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Date:   Fri, 21 Aug 2020 13:20:41 +0200
From:   Oleg Nesterov <oleg@redhat.com>
To:     Davidlohr Bueso <dave@stgolabs.net>
Cc:     akpm@linux-foundation.org, catalin.marinas@arm.com,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Davidlohr Bueso <dbueso@suse.de>
Subject: Re: [PATCH] mm/kmemleak: rely on rcu for task stack scanning
Message-ID: <20200821112041.GH4546@redhat.com>
References: <20200820203902.11308-1-dave@stgolabs.net>
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On 08/20, Davidlohr Bueso wrote:
>
> @@ -1471,15 +1471,15 @@ static void kmemleak_scan(void)
>  	if (kmemleak_stack_scan) {
>  		struct task_struct *p, *g;
>  
> -		read_lock(&tasklist_lock);
> -		do_each_thread(g, p) {
> +		rcu_read_lock();
> +		for_each_process_thread(g, p) {
>  			void *stack = try_get_task_stack(p);
>  			if (stack) {
>  				scan_block(stack, stack + THREAD_SIZE, NULL);
>  				put_task_stack(p);
>  			}
> -		} while_each_thread(g, p);
> -		read_unlock(&tasklist_lock);
> +		}
> +		rcu_read_unlock();

Acked-by: Oleg Nesterov <oleg@redhat.com>