> IMO, we need to use task_lock() in container_exit() to avoid this race.
>
> (I think this race already exists in mainline cpuset.c?)
>
> P.S : cpuset.c checks for PF_EXITING twice in attach_task(), while this
> patch seems to be checking only once. Is that fine?
I think the cpuset code is ok, because, as you note, it locks the task,
picks off the cpuset pointer, and then checks a second time that the
task still does not have PF_EXITING set:
In the kernel/cpuset.c code for attach_task():
task_lock(tsk);
oldcs = tsk->cpuset;
/*
* After getting 'oldcs' cpuset ptr, be sure still not exiting.
* If 'oldcs' might be the top_cpuset due to the_top_cpuset_hack
* then fail this attach_task(), to avoid breaking top_cpuset.count.
*/
if (tsk->flags & PF_EXITING) {
task_unlock(tsk);
mutex_unlock(&callback_mutex);
put_task_struct(tsk);
return -ESRCH;
}
--
I won't rest till it's the best ...
Programmer, Linux Scalability
Paul Jackson <pj@xxxxxxx> 1.925.600.0401
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