Messages in this thread | | | Date | Sat, 3 Mar 2007 20:32:40 +0300 | From | Oleg Nesterov <> | Subject | Re: [PATCH -mm 3/7] Freezer: Remove PF_NOFREEZE from rcutorture thread |
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On 03/02, Paul E. McKenney wrote: > > On Sat, Mar 03, 2007 at 02:33:37AM +0300, Oleg Nesterov wrote: > > On 03/02, Paul E. McKenney wrote: > > > > > > One way to embed try_to_freeze() into kthread_should_stop() might be > > > as follows: > > > > > > int kthread_should_stop(void) > > > { > > > if (kthread_stop_info.k == current) > > > return 1; > > > try_to_freeze(); > > > return 0; > > > } > > > > I think this is dangerous. For example, worker_thread() will probably > > need some special actions after return from refrigerator. Also, a kernel > > thread may check kthread_should_stop() in the place where try_to_freeze() > > is not safe. > > > > Perhaps we should introduce a new helper which does this. > > Good point -- the return value from try_to_freeze() is lost if one uses > the above approach. About one third of the calls to try_to_freeze() > in 2.6.20 pay attention to the return value. > > One approach would be to have a kthread_should_stop_nofreeze() for those > cases, and let the default be to try to freeze.
I personally think we should do the opposite, add kthread_should_stop_check_freeze() or something. kthread_should_stop() is like signal_pending(), we can use it under spin_lock (and it is probably used this way by some out-of-tree driver). The new helper is obviously "might_sleep()".
Oleg.
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