Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934032AbaDIRFm (ORCPT ); Wed, 9 Apr 2014 13:05:42 -0400 Received: from mx1.redhat.com ([209.132.183.28]:32701 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933353AbaDIRFj (ORCPT ); Wed, 9 Apr 2014 13:05:39 -0400 Date: Wed, 9 Apr 2014 19:05:42 +0200 From: Oleg Nesterov To: Steven Rostedt Cc: Mathieu Desnoyers , Frederic Weisbecker , LKML , Andrew Morton , Ingo Molnar Subject: [PATCH RESEND 1/2] tracing: syscall_*regfunc() can race with copy_process() Message-ID: <20140409170542.GB27638@redhat.com> References: <1397059882-23063-1-git-send-email-fweisbec@gmail.com> <1397059882-23063-3-git-send-email-fweisbec@gmail.com> <360091921.1294.1397060915052.JavaMail.zimbra@efficios.com> <20140409124249.4081e665@gandalf.local.home> <20140409170505.GA27638@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140409170505.GA27638@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 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 --- include/trace/syscall.h | 15 +++++++++++++++ kernel/fork.c | 2 ++ kernel/tracepoint.c | 12 +++++------- 3 files changed, 22 insertions(+), 7 deletions(-) diff --git a/include/trace/syscall.h b/include/trace/syscall.h index 84bc419..15a954b 100644 --- a/include/trace/syscall.h +++ b/include/trace/syscall.h @@ -4,6 +4,7 @@ #include #include #include +#include #include @@ -31,4 +32,18 @@ struct syscall_metadata { struct ftrace_event_call *exit_event; }; +#ifdef CONFIG_TRACEPOINTS +static inline void syscall_tracepoint_update(struct task_struct *p) +{ + if (test_thread_flag(TIF_SYSCALL_TRACEPOINT)) + set_tsk_thread_flag(p, TIF_SYSCALL_TRACEPOINT); + else + clear_tsk_thread_flag(p, TIF_SYSCALL_TRACEPOINT); +} +#else +static inline void syscall_tracepoint_update(struct task_struct *p) +{ +} +#endif + #endif /* _TRACE_SYSCALL_H */ diff --git a/kernel/fork.c b/kernel/fork.c index 1766d32..e463f99 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1472,7 +1472,9 @@ static struct task_struct *copy_process(unsigned long clone_flags, total_forks++; spin_unlock(¤t->sighand->siglock); + syscall_tracepoint_update(p); 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/