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([2601:188:c102:b180:1f8b:71d0:77b1:1f6e]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-882862c9854sm114279556d6.4.2025.11.18.06.33.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 18 Nov 2025 06:33:55 -0800 (PST) From: Waiman Long X-Google-Original-From: Waiman Long Message-ID: <45bdbbd5-9c82-4f5f-864b-9f01e356d8ef@redhat.com> Date: Tue, 18 Nov 2025 09:33:53 -0500 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHv6 1/2] cgroup/cpuset: Introduce cpuset_cpus_allowed_locked() To: Pingfan Liu , Waiman Long Cc: cgroups@vger.kernel.org, Chen Ridong , Peter Zijlstra , Juri Lelli , Pierre Gondois , Ingo Molnar , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Tejun Heo , Johannes Weiner , mkoutny@suse.com, linux-kernel@vger.kernel.org References: <20251117092732.16419-1-piliu@redhat.com> <20251117092732.16419-2-piliu@redhat.com> <97ec2e86-cb4f-4467-8930-d390519f12a6@redhat.com> Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 11/18/25 1:30 AM, Pingfan Liu wrote: > On Tue, Nov 18, 2025 at 4:37 AM Waiman Long wrote: >> On 11/17/25 4:27 AM, Pingfan Liu wrote: >>> cpuset_cpus_allowed() uses a reader lock that is sleepable under RT, >>> which means it cannot be called inside raw_spin_lock_t context. >>> >>> Introduce a new cpuset_cpus_allowed_locked() helper that performs the >>> same function as cpuset_cpus_allowed() except that the caller must have >>> acquired the cpuset_mutex so that no further locking will be needed. >>> >>> Suggested-by: Waiman Long >>> Signed-off-by: Pingfan Liu >>> Cc: Waiman Long >>> Cc: Tejun Heo >>> Cc: Johannes Weiner >>> Cc: "Michal Koutný" >>> Cc: linux-kernel@vger.kernel.org >>> To: cgroups@vger.kernel.org >>> --- >>> include/linux/cpuset.h | 1 + >>> kernel/cgroup/cpuset.c | 51 +++++++++++++++++++++++++++++------------- >>> 2 files changed, 37 insertions(+), 15 deletions(-) >>> >>> diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h >>> index 2ddb256187b51..e057a3123791e 100644 >>> --- a/include/linux/cpuset.h >>> +++ b/include/linux/cpuset.h >>> @@ -75,6 +75,7 @@ extern void dec_dl_tasks_cs(struct task_struct *task); >>> extern void cpuset_lock(void); >>> extern void cpuset_unlock(void); >>> extern void cpuset_cpus_allowed(struct task_struct *p, struct cpumask *mask); >>> +extern void cpuset_cpus_allowed_locked(struct task_struct *p, struct cpumask *mask); >>> extern bool cpuset_cpus_allowed_fallback(struct task_struct *p); >>> extern bool cpuset_cpu_is_isolated(int cpu); >>> extern nodemask_t cpuset_mems_allowed(struct task_struct *p); >> Ah, the following code should be added to to !CONFIG_CPUSETS section >> after cpuset_cpus_allowed(). >> >> #define cpuset_cpus_allowed_locked(p, m) cpuset_cpus_allowed(p, m) >> >> Or you can add another inline function that just calls >> cpuset_cpus_allowed(). >> > It may be better to make cpuset_cpus_allowed() call > cpuset_cpus_allowed_locked(), following the call chain used under > CONFIG_CPUSETS case. That is fine too. Cheers, Longman > > Thanks, > > Pingfan >