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PH0PR13MB4842.namprd13.prod.outlook.com (2603:10b6:510:78::6) by SJ0PR13MB5269.namprd13.prod.outlook.com (2603:10b6:a03:3e1::9) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.6631.29; Fri, 28 Jul 2023 08:13:25 +0000 Received: from PH0PR13MB4842.namprd13.prod.outlook.com ([fe80::fde7:9821:f2d9:101d]) by PH0PR13MB4842.namprd13.prod.outlook.com ([fe80::fde7:9821:f2d9:101d%7]) with mapi id 15.20.6631.026; Fri, 28 Jul 2023 08:13:24 +0000 Date: Fri, 28 Jul 2023 10:13:14 +0200 From: Simon Horman To: Qi Zheng Cc: akpm@linux-foundation.org, david@fromorbit.com, tkhai@ya.ru, vbabka@suse.cz, roman.gushchin@linux.dev, djwong@kernel.org, brauner@kernel.org, paulmck@kernel.org, tytso@mit.edu, steven.price@arm.com, cel@kernel.org, senozhatsky@chromium.org, yujie.liu@intel.com, gregkh@linuxfoundation.org, muchun.song@linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, kvm@vger.kernel.org, xen-devel@lists.xenproject.org, linux-erofs@lists.ozlabs.org, linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com, linux-nfs@vger.kernel.org, linux-mtd@lists.infradead.org, rcu@vger.kernel.org, netdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-arm-msm@vger.kernel.org, dm-devel@redhat.com, linux-raid@vger.kernel.org, linux-bcache@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, linux-btrfs@vger.kernel.org, Muchun Song Subject: Re: [PATCH v3 04/49] mm: shrinker: remove redundant shrinker_rwsem in debugfs operations Message-ID: References: <20230727080502.77895-1-zhengqi.arch@bytedance.com> <20230727080502.77895-5-zhengqi.arch@bytedance.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230727080502.77895-5-zhengqi.arch@bytedance.com> X-ClientProxiedBy: AM0PR02CA0114.eurprd02.prod.outlook.com (2603:10a6:20b:28c::11) To PH0PR13MB4842.namprd13.prod.outlook.com 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Reviewed-by: Muchun Song > --- > mm/shrinker_debug.c | 14 -------------- > 1 file changed, 14 deletions(-) > > diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c > index 3ab53fad8876..f1becfd45853 100644 > --- a/mm/shrinker_debug.c > +++ b/mm/shrinker_debug.c > @@ -55,11 +55,6 @@ static int shrinker_debugfs_count_show(struct seq_file *m, void *v) > if (!count_per_node) > return -ENOMEM; > > - ret = down_read_killable(&shrinker_rwsem); > - if (ret) { > - kfree(count_per_node); > - return ret; > - } > rcu_read_lock(); Hi Qi Zheng, As can be seen in the next hunk, this function returns 'ret'. However, with this change 'ret' is uninitialised unless signal_pending() returns non-zero in the while loop below. This is flagged in a clan-16 W=1 build. mm/shrinker_debug.c:87:11: warning: variable 'ret' is used uninitialized whenever 'do' loop exits because its condition is false [-Wsometimes-uninitialized] } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ mm/shrinker_debug.c:92:9: note: uninitialized use occurs here return ret; ^~~ mm/shrinker_debug.c:87:11: note: remove the condition if it is always true } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1 mm/shrinker_debug.c:77:7: warning: variable 'ret' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized] if (!memcg_aware) { ^~~~~~~~~~~~ mm/shrinker_debug.c:92:9: note: uninitialized use occurs here return ret; ^~~ mm/shrinker_debug.c:77:3: note: remove the 'if' if its condition is always false if (!memcg_aware) { ^~~~~~~~~~~~~~~~~~~ mm/shrinker_debug.c:52:9: note: initialize the variable 'ret' to silence this warning int ret, nid; ^ = 0 > > memcg_aware = shrinker->flags & SHRINKER_MEMCG_AWARE; > @@ -92,7 +87,6 @@ static int shrinker_debugfs_count_show(struct seq_file *m, void *v) > } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL); > > rcu_read_unlock(); > - up_read(&shrinker_rwsem); > > kfree(count_per_node); > return ret; ...