linux-kernel - Re: [PATCH] slab: fix an infinite loop in leaks

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Message-ID: <02049855-d37f-965e-12f7-f2549cae73ec@lca.pw>
Date:   Thu, 11 Apr 2019 07:08:23 -0400
From:   Qian Cai <cai@....pw>
To:     Vlastimil Babka <vbabka@...e.cz>, akpm@...ux-foundation.org
Cc:     cl@...ux.com, penberg@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        "Tobin C. Harding" <tobin@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>
Subject: Re: [PATCH] slab: fix an infinite loop in leaks_show()



On 4/11/19 4:20 AM, Vlastimil Babka wrote:
> On 4/11/19 5:26 AM, Qian Cai wrote:
>> "cat /proc/slab_allocators" could hang forever on SMP machines with
>> kmemleak or object debugging enabled due to other CPUs running do_drain()
>> will keep making kmemleak_object or debug_objects_cache dirty and unable
>> to escape the first loop in leaks_show(),
> 
> So what if we don't remove SLAB (yet?) but start removing the debugging
> functionality that has been broken for years and nobody noticed. I think
> Linus already mentioned that we remove at least the
> /proc/slab_allocators file...

In my experience, 2-year isn't that long for debugging features to be silently
broken with SLAB where kmemleak is broken for more than 4-year there. See
92d1d07daad6 ("mm/slab.c: kmemleak no scan alien caches").