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cgroup/cpuset: Introduce cpuset_cpus_allowed_locked() 

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 <longman@redhat.com>
Signed-off-by: Pingfan Liu <piliu@redhat.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: linux-kernel@vger.kernel.org
To: cgroups@vger.kernel.org
Reviewed-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
pull/1354/merge
Pingfan Liu 2025-11-19 17:55:24 +08:00 committed by Tejun Heo
parent a0131c3927
commit 1f38221511
2 changed files with 44 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
include/linux/cpuset.h
View File

@ -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)

51
kernel/cgroup/cpuset.c
View File

@ -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);
}