From 1f382215119a0bc165e766e5bc424b3d3e8dae35 Mon Sep 17 00:00:00 2001 From: Pingfan Liu Date: Wed, 19 Nov 2025 17:55:24 +0800 Subject: [PATCH] cgroup/cpuset: Introduce cpuset_cpus_allowed_locked() MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Chen Ridong Reviewed-by: Waiman Long Signed-off-by: Tejun Heo --- include/linux/cpuset.h | 9 +++++++- kernel/cgroup/cpuset.c | 51 +++++++++++++++++++++++++++++------------- 2 files changed, 44 insertions(+), 16 deletions(-) diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h index 2ddb256187b5..a98d3330385c 100644 --- a/include/linux/cpuset.h +++ b/include/linux/cpuset.h @@ -74,6 +74,7 @@ extern void inc_dl_tasks_cs(struct task_struct *task); 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_locked(struct task_struct *p, struct cpumask *mask); extern void cpuset_cpus_allowed(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); @@ -195,10 +196,16 @@ static inline void dec_dl_tasks_cs(struct task_struct *task) { } static inline void cpuset_lock(void) { } static inline void cpuset_unlock(void) { } +static inline void cpuset_cpus_allowed_locked(struct task_struct *p, + struct cpumask *mask) +{ + cpumask_copy(mask, task_cpu_possible_mask(p)); +} + static inline void cpuset_cpus_allowed(struct task_struct *p, struct cpumask *mask) { - cpumask_copy(mask, task_cpu_possible_mask(p)); + cpuset_cpus_allowed_locked(p, mask); } static inline bool cpuset_cpus_allowed_fallback(struct task_struct *p) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 976bce6e5673..ec8bebc66469 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -4160,24 +4160,13 @@ void __init cpuset_init_smp(void) BUG_ON(!cpuset_migrate_mm_wq); } -/** - * cpuset_cpus_allowed - return cpus_allowed mask from a tasks cpuset. - * @tsk: pointer to task_struct from which to obtain cpuset->cpus_allowed. - * @pmask: pointer to struct cpumask variable to receive cpus_allowed set. - * - * Description: Returns the cpumask_var_t cpus_allowed of the cpuset - * attached to the specified @tsk. Guaranteed to return some non-empty - * subset of cpu_active_mask, even if this means going outside the - * tasks cpuset, except when the task is in the top cpuset. - **/ - -void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask) +/* + * Return cpus_allowed mask from a task's cpuset. + */ +static void __cpuset_cpus_allowed_locked(struct task_struct *tsk, struct cpumask *pmask) { - unsigned long flags; struct cpuset *cs; - spin_lock_irqsave(&callback_lock, flags); - cs = task_cs(tsk); if (cs != &top_cpuset) guarantee_active_cpus(tsk, pmask); @@ -4197,7 +4186,39 @@ void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask) if (!cpumask_intersects(pmask, cpu_active_mask)) cpumask_copy(pmask, possible_mask); } +} +/** + * cpuset_cpus_allowed_locked - return cpus_allowed mask from a task's cpuset. + * @tsk: pointer to task_struct from which to obtain cpuset->cpus_allowed. + * @pmask: pointer to struct cpumask variable to receive cpus_allowed set. + * + * Similir to cpuset_cpus_allowed() except that the caller must have acquired + * cpuset_mutex. + */ +void cpuset_cpus_allowed_locked(struct task_struct *tsk, struct cpumask *pmask) +{ + lockdep_assert_held(&cpuset_mutex); + __cpuset_cpus_allowed_locked(tsk, pmask); +} + +/** + * cpuset_cpus_allowed - return cpus_allowed mask from a task's cpuset. + * @tsk: pointer to task_struct from which to obtain cpuset->cpus_allowed. + * @pmask: pointer to struct cpumask variable to receive cpus_allowed set. + * + * Description: Returns the cpumask_var_t cpus_allowed of the cpuset + * attached to the specified @tsk. Guaranteed to return some non-empty + * subset of cpu_active_mask, even if this means going outside the + * tasks cpuset, except when the task is in the top cpuset. + **/ + +void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask) +{ + unsigned long flags; + + spin_lock_irqsave(&callback_lock, flags); + __cpuset_cpus_allowed_locked(tsk, pmask); spin_unlock_irqrestore(&callback_lock, flags); } -- 2.47.3