Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754668AbYCCNVW (ORCPT ); Mon, 3 Mar 2008 08:21:22 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751814AbYCCNVO (ORCPT ); Mon, 3 Mar 2008 08:21:14 -0500 Received: from x346.tv-sign.ru ([89.108.83.215]:43926 "EHLO mail.screens.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750915AbYCCNVN (ORCPT ); Mon, 3 Mar 2008 08:21:13 -0500 Date: Mon, 3 Mar 2008 16:25:02 +0300 From: Oleg Nesterov To: Roland McGrath Cc: Jiri Kosina , Davide Libenzi , Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [PATCH] [RFC] fix missed SIGCONT cases Message-ID: <20080303132502.GA81@tv-sign.ru> References: <20080227210038.93AFC2700FD@magilla.localdomain> <20080228102649.071572700FD@magilla.localdomain> <20080228153043.GA11484@tv-sign.ru> <20080229023902.D93E12700FD@magilla.localdomain> <20080229120101.GA1410@tv-sign.ru> <20080301015956.A0D262700FE@magilla.localdomain> <20080301164102.GA171@tv-sign.ru> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="ZPt4rx8FFjLCG7dd" Content-Disposition: inline In-Reply-To: <20080301164102.GA171@tv-sign.ru> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6581 Lines: 188 --ZPt4rx8FFjLCG7dd Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Actually, it is easy to re-use signal_struct->flags from the very beginning, no need to introduce the new flag temporary, see the attached patches. I also have a couple of simple cleanups on top of them (use cached ->signal value). Perhaps, we can add the new helper which sets SIGNAL_GROUP_EXIT but preserves SIGNAL_CLD_MASK, but I don't think this is really needed. Oleg. --ZPt4rx8FFjLCG7dd Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="1_SIGCONT_IMPL.patch" --- 25/include/linux/sched.h~1_SIGCONT_IMPL 2008-02-17 23:40:09.000000000 +0300 +++ 25/include/linux/sched.h 2008-03-03 13:40:14.000000000 +0300 @@ -555,6 +555,12 @@ struct signal_struct { #define SIGNAL_STOP_DEQUEUED 0x00000002 /* stop signal dequeued */ #define SIGNAL_STOP_CONTINUED 0x00000004 /* SIGCONT since WCONTINUED reap */ #define SIGNAL_GROUP_EXIT 0x00000008 /* group exit in progress */ +/* + * Pending notifications to parent. + */ +#define SIGNAL_CLD_STOPPED 0x00000010 +#define SIGNAL_CLD_CONTINUED 0x00000020 +#define SIGNAL_CLD_MASK (SIGNAL_CLD_STOPPED|SIGNAL_CLD_CONTINUED) /* If true, all threads except ->group_exit_task have pending SIGKILL */ static inline int signal_group_exit(const struct signal_struct *sig) --- 25/kernel/signal.c~1_SIGCONT_IMPL 2008-02-17 23:40:09.000000000 +0300 +++ 25/kernel/signal.c 2008-03-03 13:51:55.000000000 +0300 @@ -595,10 +595,8 @@ static void handle_stop_signal(int sig, * the SIGCHLD was pending on entry to this kill. */ p->signal->group_stop_count = 0; - p->signal->flags = SIGNAL_STOP_CONTINUED; - spin_unlock(&p->sighand->siglock); - do_notify_parent_cldstop(p, CLD_STOPPED); - spin_lock(&p->sighand->siglock); + p->signal->flags = SIGNAL_STOP_CONTINUED | + SIGNAL_CLD_STOPPED; } rm_from_queue(SIG_KERNEL_STOP_MASK, &p->signal->shared_pending); t = p; @@ -635,25 +633,23 @@ static void handle_stop_signal(int sig, * We were in fact stopped, and are now continued. * Notify the parent with CLD_CONTINUED. */ - p->signal->flags = SIGNAL_STOP_CONTINUED; + p->signal->flags = SIGNAL_STOP_CONTINUED | + SIGNAL_CLD_CONTINUED; p->signal->group_exit_code = 0; - spin_unlock(&p->sighand->siglock); - do_notify_parent_cldstop(p, CLD_CONTINUED); - spin_lock(&p->sighand->siglock); } else { /* * We are not stopped, but there could be a stop * signal in the middle of being processed after * being removed from the queue. Clear that too. */ - p->signal->flags = 0; + p->signal->flags &= ~SIGNAL_STOP_DEQUEUED; } } else if (sig == SIGKILL) { /* * Make sure that any pending stop signal already dequeued * is undone by the wakeup for SIGKILL. */ - p->signal->flags = 0; + p->signal->flags &= ~SIGNAL_STOP_DEQUEUED; } } @@ -1761,6 +1757,19 @@ int get_signal_to_deliver(siginfo_t *inf relock: spin_lock_irq(¤t->sighand->siglock); + + if (unlikely(current->signal->flags & SIGNAL_CLD_MASK)) { + int why = (current->signal->flags & SIGNAL_STOP_CONTINUED) + ? CLD_CONTINUED : CLD_STOPPED; + current->signal->flags &= ~SIGNAL_CLD_MASK; + spin_unlock_irq(¤t->sighand->siglock); + + read_lock(&tasklist_lock); + do_notify_parent_cldstop(current->group_leader, why); + read_unlock(&tasklist_lock); + goto relock; + } + for (;;) { struct k_sigaction *ka; --ZPt4rx8FFjLCG7dd Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="2_HSS_SIMPLIFY.patch" --- 25/kernel/signal.c~2_HSS_SIMPLIFY 2008-03-03 13:51:55.000000000 +0300 +++ 25/kernel/signal.c 2008-03-03 14:47:39.000000000 +0300 @@ -577,33 +577,16 @@ static void handle_stop_signal(int sig, t = next_thread(t); } while (t != p); } else if (sig == SIGCONT) { + unsigned int why; /* * Remove all stop signals from all queues, * and wake all threads. */ - if (unlikely(p->signal->group_stop_count > 0)) { - /* - * There was a group stop in progress. We'll - * pretend it finished before we got here. We are - * obliged to report it to the parent: if the - * SIGSTOP happened "after" this SIGCONT, then it - * would have cleared this pending SIGCONT. If it - * happened "before" this SIGCONT, then the parent - * got the SIGCHLD about the stop finishing before - * the continue happened. We do the notification - * now, and it's as if the stop had finished and - * the SIGCHLD was pending on entry to this kill. - */ - p->signal->group_stop_count = 0; - p->signal->flags = SIGNAL_STOP_CONTINUED | - SIGNAL_CLD_STOPPED; - } rm_from_queue(SIG_KERNEL_STOP_MASK, &p->signal->shared_pending); t = p; do { unsigned int state; rm_from_queue(SIG_KERNEL_STOP_MASK, &t->pending); - /* * If there is a handler for SIGCONT, we must make * sure that no thread returns to user mode before @@ -613,7 +596,7 @@ static void handle_stop_signal(int sig, * running the handler. With the TIF_SIGPENDING * flag set, the thread will pause and acquire the * siglock that we hold now and until we've queued - * the pending signal. + * the pending signal. * * Wake up the stopped thread _after_ setting * TIF_SIGPENDING @@ -628,13 +611,23 @@ static void handle_stop_signal(int sig, t = next_thread(t); } while (t != p); - if (p->signal->flags & SIGNAL_STOP_STOPPED) { - /* - * We were in fact stopped, and are now continued. - * Notify the parent with CLD_CONTINUED. - */ - p->signal->flags = SIGNAL_STOP_CONTINUED | - SIGNAL_CLD_CONTINUED; + /* + * Notify the parent with CLD_CONTINUED if we were stopped. + * + * If we were in the middle of a group stop, we pretend it + * was already finished, and then continued. Since SIGCHLD + * doesn't queue we report only CLD_STOPPED, as if the next + * CLD_CONTINUED was dropped. + */ + why = 0; + if (p->signal->flags & SIGNAL_STOP_STOPPED) + why |= SIGNAL_CLD_CONTINUED; + else if (p->signal->group_stop_count) + why |= SIGNAL_CLD_STOPPED; + + if (why) { + p->signal->flags = why | SIGNAL_STOP_CONTINUED; + p->signal->group_stop_count = 0; p->signal->group_exit_code = 0; } else { /* --ZPt4rx8FFjLCG7dd-- -- 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/