Commit a49e4629 authored by Prateek Sood's avatar Prateek Sood Committed by Tejun Heo
Browse files

cpuset: Make cpuset hotplug synchronous 



Convert cpuset_hotplug_workfn() into synchronous call for cpu hotplug
path. For memory hotplug path it still gets queued as a work item.

Since cpuset_hotplug_workfn() can be made synchronous for cpu hotplug
path, it is not required to wait for cpuset hotplug while thawing
processes.

Signed-off-by: default avatarPrateek Sood <prsood@codeaurora.org>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 3010c5b9

include/linux/cpuset.h

+0 −3
Original line number Diff line number Diff line
@@ -54,7 +54,6 @@ extern int cpuset_init(void); 
extern void cpuset_init_smp(void);

extern void cpuset_force_rebuild(void);

extern void cpuset_update_active_cpus(void);

extern void cpuset_wait_for_hotplug(void);

extern void cpuset_read_lock(void);

extern void cpuset_read_unlock(void);

extern void cpuset_cpus_allowed(struct task_struct *p, struct cpumask *mask);
@@ -176,8 +175,6 @@ static inline void cpuset_update_active_cpus(void) 
	partition_sched_domains(1, NULL, NULL);

}



static inline void cpuset_wait_for_hotplug(void) { }



static inline void cpuset_read_lock(void) { }

static inline void cpuset_read_unlock(void) { }

kernel/cgroup/cpuset.c

+19 −12
Original line number Diff line number Diff line
@@ -3101,7 +3101,7 @@ update_tasks: 
}



/**

 * cpuset_hotplug_workfn - handle CPU/memory hotunplug for a cpuset

 * cpuset_hotplug - handle CPU/memory hotunplug for a cpuset

 *

 * This function is called after either CPU or memory configuration has

 * changed and updates cpuset accordingly.  The top_cpuset is always
@@ -3116,7 +3116,7 @@ update_tasks: 
 * Note that CPU offlining during suspend is ignored.  We don't modify

 * cpusets across suspend/resume cycles at all.

 */

static void cpuset_hotplug_workfn(struct work_struct *work)

static void cpuset_hotplug(bool use_cpu_hp_lock)

{

	static cpumask_t new_cpus;

	static nodemask_t new_mems;
@@ -3201,25 +3201,32 @@ static void cpuset_hotplug_workfn(struct work_struct *work) 
	/* rebuild sched domains if cpus_allowed has changed */

	if (cpus_updated || force_rebuild) {

		force_rebuild = false;

		if (use_cpu_hp_lock)

			rebuild_sched_domains();

		else {

			/* Acquiring cpu_hotplug_lock is not required.

			 * When cpuset_hotplug() is called in hotplug path,

			 * cpu_hotplug_lock is held by the hotplug context

			 * which is waiting for cpuhp_thread_fun to indicate

			 * completion of callback.

			*/

			percpu_down_write(&cpuset_rwsem);

			rebuild_sched_domains_locked();

			percpu_up_write(&cpuset_rwsem);

		}

	}



	free_cpumasks(NULL, ptmp);

}



void cpuset_update_active_cpus(void)

static void cpuset_hotplug_workfn(struct work_struct *work)

{

	/*

	 * We're inside cpu hotplug critical region which usually nests

	 * inside cgroup synchronization.  Bounce actual hotplug processing

	 * to a work item to avoid reverse locking order.

	 */

	schedule_work(&cpuset_hotplug_work);

	cpuset_hotplug(true);

}



void cpuset_wait_for_hotplug(void)

void cpuset_update_active_cpus(void)

{

	flush_work(&cpuset_hotplug_work);

	cpuset_hotplug(false);

}



/*

kernel/power/process.c

+0 −2
Original line number Diff line number Diff line
@@ -204,8 +204,6 @@ void thaw_processes(void) 
	__usermodehelper_set_disable_depth(UMH_FREEZING);

	thaw_workqueues();



	cpuset_wait_for_hotplug();



	read_lock(&tasklist_lock);

	for_each_process_thread(g, p) {

		/* No other threads should have PF_SUSPEND_TASK set */

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