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cpuset: Make cpuset hotplug synchronous

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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: Prateek Sood <prsood@codeaurora.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Prateek Sood 2020-01-24 20:37:29 +05:30 committed by Tejun Heo
parent 3010c5b9f5
commit a49e4629b5
3 changed files with 19 additions and 17 deletions
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3
include/linux/cpuset.h
View File

@ -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) { }

29
kernel/cgroup/cpuset.c
View File

@ -3101,7 +3101,7 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp)
}
/**
* 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 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp)
* 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);
}
/*

2
kernel/power/process.c
View File

@ -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 */