From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966846AbaFTKr2 (ORCPT ); Fri, 20 Jun 2014 06:47:28 -0400 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.225]:51742 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S966748AbaFTKrN (ORCPT ); Fri, 20 Jun 2014 06:47:13 -0400 Message-Id: <20140620104711.567194570@goodmis.org> User-Agent: quilt/0.63-1 Date: Fri, 20 Jun 2014 06:45:21 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Oleg Nesterov Subject: [for-next][PATCH v2 3/3] tracing: syscall_regfunc() should not skip kernel threads References: <20140620104518.722157733@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline; filename=0003-tracing-syscall_regfunc-should-not-skip-kernel-threa.patch X-RR-Connecting-IP: 107.14.168.142:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Oleg Nesterov 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. Link: http://lkml.kernel.org/p/20140413185938.GD20668@redhat.com Signed-off-by: Oleg Nesterov Signed-off-by: Steven Rostedt --- kernel/tracepoint.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c index 9cf12640de5a..3490407dc7b7 100644 --- a/kernel/tracepoint.c +++ b/kernel/tracepoint.c @@ -497,9 +497,7 @@ 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); } -- 2.0.0