linux-kernel - Re: [PATCH] mm/kmemleak: Prevent soft lockup in kmemleak

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Message-ID: <af778779-77b8-15db-d5dc-36c4992483b3@redhat.com>
Date:   Thu, 20 Oct 2022 21:22:14 -0400
From:   Waiman Long <longman@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Catalin Marinas <catalin.marinas@....com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Muchun Song <songmuchun@...edance.com>
Subject: Re: [PATCH] mm/kmemleak: Prevent soft lockup in kmemleak_scan()'s
 object iteration loops


On 10/20/22 20:58, Andrew Morton wrote:
> On Thu, 20 Oct 2022 13:56:19 -0400 Waiman Long <longman@...hat.com> wrote:
>
>> Commit 6edda04ccc7c ("mm/kmemleak: prevent soft lockup in first object
>> iteration loop of kmemleak_scan()") adds cond_resched() in the first
>> object iteration loop of kmemleak_scan(). However, it turns that the
>> 2nd objection iteration loop can still cause soft lockup to happen in
>> some cases. So add a cond_resched() call in the 2nd and 3rd loops as
>> well to prevent that and for completeness.
>>
> Seems reasonable, although not an object of beauty.
>
> We didn't include a Fixes: or cc:stable in 6edda04ccc7c, even though it
> addresses softlockups.  I think I'll add a cc:stable to this, with a
> Fixes:6edda04ccc7c.  So any kenrel which included 6edda04ccc7c will
> hopefully add this as well.

That sounds good to me. I consider commit 6edda04ccc7c incomplete and 
this patch complete it. Technically it can be considered a fix.

Thanks,
Longman