Hi! > Currently, if a task is stopped (ie. it's in the TASK_STOPPED state), it is > considered by the freezer as unfreezeable. However, there may be a race > between the freezer and the delivery of the continuation signal to the task > resulting in the task running after we have finished freezing other tasks. > This, in turn, may lead to undesirable effects up to and including a > corruption of data. > > To prevent this from happening we first need to make the freezer consider > stopped tasks as freezeable. For this purpose we need to make freezeable() > stop returning 0 for these tasks. We must remember, however, that the > stopped tasks need not receive the continuation signal before thaw_processes() > is called, so as soon as PF_FREEZE is set for them try_to_freeze_tasks() > should stop counting them as the ones to wait for. Additionally, if there's a > traced task (ie. a task in the TASK_TRACED state) the parent of which has > PF_FREEZE set and is stopped, try_to_freeze_tasks() should not wait for it. > Moreover, if there are some stopped tasks that haven't received the continuation > signal before thaw_processes() is called, we must clear PF_FREEZE for them so > that they don't go to the refrigerator when it's no longer desirable. > > Still if a stopped tasks receives the continuation signal after the freezer > has returned, it should immediately go to the refrigerator. For this reason > we need to place the call to try_to_freeze() in get_signal_to_deliver() right > after the relock label. > > It is also reasonable to change the error paths so that the names of stopped > or traced tasks which have not frozen are not reported to the user, because in > the majority of cases they would be false positives. > > Signed-off-by: Rafael J. Wysocki <rjw at sisk.pl> Okay, lets go ahead with this one. (ACK) I still think we should be able to find some simpler solution, I'll take a look. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
