Attachment 865176 Details for Bug 958505 – [PATCH] kill DEAD->ZOMBIE transition

[patch] [PATCH] kill DEAD->ZOMBIE transition

ALL.p (text/plain), 3.42 KB, created by Oleg Nesterov on 2014-02-19 18:29:54 UTC

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Creator: Oleg Nesterov

Created: 2014-02-19 18:29:54 UTC

Size: 3.42 KB

patch

obsolete

>diff --git a/include/linux/sched.h b/include/linux/sched.h
>index a781dec..6b4f55d 100644
>--- a/include/linux/sched.h
>+++ b/include/linux/sched.h
>@@ -206,6 +206,9 @@ print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq);
> /* in tsk->exit_state */
> #define EXIT_ZOMBIE		16
> #define EXIT_DEAD		32
>+
>+#define EXIT_TRACE		(EXIT_ZOMBIE | EXIT_DEAD)
>+
> /* in tsk->state again */
> #define TASK_DEAD		64
> #define TASK_WAKEKILL		128
>diff --git a/kernel/exit.c b/kernel/exit.c
>index 1e77fc6..10a1528 100644
>--- a/kernel/exit.c
>+++ b/kernel/exit.c
>@@ -1038,17 +1038,13 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
> 		return wait_noreap_copyout(wo, p, pid, uid, why, status);
> 	}
> 
>+	traced = ptrace_reparented(p);
> 	/*
>-	 * Try to move the task's state to DEAD
>-	 * only one thread is allowed to do this:
>+	 * Move the task's state to DEAD/TRACE, only one thread can do this.
> 	 */
>-	state = xchg(&p->exit_state, EXIT_DEAD);
>-	if (state != EXIT_ZOMBIE) {
>-		BUG_ON(state != EXIT_DEAD);
>+	state = traced && thread_group_leader(p) ? EXIT_TRACE : EXIT_DEAD;
>+	if (cmpxchg(&p->exit_state, EXIT_ZOMBIE, state) != EXIT_ZOMBIE)
> 		return 0;
>-	}
>-
>-	traced = ptrace_reparented(p);
> 	/*
> 	 * It can be ptraced but not reparented, check
> 	 * thread_group_leader() to filter out sub-threads.
>@@ -1109,7 +1105,7 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
> 
> 	/*
> 	 * Now we are sure this task is interesting, and no other
>-	 * thread can reap it because we set its state to EXIT_DEAD.
>+	 * thread can reap it because we its state == DEAD/TRACE.
> 	 */
> 	read_unlock(&tasklist_lock);
> 
>@@ -1146,22 +1142,19 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
> 	if (!retval)
> 		retval = pid;
> 
>-	if (traced) {
>+	if (state == EXIT_TRACE) {
> 		write_lock_irq(&tasklist_lock);
> 		/* We dropped tasklist, ptracer could die and untrace */
> 		ptrace_unlink(p);
>-		/*
>-		 * If this is not a sub-thread, notify the parent.
>-		 * If parent wants a zombie, don't release it now.
>-		 */
>-		if (thread_group_leader(p) &&
>-		    !do_notify_parent(p, p->exit_signal)) {
>-			p->exit_state = EXIT_ZOMBIE;
>-			p = NULL;
>-		}
>+
>+		/* If parent wants a zombie, don't release it now */
>+		state = EXIT_ZOMBIE;
>+		if (do_notify_parent(p, p->exit_signal))
>+			state = EXIT_DEAD;
>+		p->exit_state = state;
> 		write_unlock_irq(&tasklist_lock);
> 	}
>-	if (p != NULL)
>+	if (state == EXIT_DEAD)
> 		release_task(p);
> 
> 	return retval;
>@@ -1338,7 +1331,13 @@ static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
> static int wait_consider_task(struct wait_opts *wo, int ptrace,
> 				struct task_struct *p)
> {
>-	int ret = eligible_child(wo, p);
>+	int ret;
>+
>+	/* dead body doesn't have much to contribute */
>+	if (unlikely(p->exit_state == EXIT_DEAD))
>+		return 0;
>+
>+	ret = eligible_child(wo, p);
> 	if (!ret)
> 		return ret;
> 
>@@ -1356,13 +1355,12 @@ static int wait_consider_task(struct wait_opts *wo, int ptrace,
> 		return 0;
> 	}
> 
>-	/* dead body doesn't have much to contribute */
>-	if (unlikely(p->exit_state == EXIT_DEAD)) {
>+	if (unlikely(p->exit_state == EXIT_TRACE)) {
> 		/*
>-		 * But do not ignore this task until the tracer does
>-		 * wait_task_zombie()->do_notify_parent().
>+		 * ptrace == 0 means we are the natural parent. In this case
>+		 * we should clear notask_error, debugger will notify us.
> 		 */
>-		if (likely(!ptrace) && unlikely(ptrace_reparented(p)))
>+		if (likely(!ptrace))
> 			wo->notask_error = 0;
> 		return 0;
> 	}

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Attachments on bug 958505: 742272 | 758391 | 758857 | 864639 | 865176