On 02/22, Rafael J. Wysocki wrote: > > Okay, below is what I have right now (compilation tested on x86_64): > > This patch fixes the vfork problem by adding the PF_FREEZER_SKIP flag that > can be used by tasks to tell the freezer not to count them as freezeable and > making the vfork parents set this flag before they call wait_for_completion(). > > Secondly, it fixes the race which happens it a task with TIF_FREEZE set is > preempted right before calling frozen_process() in refrigerator() and stays > unforzen until after thaw_tasks() runs and checks its status. For this > purpose > task_lock() is used.
Great! But please be kind to those of us who read the source control history trying to understand the code. Could you make 2 separate patches? > @@ -207,7 +209,7 @@ static void thaw_tasks(int thaw_user_spa > if (is_user_space(p) == !thaw_user_space) > continue; > > - if (!thaw_process(p)) > + if (!thaw_process(p) && !freezer_should_skip(p)) > printk(KERN_WARNING " Strange, %s not stopped\n", This is racy, the warning could be false. We wake up the task, testing its ->flags is not reliable. Damn. PF_FREEZER_SKIP task could be woken before, clear PF_FREEZER_SKIP, but not frozen. We can change freezer_count() to clear PF_FREEZER_SKIP after try_to_freeze(), not before. Now thaw_process() can take PF_FREEZER_SKIP into account and return "true". But this means the task may be PF_FREEZER_SKIP | PF_FROZEN. What if we we call try_to_freeze_tasks() soon after thaw_tasks()? We may hit the task which leaves the refrigerator, but didn't clear PF_FREEZER_SKIP yet. This means that thaw_process() should clear PF_FREEZER_SKIP as well. This is messy :( Any other ideas? In any case we should imho avoid a separate loop for PF_FREEZER_SKIP tasks to just fix debug messages. In fact it can't help anyway. 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/
