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([2601:188:c102:b180:1f8b:71d0:77b1:1f6e]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8c6e37c661fsm76246685a.1.2026.01.22.18.37.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 22 Jan 2026 18:37:11 -0800 (PST) From: Waiman Long X-Google-Original-From: Waiman Long Message-ID: <5a6bd6f6-7dda-4665-9308-4ae8b0d64c9f@redhat.com> Date: Thu, 22 Jan 2026 21:37:09 -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: [PATCH -next] sched/isolation: Use static_branch_enable_cpuslocked() on housekeeping_update To: Chen Ridong , tj@kernel.org, hannes@cmpxchg.org, mkoutny@suse.com, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, frederic@kernel.org Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, lujialin4@huawei.com References: <20260122080902.2312721-1-chenridong@huaweicloud.com> Content-Language: en-US In-Reply-To: <20260122080902.2312721-1-chenridong@huaweicloud.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 1/22/26 3:09 AM, Chen Ridong wrote: > From: Chen Ridong > > The warning is observed: > > WARNING: possible recursive locking detected > 6.19.0-rc6-next-20260121 #1046 Not tainted > -------------------------------------------- > test_cpuset_prs/686 is trying to acquire lock: > (cpu_hotplug_lock){++++}-{0:0}, at: static_key_enable+0xd/0x20 > > but task is already holding lock: > (cpu_hotplug_lock){++++}-{0:0}, at: cpuset_partition_write+0x72/0x10 > > other info that might help us debug this: > Possible unsafe locking scenario: > > CPU0 > ---- > lock(cpu_hotplug_lock); > lock(cpu_hotplug_lock); > > *** DEADLOCK *** > > May be due to missing lock nesting notation > > stack backtrace: > CPU: 11 UID: 0 PID: 686 Comm: test_cpuset_prs 6.19.0-rc6-next-20260121 #1 > Call Trace: > > dump_stack_lvl+0x82/0xd0 > print_deadlock_bug+0x288/0x3c0 > __lock_acquire+0x1506/0x27f0 > lock_acquire+0xc8/0x2d0 > ? static_key_enable+0xd/0x20 > cpus_read_lock+0x3b/0xd0 > ? static_key_enable+0xd/0x20 > static_key_enable+0xd/0x20 > housekeeping_update+0xe7/0x1b0 > update_prstate+0x3f2/0x580 > cpuset_partition_write+0x98/0x100 > kernfs_fop_write_iter+0x14e/0x200 > vfs_write+0x367/0x510 > ksys_write+0x66/0xe0 > do_syscall_64+0x6b/0x390 > entry_SYSCALL_64_after_hwframe+0x76/0x7e > RIP: 0033:0x7f824cf8c887 > > The commit 7109b22e6581 ("cpuset: Update HK_TYPE_DOMAIN cpumask from > cpuset") introduced housekeeping_update, which calls static_branch_enable > while cpu_read_lock() is held. Since static_key_enable itself also acquires > cpu_read_lock, this leads to a lockdep warning. To resolve this issue, > replace the call to static_key_enable with static_branch_enable_cpuslocked. > > Fixes: 7109b22e6581 ("cpuset: Update HK_TYPE_DOMAIN cpumask from cpuset") > Signed-off-by: Chen Ridong > --- > kernel/cgroup/cpuset.c | 2 -- > kernel/sched/isolation.c | 4 +++- > 2 files changed, 3 insertions(+), 3 deletions(-) > > diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c > index 392ce795656d..a26ccff55bb7 100644 > --- a/kernel/cgroup/cpuset.c > +++ b/kernel/cgroup/cpuset.c > @@ -1308,8 +1308,6 @@ static void update_isolation_cpumasks(void) > if (!isolated_cpus_updating) > return; > > - lockdep_assert_cpus_held(); > - > ret = housekeeping_update(isolated_cpus); > WARN_ON_ONCE(ret < 0); > > diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c > index ef152d401fe2..3b725d39c06e 100644 > --- a/kernel/sched/isolation.c > +++ b/kernel/sched/isolation.c > @@ -123,6 +123,8 @@ int housekeeping_update(struct cpumask *isol_mask) > struct cpumask *trial, *old = NULL; > int err; > > + lockdep_assert_cpus_held(); > + > trial = kmalloc(cpumask_size(), GFP_KERNEL); > if (!trial) > return -ENOMEM; > @@ -134,7 +136,7 @@ int housekeeping_update(struct cpumask *isol_mask) > } > > if (!housekeeping.flags) > - static_branch_enable(&housekeeping_overridden); > + static_branch_enable_cpuslocked(&housekeeping_overridden); > > if (housekeeping.flags & HK_FLAG_DOMAIN) > old = housekeeping_cpumask_dereference(HK_TYPE_DOMAIN); Good catch. Thanks, Longman