linux-kernel - Re: [PATCH] mm/kmemleak: rely on rcu for task stack scanning

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Date:   Fri, 21 Aug 2020 19:09:31 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Davidlohr Bueso <dave@...olabs.net>
Cc:     akpm@...ux-foundation.org, oleg@...hat.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH] mm/kmemleak: rely on rcu for task stack scanning

On Thu, Aug 20, 2020 at 01:39:02PM -0700, Davidlohr Bueso wrote:
> kmemleak_scan() currently relies on the big tasklist_lock
> hammer to stabilize iterating through the tasklist. Instead,
> this patch proposes simply using rcu along with the rcu-safe
> for_each_process_thread flavor (without changing scan semantics),
> which doesn't make use of next_thread/p->thread_group and thus
> cannot race with exit. Furthermore, any races with fork()
> and not seeing the new child should be benign as it's not
> running yet and can also be detected by the next scan.
> 
> Signed-off-by: Davidlohr Bueso <dbueso@...e.de>

As long as the kernel thread stack is still around (kmemleak does use
try_get_task_stack()), I'm fine with the change:

Acked-by: Catalin Marinas <catalin.marinas@....com>