On 02/16, Srivatsa Vaddagiri wrote: > > On Wed, Feb 14, 2007 at 11:22:09PM +0300, Oleg Nesterov wrote: > > > o Splits CPU_DEAD into two events namely > > > - CPU_DEAD: which will be handled while the processes are still > > > frozen. > > > > > > - CPU_DEAD_KILL_THREADS: To be handled after we thaw_processes. > > > > > > Imho, this is not right. This change the meaning of CPU_DEAD, and so > > we should fix all users of CPU_DEAD as well. > > Why should we fix all users? Only users who were doing a kthread_stop() > in CPU_DEAD need to be fixed. From my count, only 5 users (out of a > total of 35) need to be fixed to not do kthread_stop in CPU_DEAD.
But still we need to fix or at least check them, > > How about > > > > CPU_DEAD_WHATEVER > > the processes are still frozen > > > > CPU_DEAD > > after we thaw_processes > > > > This way we can add processing of the new CPU_DEAD_WHATEVER event where > > it may help. > > Well, -most- of the work needs to be done in a state when processes are > frozen. The only exception is cleaning up of per-cpu threads (which is > not possible with processes frozen - if we can find a way to make that > possible, then everything can be done in CPU_DEAD). > > If we go by the change suggested above, then we need to fix all users of > CPU_DEAD Sorry, I can't understand you. This patch adds the new state, why should we fix all users of CPU_DEAD if they were correct? CPU_DEAD retains its old meaning, all users should work as before? > to do what they are doing in CPU_DEAD_WHATEVER (when processes > are frozen). We don't have such users! because we don't have CPU_DEAD_WHATEVER yet. IOW: I think this new state should have a new name, CPU_DEAD should continue to be called as a last step. Then we can teach cpu callback's to to take an advantage of CPU_DEAD_WHATEVER, and we can do this in a separate patches. No? > > CPU_UP_PREPARE is called after freeze_processes()... Probably this works, > > but imho this is no good. Suppose for a moment that khelper will be frozen > > (yes, yes it can't be), then we can't do kthread_create(). > > Yes, I am worried about doing so many things with processes frozen. > Maybe time (and more testing) will tell us if this is a bad thing or > not. The only dependency I have found so far is that kthread workqueue needs > to > be up (and hence its worker thread needs to be exempted from hotplug > freeze). We should mark kthread workqueue accordingly as not freezable > for hotplug. Yes, this is what I was talking about. 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/
