Messages in this thread | | | Date | Sun, 25 Feb 2007 18:31:20 +0530 | From | "Aneesh Kumar" <> | Subject | Re: [RFC][PATCH 4/7] Freezer: Fix vfork problem |
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On 2/25/07, Pavel Machek <pavel@ucw.cz> wrote: > Hi! > > > Currently try_to_freeze_tasks() has to wait until all of the vforked processes > > exit and for this reason every user can make it fail. To fix this problem > > we can introduce the additional process flag PF_FREEZER_SKIP to be used by tasks > > that do not want to be counted as freezable by the freezer and want to have > > TIF_FREEZE set nevertheless. Then, this flag can be set by tasks using > > sys_vfork() before they call wait_for_completion() and cleared after they have > > woken up and called try_to_freeze(). In case such a task freezes with > > PF_FREEZER_SKIP set, refrigerator() clears this flag for the current task before > > calling frozen_process(current) to avoid having both PF_FREEZER_SKIP and > > PF_FROZEN set at the same time. > > > > Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> > > > @@ -1393,7 +1394,9 @@ long do_fork(unsigned long clone_flags, > > tracehook_report_clone_complete(clone_flags, nr, p); > > > > if (clone_flags & CLONE_VFORK) { > > + freezer_do_not_count(); > > wait_for_completion(&vfork); > > + freezer_count(); > > tracehook_report_vfork_done(p, nr); > > } > > } else { > > All the infrastructure for this...Would it be easier to introduce > > void fastcall __sched wait_for_completion_freezeable(struct completion *x) > { > might_sleep(); > > spin_lock_irq(&x->wait.lock); > if (!x->done) { > DECLARE_WAITQUEUE(wait, current); > > wait.flags |= WQ_FLAG_EXCLUSIVE; > __add_wait_queue_tail(&x->wait, &wait); > do { > __set_current_state(TASK_UNINTERRUPTIBLE); > spin_unlock_irq(&x->wait.lock); > schedule(); > try_to_freeze(); /* HERE */ > spin_lock_irq(&x->wait.lock); > } while (!x->done); > __remove_wait_queue(&x->wait, &wait); > } > x->done--; > spin_unlock_irq(&x->wait.lock); > } > >
I don't see a call to freezer_do_not_count here. Rafel was talking about a similar change but that would involve special cases in refrigerator such as wakeup parent if the process which is going to be frozen have vfork_done set.
if (->vfork_done) { wakeup_parent() }
how about
void fastcall __sched wait_for_completion_freezeable(struct completion *x) { freezer_do_not_count(); wait_for_completion(x); freezer_count(); }
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