Re: [EDT][PATCH] kernel/exit.c : Fix missing read_unlock

[Oleg Nesterov <oleg@redhat.com>]

On 05/21, Maninder Singh wrote:
>
>  EP-F6AA0618C49C4AEDA73BFF1B39950BAB
> Hi,
>
> From: Maninder Singh <maninder1.s@samsung.com>
>
> Subject: [PATCH 1/1] kernel/exit.c : Fix missing task_unlock
>
> This patch adds missing read_unlock if do_wait_thread or ptrace_do_wait
> returns non zero.

Confused...

wait_consider_task() should drop tasklist_lock if it returns non-zero?


> --- a/kernel/exit.c
> +++ b/kernel/exit.c
> @@ -1486,12 +1486,16 @@ repeat:
>  	tsk = current;
>  	do {
>  		retval = do_wait_thread(wo, tsk);
> -		if (retval)
> +		if (retval) {
> +			read_unlock(&tasklist_lock);
>  			goto end;
> +		}
>
>  		retval = ptrace_do_wait(wo, tsk);
> -		if (retval)
> +		if (retval) {
> +			read_unlock(&tasklist_lock);
>  			goto end;
> +		}

Well, the patch is obviously wrong. Because, again, tasklist_lock was
already unlocked if (say) wait_task_zombie() reaps a child.

If you think there is a case which forgets to unlock, please tell us
more.

Oleg.