Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755673Ab1E2XNM (ORCPT ); Sun, 29 May 2011 19:13:12 -0400 Received: from mail-bw0-f46.google.com ([209.85.214.46]:56170 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754241Ab1E2XNB (ORCPT ); Sun, 29 May 2011 19:13:01 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:from:to:cc:subject:date:message-id:x-mailer:in-reply-to :references; b=Qim72s21sKfM9nZ9t+0pX7fnotgjBDpgPjPnHuGJAtg1iJ5Ya79MSKpJuVa2NdRrH7 bmsLwlx92iPXq9/+QkRkQbY5/JQZKnZrqxGVmIdFX11RSiYh0mTnBq/IYK3uIDM8LzA+ XwZitsVbILbYbvDe0ntjvuIVn1w+HdEGd4adk= From: Tejun Heo To: oleg@redhat.com Cc: vda.linux@googlemail.com, jan.kratochvil@redhat.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, indan@nul.nu, bdonlan@gmail.com, pedro@codesourcery.com, Tejun Heo Subject: [PATCH 07/17] job control: introduce task_set_jobctl_pending() Date: Mon, 30 May 2011 01:12:30 +0200 Message-Id: <1306710760-16440-8-git-send-email-tj@kernel.org> X-Mailer: git-send-email 1.7.5.2 In-Reply-To: <1306710760-16440-1-git-send-email-tj@kernel.org> References: <1306710760-16440-1-git-send-email-tj@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4745 Lines: 140 task->jobctl currently hosts JOBCTL_STOP_PENDING and will host TRAP pending bits too. Setting pending conditions on a dying task may make the task unkillable. Currently, each setting site is responsible for checking for the condition but with to-be-added job control traps this becomes too fragile. This patch adds task_set_jobctl_pending() which should be used when setting task->jobctl bits to schedule a stop or trap. The function performs the followings to ease setting pending bits. * Sanity checks. * If fatal signal is pending or PF_EXITING is set, no bit is set. * STOP_SIGMASK is automatically cleared if new value is being set. do_signal_stop() and ptrace_attach() are updated to use task_set_jobctl_pending() instead of setting STOP_PENDING explicitly. The surrounding structures around setting are changed to fit task_set_jobctl_pending() better but there should be no userland visible behavior difference. Signed-off-by: Tejun Heo Cc: Oleg Nesterov --- include/linux/sched.h | 2 ++ kernel/ptrace.c | 6 +++--- kernel/signal.c | 46 ++++++++++++++++++++++++++++++++++++++++------ 3 files changed, 45 insertions(+), 9 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 11791dd..bc7a380 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1819,6 +1819,8 @@ extern void thread_group_times(struct task_struct *p, cputime_t *ut, cputime_t * #define JOBCTL_PENDING_MASK JOBCTL_STOP_PENDING +extern bool task_set_jobctl_pending(struct task_struct *task, + unsigned int mask); extern void task_clear_jobctl_pending(struct task_struct *task, unsigned int mask); diff --git a/kernel/ptrace.c b/kernel/ptrace.c index cbda3c2..1506556 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -256,10 +256,10 @@ static int ptrace_attach(struct task_struct *task) * The following task_is_stopped() test is safe as both transitions * in and out of STOPPED are protected by siglock. */ - if (task_is_stopped(task)) { - task->jobctl |= JOBCTL_STOP_PENDING | JOBCTL_TRAPPING; + if (task_is_stopped(task) && + task_set_jobctl_pending(task, + JOBCTL_STOP_PENDING | JOBCTL_TRAPPING)) signal_wake_up(task, 1); - } spin_unlock(&task->sighand->siglock); diff --git a/kernel/signal.c b/kernel/signal.c index 637a171..9ab91c5 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -224,6 +224,39 @@ static inline void print_dropped_signal(int sig) } /** + * task_set_jobctl_pending - set jobctl pending bits + * @task: target task + * @mask: pending bits to set + * + * Clear @mask from @task->jobctl. @mask must be subset of + * %JOBCTL_PENDING_MASK | %JOBCTL_STOP_CONSUME | %JOBCTL_STOP_SIGMASK | + * %JOBCTL_TRAPPING. If stop signo is being set, the existing signo is + * cleared. If @task is already being killed or exiting, this function + * becomes noop. + * + * CONTEXT: + * Must be called with @task->sighand->siglock held. + * + * RETURNS: + * %true if @mask is set, %false if made noop because @task was dying. + */ +bool task_set_jobctl_pending(struct task_struct *task, unsigned int mask) +{ + BUG_ON(mask & ~(JOBCTL_PENDING_MASK | JOBCTL_STOP_CONSUME | + JOBCTL_STOP_SIGMASK | JOBCTL_TRAPPING)); + BUG_ON((mask & JOBCTL_TRAPPING) && !(mask & JOBCTL_PENDING_MASK)); + + if (unlikely(fatal_signal_pending(task) || (task->flags & PF_EXITING))) + return false; + + if (mask & JOBCTL_STOP_SIGMASK) + task->jobctl &= ~JOBCTL_STOP_SIGMASK; + + task->jobctl |= mask; + return true; +} + +/** * task_clear_jobctl_trapping - clear jobctl trapping bit * @task: target task * @@ -1902,19 +1935,20 @@ static int do_signal_stop(int signr) else WARN_ON_ONCE(!task_ptrace(current)); - current->jobctl &= ~JOBCTL_STOP_SIGMASK; - current->jobctl |= signr | gstop; - sig->group_stop_count = 1; + sig->group_stop_count = 0; + + if (task_set_jobctl_pending(current, signr | gstop)) + sig->group_stop_count++; + for (t = next_thread(current); t != current; t = next_thread(t)) { - t->jobctl &= ~JOBCTL_STOP_SIGMASK; /* * Setting state to TASK_STOPPED for a group * stop is always done with the siglock held, * so this check has no races. */ - if (!(t->flags & PF_EXITING) && !task_is_stopped(t)) { - t->jobctl |= signr | gstop; + if (!task_is_stopped(t) && + task_set_jobctl_pending(t, signr | gstop)) { sig->group_stop_count++; signal_wake_up(t, 0); } -- 1.7.5.2 -- 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/