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[195.135.220.15]) by mx.google.com with ESMTPS id r2si855305ejf.139.2019.03.27.06.17.20 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 27 Mar 2019 06:17:20 -0700 (PDT) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org 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 EF780AFE4; Wed, 27 Mar 2019 13:17:19 +0000 (UTC) Date: Wed, 27 Mar 2019 14:17:18 +0100 From: Michal Hocko To: Qian Cai Cc: akpm@linux-foundation.org, catalin.marinas@arm.com, cl@linux.com, willy@infradead.org, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4] kmemleak: survive in a low-memory situation Message-ID: <20190327131718.GJ11927@dhcp22.suse.cz> References: <20190327005948.24263-1-cai@lca.pw> <20190327084432.GA11927@dhcp22.suse.cz> <651bd879-c8c0-b162-fee7-1e523904b14e@lca.pw> <20190327114458.GF11927@dhcp22.suse.cz> <68cff59d-2b0e-5a7b-bca9-36784522059b@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <68cff59d-2b0e-5a7b-bca9-36784522059b@lca.pw> User-Agent: Mutt/1.10.1 (2018-07-13) 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 Wed 27-03-19 09:05:31, Qian Cai wrote: > On 3/27/19 7:44 AM, Michal Hocko wrote> What? Normal spin lock implementation > doesn't disable interrupts. So > > either I misunderstand what you are saying or you seem to be confused. > > the thing is that in_atomic relies on preempt_count to work properly and > > if you have CONFIG_PREEMPT_COUNT=n then you simply never know whether > > preemption is disabled so you do not know that a spin_lock is held. > > irqs_disabled on the other hand checks whether arch specific flag for > > IRQs handling is set (or cleared). So you would only catch irq safe spin > > locks with the above check. > > Exactly, because kmemleak_alloc() is only called in a few call sites, slab > allocation, neigh_hash_alloc(), alloc_page_ext(), sg_kmalloc(), > early_amd_iommu_init() and blk_mq_alloc_rqs(), my review does not yield any of > those holding irq unsafe spinlocks. I do not understand. What about a regular kmalloc(GFP_NOWAIT) callers with a simple spinlock held? -- Michal Hocko SUSE Labs