Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755331AbXKPRY5 (ORCPT ); Fri, 16 Nov 2007 12:24:57 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755806AbXKPRYh (ORCPT ); Fri, 16 Nov 2007 12:24:37 -0500 Received: from x346.tv-sign.ru ([89.108.83.215]:57181 "EHLO mail.screens.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754642AbXKPRYg (ORCPT ); Fri, 16 Nov 2007 12:24:36 -0500 Date: Fri, 16 Nov 2007 20:24:13 +0300 From: Oleg Nesterov To: Andrew Morton Cc: Alexey Dobriyan , Kees Cook , Linus Torvalds , Roland McGrath , Scott James Remnant , linux-kernel@vger.kernel.org Subject: [PATCH 2/3] wait_task_stopped: tidy up the noreap case Message-ID: <20071116172413.GA7296@tv-sign.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1866 Lines: 49 wait_task_stopped(WNOWAIT) unlocks tasklist_lock and re-checks ->exit_code and ->exit_state. This is not needed: both were valid before we dropped the lock, and without tasklist_lock both are not stable anyway. Read the exit_code under tasklist and report the cached value without re-check. In fact this fixes the race with the dying child, we can report a completely false exit_code if ->exit_state is not visible yet. Signed-off-by: Oleg Nesterov --- 24/kernel/exit.c~2_NOREAP 2007-11-16 18:13:54.000000000 +0300 +++ 24/kernel/exit.c 2007-11-16 18:18:24.000000000 +0300 @@ -1356,10 +1356,10 @@ static int wait_task_stopped(struct task int noreap, struct siginfo __user *infop, int __user *stat_addr, struct rusage __user *ru) { - int retval, exit_code; + int retval, exit_code = p->exit_code; pid_t pid; - if (!p->exit_code) + if (!exit_code) return 0; if (delayed_group_leader && !(p->ptrace & PT_PTRACED) && p->signal->group_stop_count > 0) @@ -1384,9 +1384,6 @@ static int wait_task_stopped(struct task uid_t uid = p->uid; int why = (p->ptrace & PT_PTRACED) ? CLD_TRAPPED : CLD_STOPPED; - exit_code = p->exit_code; - if (unlikely(!exit_code) || unlikely(p->exit_state)) - goto bail_ref; return wait_noreap_copyout(p, pid, uid, why, (exit_code << 8) | 0x7f, infop, ru); @@ -1417,7 +1414,6 @@ static int wait_task_stopped(struct task * resumed, or it resumed and then died. */ write_unlock_irq(&tasklist_lock); -bail_ref: put_task_struct(p); /* * We are returning to the wait loop without having successfully - 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/