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[195.135.220.15]) by mx.google.com with ESMTPS id fx19si2401482ejb.350.2019.04.16.14.19.28 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 16 Apr 2019 14:19:28 -0700 (PDT) Received-SPF: pass (google.com: domain of vbabka@suse.cz designates 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=pass (google.com: domain of vbabka@suse.cz designates 195.135.220.15 as permitted sender) smtp.mailfrom=vbabka@suse.cz X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id DE1EAAC1B; Tue, 16 Apr 2019 21:19:27 +0000 (UTC) Subject: Re: [PATCH] slab: remove store_stackinfo() To: Thomas Gleixner Cc: Qian Cai , akpm@linux-foundation.org, luto@kernel.org, jpoimboe@redhat.com, sean.j.christopherson@intel.com, penberg@kernel.org, rientjes@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20190416142258.18694-1-cai@lca.pw> <902fed9c-9655-a241-677d-5fa11b6c95a1@suse.cz> From: Vlastimil Babka Message-ID: <235d7500-8235-c7d4-0d6f-4d069133bd8d@suse.cz> Date: Tue, 16 Apr 2019 23:19:11 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 4/16/2019 8:50 PM, Thomas Gleixner wrote: > On Tue, 16 Apr 2019, Vlastimil Babka wrote: > >> On 4/16/19 4:22 PM, Qian Cai wrote: >>> store_stackinfo() does not seem used in actual SLAB debugging. >>> Potentially, it could be added to check_poison_obj() to provide more >>> information, but this seems like an overkill due to the declining >>> popularity of the SLAB, so just remove it instead. >>> >>> Signed-off-by: Qian Cai >> >> I've acked Thomas' version already which was narrower, but no objection >> to remove more stuff on top of that. Linus (and I later in another >> thread) already pointed out /proc/slab_allocators. It only takes a look >> at add_caller() there to not regret removing that one. > > The issue why I was looking at this was a krobot complaint about the kernel > crashing in that stack store function with my stackguard series applied. It > was broken before the stackguard pages already, it just went unnoticed. > > As you explained, nobody is caring about DEBUG_SLAB + DEBUG_PAGEALLOC > anyway, so I'm happy to not care about krobot tripping over it either. > > So we have 3 options: > > 1) I ignore it and merge the stack guard series w/o it > > 2) I can carry the minimal fix or Qian's version in the stackguard > branch > > 3) We ship that minimal fix to Linus right now and then everyone can > base their stuff on top independently. I think #3 is overkill for something that was broken for who knows how long and nobody noticed. I'd go with 2) and perhaps Qian's version as nobody AFAIK uses the caller+cpu as well as the stack trace. For Qian's version also: Acked-by: Vlastimil Babka > #3 is probably the right thing to do. > > Thanks, > > tglx >