Hello, On Thu, Aug 31, 2017 at 06:43:56PM +0530, Prateek Sood wrote: > > 6) cpuset_mutex is acquired by task init:1 and is waiting for cpuhotplug > > lock.
Yeah, this is the problematic one. > > We can reorder the sequence of locks as in the below diff to avoid this > > deadlock. But I am looking for inputs/better solution to fix this deadlock. > > > > --- > > diff --git a/kernel/cpuset.c b/kernel/cpuset.c > > /** > > * update_tasks_cpumask - Update the cpumasks of tasks in the cpuset. > > * @cs: the cpuset in which each task's cpus_allowed mask needs to be > > changed > > @@ -930,7 +946,7 @@ static void update_cpumasks_hier(struct cpuset *cs, > > struct cpumask *new_cpus) > > rcu_read_unlock(); > > > > if (need_rebuild_sched_domains) > > - rebuild_sched_domains_locked(); > > + rebuild_sched_domains_unlocked()(without taking cpuhotplug.lock) > > } > > > > /** > > @@ -1719,6 +1735,7 @@ static ssize_t cpuset_write_resmask(struct > > kernfs_open_file *of, > > + get_online_cpus(); > > mutex_lock(&cpuset_mutex); > > if (!is_cpuset_online(cs)) > > goto out_unlock; > > @@ -1744,6 +1761,7 @@ static ssize_t cpuset_write_resmask(struct > > kernfs_open_file *of, > > mutex_unlock(&cpuset_mutex); > > + put_online_cpus(); > > kernfs_unbreak_active_protection(of->kn); > > css_put(&cs->css); > > flush_workqueue(cpuset_migrate_mm_wq); > > And the patch looks good to me. Can you please format the patch with proper description and sob? Thanks. -- tejun
