Hello, On Mon, Sep 05, 2011 at 06:20:12PM +0200, Oleg Nesterov wrote: > Perhaps it is correct... Just I do not understand what it should do. > I thought it is "wait_for_event && do_not_block_freezer". And at first > glance the code looks as if it tries to do this. Say, in the "likely" > case we restart wait_event_interruptible() after refrigerator(). > > But this looks racy. Suppose that freezing() is already false when > try_to_freeze() or __refrigerator() is called. Say, cgroup_freezer does > freeze_task() + __thaw_task(). Why it returns -ERESTARTSYS in this case? It may return -ERESTARTSYS when not strictly necessary but given that it's supposed to trigger restart anyway I don't think it's actually broken (it doesn't break the contract of the wait). Another thing to note is that kthread freezing via cgroup is almost fundamentally broken. With the removal of freezable_with_signal, this shouldn't be an issue anymore although cgroup_freezer still needs to be fixed to account for kthreads for xstate transitions (it currently triggers BUG_ON). > And if it can be used by the userspace thread, then we should probably > do recalc_sigpending() somewhere, otherwise wait_event_freezable() will > always return -ERESTARTSYS after __refrigerator(). Thankfully, currently, all the few users are kthreads. I don't think it makes sense for userland tasks at all. Interruptible sleeps for userland tasks necessiate the ability to return to signal delivery path and restart or abort the current operation. There's no point in using wait_event_freezable() instead of wait_event_interruptible(). Thanks. -- tejun _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
