From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755521AbaDMS7j (ORCPT ); Sun, 13 Apr 2014 14:59:39 -0400 Received: from mx1.redhat.com ([209.132.183.28]:21510 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755470AbaDMS7g (ORCPT ); Sun, 13 Apr 2014 14:59:36 -0400 Date: Sun, 13 Apr 2014 20:59:38 +0200 From: Oleg Nesterov To: Steven Rostedt Cc: Mathieu Desnoyers , Frederic Weisbecker , LKML , Andrew Morton , Ingo Molnar Subject: [PATCH v2 3/3] tracing: syscall_regfunc() should not skip kernel threads Message-ID: <20140413185938.GD20668@redhat.com> References: <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> <20140409170542.GB27638@redhat.com> <20140410090643.46ca2226@gandalf.local.home> <20140410133435.GB12228@redhat.com> <20140411112259.79f0a0ba@gandalf.local.home> <20140411155845.GA30199@redhat.com> <20140413185828.GA20668@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140413185828.GA20668@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() ignores the kernel threads because "it has no effect", see cc3b13c1 "Don't trace kernel thread syscalls" which added this check. However, this means that a user-space task spawned by call_usermodehelper() will run without TIF_SYSCALL_TRACEPOINT if sys_tracepoint_refcount != 0. Remove this check. The unnecessary report from ret_from_fork path mentioned by cc3b13c1 is no longer possible, see See commit fb45550d76bb5 "make sure that kernel_thread() callbacks call do_exit() themselves". A kernel_thread() callback can only return and take the int_ret_from_sys_call path after do_execve() succeeds, otherwise the kernel will crash. But in this case it is no longer a kernel thread and thus is needs TIF_SYSCALL_TRACEPOINT. Signed-off-by: Oleg Nesterov --- kernel/tracepoint.c | 4 +--- 1 files changed, 1 insertions(+), 3 deletions(-) diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c index d907b7b..08456ba 100644 --- a/kernel/tracepoint.c +++ b/kernel/tracepoint.c @@ -747,9 +747,7 @@ void syscall_regfunc(void) if (!sys_tracepoint_refcount) { read_lock(&tasklist_lock); for_each_process_thread(p, t) { - /* Skip kernel threads. */ - if (!(t->flags & PF_KTHREAD)) - set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT); + set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT); } read_unlock(&tasklist_lock); } -- 1.5.5.1