On 09/05/2017 06:52 PM, Tejun Heo wrote: > 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. >
Thanks for review Tejun I will send updated patch. -- Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc., is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
