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authorTejun Heo <tj@kernel.org>2020-04-03 11:32:13 -0400
committerTejun Heo <tj@kernel.org>2020-04-03 11:32:13 -0400
commit2b729fe7f3e9478a21a336231daf35768e7cf37b (patch)
tree46637b3b2e958100d505c86e2a43a65ccb4eefd4 /kernel
parent38aca3071cebc90e6b07abd697cba5c9d7b37a94 (diff)
downloadlinux-2b729fe7f3e9478a21a336231daf35768e7cf37b.tar.bz2
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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/cgroup/cpuset.c31
-rw-r--r--kernel/power/process.c2
2 files changed, 14 insertions, 19 deletions
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 */