On 06/14, Rafael J. Wysocki wrote: > > Sorry for being late, I've just realized that you are discussing the freezer > here. ;-)
my fault, I was going to cc you but forgot, sorry! > On Wednesday, 13 June 2007 17:15, Oleg Nesterov wrote: > > > > @@ -105,7 +105,11 @@ static int recalc_sigpending_tsk(struct > > > set_tsk_thread_flag(t, TIF_SIGPENDING); > > > return 1; > > > } > > > - clear_tsk_thread_flag(t, TIF_SIGPENDING); > > > + /* > > > + * We must never clear the flag in another thread, or in current > > > + * when it's possible the current syscall is returning -ERESTART*. > > > + * So we don't clear it here, and only callers who know they should do. > > > + */ > > > return 0; > > > } > > > > This breaks cancel_freezing(). Somehow we should clear TIF_SIGPENDING for > > kernel threads. Otherwise we may have subtle failures if > > try_to_freeze_tasks() > > fails. > > Well, the only code path in which we'd want to call cancel_freezing() for > kernel > threads is when the freezing of kernel threads. However, this only happens if > one of the kernel threads declares itself as freezable and the fails to call > try_to_freeze(), which is a bug. But this happens? We know a lot of reasons why try_to_freeze() can fail just because some kthread waits for already frozen task. > Thus I don't think that we need to worry > about that case too much. Well, we can have very subtle problems because a kernel thread may run with TIF_SIGPENDING forever. This means in particualar that any wait_event_interruptible() can't succeed. I think this is worse than explicit failure (like -ERESSTART... leak), because it is hard to reproduce/debug. > Moreover, I'm not sure that it's a good idea at all to send signals to kernel > threads from the freezer, since in fact we only need to wake them up to make > them call try_to_freeze() (after we've set TIF_FREEZE for them). Yes! I completely agree. Oleg. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
