linux-kernel - [PATCH] proc: don't confuse /bin/ps by zombie delay_group

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Message-ID: <20080830170841.GA7887@tv-sign.ru>
Date:	Sat, 30 Aug 2008 21:08:41 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Albert Cahalan <acahalan@...il.com>,
	Alexey Dobriyan <adobriyan@...nvz.org>,
	Michael Kerrisk <mtk.manpages@...glemail.com>,
	Roland McGrath <roland@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] proc: don't confuse /bin/ps by zombie delay_group_leader's

When the main thread exits,

	void *do_thread(void *arg)
	{
		pause();
		return NULL;
	}

	int main(void)
	{
		pthread_t thr;
		pthread_create(&thr, NULL, do_thread, NULL);

		syscall(__NR_exit, 0);
		return 0;
	}

/bin/ps's output looks really confusing, as if the whole process is dead.
I think this even looks like a kernel bug to the user, because it sees a
zombie which is not going to be reaped.

Change get_task_state() to report "S (sleeping)" in this case. Still not
perfect because the task can be confused with the kernel thread (its ->mm
is NULL), but imho better anyway.

Also, uninline get_task_state(), it has 2 callers.

Signed-off-by: Oleg Nesterov <oleg@...sign.ru>

--- 2.6.27-rc4/fs/proc/array.c~ZOMBIE_LEADER	2008-07-30 13:12:47.000000000 +0400
+++ 2.6.27-rc4/fs/proc/array.c	2008-08-30 18:17:10.000000000 +0400
@@ -146,10 +146,14 @@ static const char *task_state_array[] = 
 	"X (dead)"		/* 32 */
 };
 
-static inline const char *get_task_state(struct task_struct *tsk)
+static const char *get_task_state(struct task_struct *tsk)
 {
-	unsigned int state = (tsk->state & TASK_REPORT) | tsk->exit_state;
 	const char **p = &task_state_array[0];
+	unsigned int state = tsk->exit_state | (tsk->state & TASK_REPORT);
+
+	/* don't confuse /bin/ps if the whole process is not dead */
+	if (tsk->exit_state && delay_group_leader(tsk))
+		state = TASK_INTERRUPTIBLE;
 
 	while (state) {
 		p++;

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