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From: Qi Zheng In-Reply-To: <20260427034352.6ca48156d613319aac415290@linux-foundation.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: eb98b7nmo46m1qfznyj7fqs93fypttm8 X-Rspam-User: X-Rspamd-Queue-Id: C87FB8000C X-Rspamd-Server: rspam07 X-HE-Tag: 1777287310-862448 X-HE-Meta: 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 vCEIGe+s M+422ZAYnK0anUqwuBoXrn5m4NC82SgdIrvqhkCQ9qt1YbJWEKGFhGLGEAG0KAq4CvdAfu4Llc/SW5oJJbaMZdBqgKs4RhiInVg1VxrlQnjW/wxfze4V6azZ6r0ECx5tYhfLarUy8e7FnnIFo+K+2HfO0eQADRRZliu9ZrUv9a7UYheFfgP6AML/BailUP7/dUIvNqtYdI7EC37zcIzFKgOIQ14ofOpqKOIFXjcWy69Pq7c2YGtiNym8QYq0KvOjBDpuITNtRSnJV4wjfcLx+9kfC4isd7P5KGER4sPEWJFHxXbXXcfym6ZqLejzBTh3rOhK8Nu08FfTJrjRxzKJmA+LCF4RE3kpbzrVy7qgX+aoAgLc= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/27/26 6:43 PM, Andrew Morton wrote: > On Mon, 27 Apr 2026 15:24:10 +0800 Qi Zheng wrote: > >> >> --- a/mm/memcontrol.c >> +++ b/mm/memcontrol.c >> @@ -805,10 +805,15 @@ static long memcg_state_val_in_pages(int idx, long >> val) >> * Used in mod_memcg_state() and mod_memcg_lruvec_state() to avoid >> race with >> * reparenting of non-hierarchical state_locals. >> */ >> -static inline struct mem_cgroup *get_non_dying_memcg_start(struct >> mem_cgroup *memcg) >> +static inline struct mem_cgroup *get_non_dying_memcg_start(struct >> mem_cgroup *memcg, >> + bool *locked) > > Sometimes this is called "locked", sometimes "rcu_locked". Let's be > consistent please. OK. > >> { >> - if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) >> + if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) { >> + *locked = false; >> return memcg; >> + } > > I was thinking we could use a single bit in the task_struct for this: Maybe this isn't the good idea. It feels a bit weird to add a new member to task_struct just to fix a minor bug in mm. :( > > --- a/mm/memcontrol.c~a > +++ a/mm/memcontrol.c > @@ -810,6 +810,8 @@ static inline struct mem_cgroup *get_non > if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) > return memcg; > > + current->foo = 1; > + > rcu_read_lock(); > > while (memcg_is_dying(memcg)) > @@ -820,9 +822,11 @@ static inline struct mem_cgroup *get_non > > static inline void get_non_dying_memcg_end(void) > { > - if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) > + if (current->foo == 0) > return; > > + current->foo = 0; > + > rcu_read_unlock(); > } > #else > _ > > That doesn't work if get_non_dying_memcg_start/get_non_dying_memcg_end > calls can nest? If they can nest then we'd need a counter in the > task_struct. >