Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757485AbXE1J7Y (ORCPT ); Mon, 28 May 2007 05:59:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751099AbXE1J7Q (ORCPT ); Mon, 28 May 2007 05:59:16 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:33892 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750810AbXE1J7P (ORCPT ); Mon, 28 May 2007 05:59:15 -0400 Date: Mon, 28 May 2007 18:58:50 +0900 Message-ID: <87fy5hb76t.wl%takeuchi_satoru@jp.fujitsu.com> From: Satoru Takeuchi To: Oleg Nesterov Cc: Satoru Takeuchi , Alan Cox , Andrew Morton , "Eric W. Biederman" , Ingo Molnar , Roland McGrath , linux-kernel@vger.kernel.org Subject: Re: [BUG] signal: multithread program returns with wrong errno on receiving SIGSTOP In-Reply-To: <20070528070753.GA989@tv-sign.ru> References: <20070528070753.GA989@tv-sign.ru> User-Agent: Wanderlust/2.14.0 (Africa) SEMI/1.14.6 (Maruoka) FLIM/1.14.8 (=?ISO-8859-4?Q?Shij=F2?=) APEL/10.6 Emacs/21.4 (i486-pc-linux-gnu) MULE/5.0 (SAKAKI) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2672 Lines: 89 Hi Oleg, At Mon, 28 May 2007 11:07:53 +0400, Oleg Nesterov wrote: > > Satoru Takeuchi wrote: > > > > I found a bug on signal subsystem. If there is some multithread program > > and one of the thread is blocking on the system call, it returns with > > wrong errno on receiving SIGSTOP and following SIGCONT. > > It doesn't matter in this particular case, but in general it is good to > report the kernel version as well. > > > 1. issue the test program (attached on this mail) from term A. > > > > $ ./mt-wrong-errno > > > > 2. send SIGSTOP to test program from term B. > > > > $ ps a > > ... > > 9685 pts/3 Sl+ 0:00 ./mt-wrong-errno > > 9688 pts/4 R+ 0:00 ps a > > $ kill -STOP 9685 > > > > 3. send SIGCONT to test program from term B. > > > > $ kill -CONT 9685 > > > > Expected Result > > =============== > > > > `./mt-wrong-errno' restarts read syscall (and stop again by receiving > > SIGTTIN). > > > > Actual Result > > ============= > > > > `./mt-wrong-errno' returns with wrong errno 512 means ERESTARTSYS. > > The comment on include/linux/errno.h says "this errno should never be > > seen by user program." So it's definitely a bug. > > Wild guess, > > drivers/char/n_tty.c:job_control() > > kill_pgrp(task_pgrp(current), SIGTTIN, 1); > return -ERESTARTSYS; > > This is wrong. kill_pgrp()->__group_send_sig_info() sends SIGTTIN > to the thread group, but can choose any sub-thread as a target for > signal_wake_up(). > > This means we return ERESTARTSYS, but signal_pending() != true, bug. > > Satoru, could you re-test with the untested patch below? I tested this patch on my ia64 box and it works fine. # Since I don't know anything about tty driver, I can't determine its # adequacy immediately, sorry. Satoru > > Oleg. > > --- t/drivers/char/n_tty.c~ 2007-04-05 12:18:26.000000000 +0400 > +++ t/drivers/char/n_tty.c 2007-05-28 10:57:58.000000000 +0400 > @@ -1191,6 +1191,7 @@ static int job_control(struct tty_struct > is_current_pgrp_orphaned()) > return -EIO; > kill_pgrp(task_pgrp(current), SIGTTIN, 1); > + set_thread_flag(TIF_SIGPENDING); > return -ERESTARTSYS; > } > } > > - > 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/ - 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/