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[198.145.29.99]) by mx.google.com with ESMTPS id 92si10273960plf.299.2019.06.01.06.25.29 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 01 Jun 2019 06:25:29 -0700 (PDT) Received-SPF: pass (google.com: domain of sashal@kernel.org designates 198.145.29.99 as permitted sender) client-ip=198.145.29.99; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=DGXicQ4V; spf=pass (google.com: domain of sashal@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=sashal@kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A3FE8273AC; Sat, 1 Jun 2019 13:25:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559395528; bh=2gwOA4oXprxT5utFsmFxHJm6LeTnp8J00kQIUqH1TKQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DGXicQ4V7Hdnq14PC3+r2NtPJNQcUo/K87bCRiCW7JdRPVfhwNT/3CmDHwcCNbdxk NPY/Oh9mp2EvwXCilUwa54YbFRUM1h5OOeOl5YzZwFANuZbZg3TESI8daUJYC/+O4P hNVJgLy6OkudECk6pqq/Afr7TSrBWBGI69bUuMmA= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Qian Cai , Andrew Morton , Vlastimil Babka , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Linus Torvalds , Sasha Levin , linux-mm@kvack.org Subject: [PATCH AUTOSEL 4.9 10/74] mm/slab.c: fix an infinite loop in leaks_show() Date: Sat, 1 Jun 2019 09:23:57 -0400 Message-Id: <20190601132501.27021-10-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190601132501.27021-1-sashal@kernel.org> References: <20190601132501.27021-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit 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: From: Qian Cai [ Upstream commit 745e10146c31b1c6ed3326286704ae251b17f663 ] "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(), do { set_store_user_clean(cachep); drain_cpu_caches(cachep); ... } while (!is_store_user_clean(cachep)); For example, do_drain slabs_destroy slab_destroy kmem_cache_free __cache_free ___cache_free kmemleak_free_recursive delete_object_full __delete_object put_object free_object_rcu kmem_cache_free cache_free_debugcheck --> dirty kmemleak_object One approach is to check cachep->name and skip both kmemleak_object and debug_objects_cache in leaks_show(). The other is to set store_user_clean after drain_cpu_caches() which leaves a small window between drain_cpu_caches() and set_store_user_clean() where per-CPU caches could be dirty again lead to slightly wrong information has been stored but could also speed up things significantly which sounds like a good compromise. For example, # cat /proc/slab_allocators 0m42.778s # 1st approach 0m0.737s # 2nd approach [akpm@linux-foundation.org: tweak comment] Link: http://lkml.kernel.org/r/20190411032635.10325-1-cai@lca.pw Fixes: d31676dfde25 ("mm/slab: alternative implementation for DEBUG_SLAB_LEAK") Signed-off-by: Qian Cai Reviewed-by: Andrew Morton Cc: Vlastimil Babka Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- mm/slab.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/mm/slab.c b/mm/slab.c index d2c0499c6b15d..9547f02b4af96 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -4365,8 +4365,12 @@ static int leaks_show(struct seq_file *m, void *p) * whole processing. */ do { - set_store_user_clean(cachep); drain_cpu_caches(cachep); + /* + * drain_cpu_caches() could make kmemleak_object and + * debug_objects_cache dirty, so reset afterwards. + */ + set_store_user_clean(cachep); x[1] = 0; -- 2.20.1