2008-08-30 17:04:18

by Oleg Nesterov

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 <[email protected]>

--- 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++;

2008-09-01 01:10:34

by Roland McGrath

Subject: Re: [PATCH] proc: don't confuse /bin/ps by zombie delay_group_leader's

I don't think it's right to change /proc/pid/task/tid/status this way.
The real status is true and correct for the individual task, no matter what.
If you want to change /proc/pid/status, then you ought to split it into
proc_tgid_status and proc_tid_status variants to differ this way.

I don't really have an opinion either way about this for /proc/pid/status.
We've known it behaved this way for a very long time, and I've always
considered it procps's problem to display such situations in ways that
users find most useful. It can already quickly tell that situation by a
"Threads:" line with >1 when "State:" says "Z". If you do change it, it
might be nicer to display it as a (compatible) special case:

State: S (delayed-leader)


Thanks,
Roland