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From: Muchun Song In-Reply-To: Date: Wed, 24 Jul 2024 10:26:24 +0800 Cc: Muchun Song , Johannes Weiner , Michal Hocko , Roman Gushchin , Andrew Morton , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Transfer-Encoding: 7bit Message-Id: References: <20240722070810.46016-1-songmuchun@bytedance.com> To: Shakeel Butt X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: D43E41A0009 X-Stat-Signature: 95w663zbycwxbwn7yxtyh8jq4rukhabk X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1721788024-890404 X-HE-Meta: U2FsdGVkX1/TfJTL04WEjxQN4M/zuI2VbgMHB0bz8Ed16/T4KSke43XLqUl5taUxM3VDB/Fg8XBj7EmVRcmI2UNp2aZlXPSesPybCAuk614QX+jotFJ53SpFOBoP5YcMeWYIzQK8WsaWJ89XQe3H2/brVBrKkJ3PCSNXWfqg5GrDxc+bdBA5S5NsngRTxWOKwHVRuZu4jUFOCiN6VKZoC3XKQB6zKsaD0qfnh0H+zDDE1wX0IM1H8x8ZVCuNeTK7JmfI5tqcW0BnV3hiTAWkhpuBKSvbJmsUe5rlEMT8YrMOHEzYXKfYeqqgNbCjpclMzejy/iqmV8NjIy3QkkB7R9dtAhD1fBLlSQMsL6H2w5WdqTjcxu3/GyW5W9zFndcLHEFc0jevf4PSrOAOy+VXgxfasHOxPp9e7u70PHmogulvHklrunWPZqEmeVU5oN4HnbEhmVIq9f4nl7ZMWw7jXbCrr0VyGsMhtLmHuXSc4Y0Kt+j6Yt+woeUDxBEpcW4PG71lHqXSlSRgLABhUO1vl/K88OVRq8s8DFFS5QTJ7FreTQOIueJL+XSb2xnhTDnd6yPm46JPuYrBTtLTq2dfXpK/tkKfrV8tQad9Bk1ED7dmbyQelutwA6cfQmoZ+5AJZ9+YxwcZxkbqmyzB8xjC1C9q3FkDIyPpJ4uHFfwKsHdK8m/mV+xeUdjQJSoKaQN+KtzI4/2ijk8tuTqfo4sGJ4WxVbwWyToASusnYDTOYDqpcT/kDeYcm73KF0DfeScxoGPDAugZEt16fLLVaC00qPupc/1yvo8rYeEROdZ8og0CrO5keFKP8kMULdOfrVQuKMiC+diI1u0nL+goZ8Sixm88BqWbVNyAA9lOd/KlBhBfbIX8rRuTdz1SF09NsNU7Iu972alK2Ne8u7+sTn3x3/nHD2nJVzw22Wic6cqarU+EhmHpIFySk8qBB3v/PvObWlE184RFmKZWFGqnDwF PaiWMRy8 tmcdB6OFf2uAa6y0mjnZDFrUtFUkWa2Ooc93u1nalCLu3zuzVkrxD/mDrLnQVOqrP55/Wn3a+gTAGBUuBPYwaE4+TSXal4uuV0Gt6NhJiyXBfdx58H0xdLgtrLEuAGBkrmSy61L77AdsTJl22V+TG60EB3kqqllWw2k1KaEJOEwl1KdDjkF9hzDV/QkplsgvMhn3B 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: List-Subscribe: List-Unsubscribe: > On Jul 24, 2024, at 02:39, Shakeel Butt wrote: > > On Mon, Jul 22, 2024 at 03:08:10PM GMT, Muchun Song wrote: >> The obj_cgroup_memcg() is supposed to safe to prevent the returned >> memory cgroup from being freed only when the caller is holding the >> rcu read lock or objcg_lock or cgroup_mutex. It is very easy to >> ignore thoes conditions when users call some upper APIs which call >> obj_cgroup_memcg() internally like mem_cgroup_from_slab_obj() (See >> the link below). So it is better to add lockdep assertion to >> obj_cgroup_memcg() to find those issues ASAP. >> >> Because there is no user of obj_cgroup_memcg() holding objcg_lock >> to make the returned memory cgroup safe, do not add objcg_lock >> assertion (We should export objcg_lock if we really want to do) >> and leave a comment to indicate it is intentional. >> > > Do we expect non-memcg code to access objcg_lock? To me this is some > internal implementation detail of memcg and should not be accessible > outside memcg code. So, I would recommend to not mention objcg_lock at > all. Also make sense. Will update next version.