_lock, flags); + read_lock(&tasklist_lock); do_each_thread(g, t) { clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT); } while_each_thread(g, t); - read_unlock_irqrestore(&tasklist_lock, flags); + read_unlock(&tasklist_lock); } } #endif -- 1.5.5.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/