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Revert "cpuset: Make cpuset hotplug synchronous" 

This reverts commit a49e4629b5 ("cpuset: Make cpuset hotplug synchronous") as
it may deadlock with cpu hotplug path.

Link: http://lkml.kernel.org/r/F0388D99-84D7-453B-9B6B-EEFF0E7BE4CC@lca.pw
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Qian Cai <cai@lca.pw>
Cc: Prateek Sood <prsood@codeaurora.org>
This commit is contained in:
Tejun Heo 2020-04-03 11:32:13 -04:00
parent 38aca3071c
commit 2b729fe7f3
3 changed files with 19 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
include/linux/cpuset.h
View File

@ -54,6 +54,7 @@ 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);
@ -175,6 +176,8 @@ 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) { }

35
kernel/cgroup/cpuset.c
View File

@ -3101,7 +3101,7 @@ update_tasks:
}
/**
* cpuset_hotplug - handle CPU/memory hotunplug for a cpuset
* cpuset_hotplug_workfn - 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(bool use_cpu_hp_lock)
static void cpuset_hotplug_workfn(struct work_struct *work)
{
static cpumask_t new_cpus;
static nodemask_t new_mems;
@ -3201,32 +3201,25 @@ static void cpuset_hotplug(bool use_cpu_hp_lock)
/* 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);
}
rebuild_sched_domains();
}
free_cpumasks(NULL, ptmp);
}
static void cpuset_hotplug_workfn(struct work_struct *work)
{
cpuset_hotplug(true);
}
void cpuset_update_active_cpus(void)
{
cpuset_hotplug(false);
/*
* 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);
}
void cpuset_wait_for_hotplug(void)
{
flush_work(&cpuset_hotplug_work);
}
/*

2
kernel/power/process.c
View File

@ -204,6 +204,8 @@ 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 */