Re: Add all thread stats for TASKSTATS_CMD_ATTR_TGID (v5)

[Oleg Nesterov]

On 09/18, Guillaume Chazarain wrote:
>
> @@ -508,7 +543,7 @@ void taskstats_exit(struct task_struct *
>  	if (!stats)
>  		goto err;
>  
> -	memcpy(stats, tsk->signal->stats, sizeof(*stats));
> +	fill_tgid(tsk->pid, tsk, stats);

No, no, this is wrong.

tsk->signal->stats contains the accumulated info about the already exited
threads, we shouldn't throw it out.

Also, fill_tgid() doesn't make sense here, current is the last live sub-thread.


Hmm. We have another race here. There is no guarantee that tsk->signal->stats
covers all sub-threads, as it is supposed to be. It is quite possible that
another sub-thread decremented ->signal->live before us, but didn't complete
taskstats_exit()->fill_tgid_exit() yet.

Oleg.

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