Messages in this thread Patch in this message | | | Date | Wed, 21 Dec 2011 18:56:35 +0100 | From | Frederic Weisbecker <> | Subject | Re: Q: cgroup: Questions about possible issues in cgroup locking |
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On Wed, Dec 21, 2011 at 02:08:48PM +0100, Oleg Nesterov wrote: > On 12/21, Frederic Weisbecker wrote: > > Hi, > > > > Starring at some parts of cgroups, I have a few questions: > > > > - Is cgroup_enable_task_cg_list()'s while_each_thread() safe > > against concurrent exec()? The leader may change in de_thread() > > and invalidate the test done in while_each_thread(). > > Yes. Oh, we need to do something with while_each_thread.
Would something like this work?
diff --git a/include/linux/sched.h b/include/linux/sched.h index c0c5876..e002a00 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2293,8 +2293,12 @@ extern bool current_is_single_threaded(void); #define do_each_thread(g, t) \ for (g = t = &init_task ; (g = t = next_task(g)) != &init_task ; ) do -#define while_each_thread(g, t) \ - while ((t = next_thread(t)) != g) +#define while_each_thread(g, t) \ + while (({ \ + struct task_struct *__prev = t; \ + t = next_thread(t); \ + t != __prev && t != g; \ + })) static inline int get_nr_threads(struct task_struct *tsk) {
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