在 2022/1/21 20:43, Waiman Long 写道: > On 1/21/22 05:12, Zhang Qiao wrote: >> As previously discussed(https://lkml.org/lkml/2022/1/20/51), >> cpuset_attach() is affected with similar cpu hotplug race, >> as follow scenario: >> >> cpuset_attach() cpu hotplug >> --------------------------- ---------------------- >> down_write(cpuset_rwsem) >> guarantee_online_cpus() // (load cpus_attach) >> sched_cpu_deactivate >> set_cpu_active() >> // will change cpu_active_mask >> set_cpus_allowed_ptr(cpus_attach) >> __set_cpus_allowed_ptr_locked() >> // (if the intersection of cpus_attach and >> cpu_active_mask is empty, will return -EINVAL) >> up_write(cpuset_rwsem) >> >> To avoid races such as described above, protect cpuset_attach() call >> with cpu_hotplug_lock. >> >> Fixes: be367d099270 ("cgroups: let ss->can_attach and ss->attach do whole threadgroups at a time") >> Reported-by: Zhao Gongyi <zhaogongyi@xxxxxxxxxx> >> Signed-off-by: Zhang Qiao <zhangqiao22@xxxxxxxxxx> >> --- >> kernel/cgroup/cpuset.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c >> index dc653ab26e50..0af5725cc1df 100644 >> --- a/kernel/cgroup/cpuset.c >> +++ b/kernel/cgroup/cpuset.c >> @@ -2252,6 +2252,7 @@ static void cpuset_attach(struct cgroup_taskset *tset) >> cgroup_taskset_first(tset, &css); >> cs = css_cs(css); >> >> + cpus_read_lock(); >> percpu_down_write(&cpuset_rwsem); >> >> guarantee_online_mems(cs, &cpuset_attach_nodemask_to); >> @@ -2305,6 +2306,7 @@ static void cpuset_attach(struct cgroup_taskset *tset) >> wake_up(&cpuset_attach_wq); >> >> percpu_up_write(&cpuset_rwsem); >> + cpus_read_unlock(); >> } >> >> /* The various types of files and directories in a cpuset file system */ >> -- >> 2.18.0 > > The locking sequence looks right. > > Acked-by: Waiman Long <longman@xxxxxxxxxx> > Thanks for your review! Regards, Qiao . > .
