Re: [PATCH] staging: android/lowmemorykiller: Don't grabtasklist_lock

[Oleg Nesterov]

On 02/01, Anton Vorontsov wrote:
>
> @@ -132,7 +133,7 @@ static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
>  	}
>  	selected_oom_adj = min_adj;
>
> -	read_lock(&tasklist_lock);
> +	rcu_read_lock();

This has the same problem, force_sig() becomes unsafe.

Why do you need force_? Do you really want to kill /sbin/init (or sub-namespace
init) ?

We could change force_sig_info() to use lock_task_sighand(), but I'd like to
avoid this. Imho, this interface should be cleanuped, and it should be used
for synchronous signals only.

With or without this patch, sig == NULL is not possible but !mm is not right,
there could be other other threads with mm != NULL.

Oleg.

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