Messages in this thread | | | Date | Tue, 30 Jan 2007 11:49:40 -0800 | From | "Paul E. McKenney" <> | Subject | Re: Fw: Re: [mm PATCH 4/6] RCU: (now) CPU hotplug |
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On Tue, Jan 30, 2007 at 10:27:18AM -0800, Andrew Morton wrote: > On Tue, 30 Jan 2007 17:44:47 +0100 > "Rafael J. Wysocki" <rjw@sisk.pl> wrote: > > > > I need to look at all uses of PF_NOFREEZE -- as I understand the > > > code, processes marked PF_NOFREEZE will continue running, potentially > > > interfering with the hotplug operation. :-( > > > > > > I will pass my findings on to this list. > > > > Well, I did it some time ago, although not very thoroughly. > > > > AFAICS there are not so many, but one that stands out is the worker threads. > > We needed two of them to actually go to sleep, so now it's possible to create > > a "freezeable workqueue" the worker thread of which will not set PF_NOFREEZE, > > but currently this is only used by XFS. > > Or we can create a variant of freeze_processes which ignores PF_NOFREEZE. > > As I said eariler, we might need to change the freezer code for this > application. In fact we should do so: that sys_sync() call in there is > quite inappropriate, as is, I suppose, the two-pass freeze attempt. As are > the nice printks, come to that. > > Pretty simple stuff though.
And we might need to change some of the processes that currently set PF_NOFREEZE so that they periodically go somewhere that the freezer can find them -- if I remember correctly, at least some of the PF_NOFREEZE tasks were so marked in order to prevent suspend hangs.
Part of what I need to look at. ;-)
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