On 2014/2/27 18:19, Li Zefan wrote: > I can trigger a lockdep warning: > > # mount -t cgroup -o cpuset xxx /cgroup > # mkdir /cgroup/cpuset > # mkdir /cgroup/tmp > # echo 0 > /cgroup/tmp/cpuset.cpus > # echo 0 > /cgroup/tmp/cpuset.mems > # echo 1 > /cgroup/tmp/cpuset.memory_migrate > # echo $$ > /cgroup/tmp/tasks > # echo 1 > /cgruop/tmp/cpuset.mems > > =============================== > [ INFO: suspicious RCU usage. ] > 3.14.0-rc1-0.1-default+ #32 Not tainted > ------------------------------- > include/linux/cgroup.h:682 suspicious rcu_dereference_check() usage! > ... > [<ffffffff81582174>] dump_stack+0x72/0x86 > [<ffffffff810b8f01>] lockdep_rcu_suspicious+0x101/0x140 > [<ffffffff81105ba1>] cpuset_migrate_mm+0xb1/0xe0 > ... > > We used to hold cgroup_mutex when calling cpuset_migrate_mm(), but now > we hold cpuset_mutex, which causes task_css() to complain. > > This is not a false-positive but a real issue. > > Holding cpuset_mutex won't prevent a task's cpuset from changing, and I meant it won't prevent a task from migrating to another cpuset. > it won't prevent the original task->cgroup from destroying during this > change. -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
