diff options
| author | Tejun Heo <tj@kernel.org> | 2020-04-03 11:32:13 -0400 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2020-04-03 11:32:13 -0400 |
| commit | 2b729fe7f3e9478a21a336231daf35768e7cf37b (patch) | |
| tree | 46637b3b2e958100d505c86e2a43a65ccb4eefd4 | |
| parent | 38aca3071cebc90e6b07abd697cba5c9d7b37a94 (diff) | |
Revert "cpuset: Make cpuset hotplug synchronous"
This reverts commit a49e4629b5ed ("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>
| -rw-r--r-- | include/linux/cpuset.h | 3 | ||||
| -rw-r--r-- | kernel/cgroup/cpuset.c | 31 | ||||
| -rw-r--r-- | kernel/power/process.c | 2 |
3 files changed, 17 insertions, 19 deletions
diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h index cede4cb98b78..04c20de66afc 100644 --- a/include/linux/cpuset.h +++ b/include/linux/cpuset.h @@ -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) { } diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index cafd4d2ff882..58f5073acff7 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -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) +void cpuset_update_active_cpus(void) { - cpuset_hotplug(true); + /* + * 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_update_active_cpus(void) +void cpuset_wait_for_hotplug(void) { - cpuset_hotplug(false); + flush_work(&cpuset_hotplug_work); } /* diff --git a/kernel/power/process.c b/kernel/power/process.c index 08f7019357ee..4b6a54da7e65 100644 --- a/kernel/power/process.c +++ b/kernel/power/process.c @@ -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 */ |