Hi. On Tuesday 31 January 2006 08:25, Pavel Machek wrote: > On Po 30-01-06 23:18:28, Rafael J. Wysocki wrote: > > Hi, > > > > On Thursday 26 January 2006 04:45, Nigel Cunningham wrote: > > > Add a helper which counts the number of patches of a type (all > > > or userspace only) which are in TASK_UNINTERRUPTIBLE state. > > > These tasks are signalled (just in case they leave that state at > > > a later point), but we do not consider freezing to have failed > > > if and when they do not enter the freezer. > > > > > > Note that when they eventually leave TASK_UNINTERRUPTIBLE state, > > > they will enter the refrigerator, but will immediately exit if > > > we no longer want to freeze at that point. > > > > I think we need to do something like this to prevent problems with > > freezing under load. > > That is dangerous... task in UNINTERRUPTIBLE may hold some lock, > AFAICT. > > No, there's some simple bug in refrigerator, and I/we need to fix > that. Signals work under load, so refrigerator should, too. I know you understand English, Pavel! Re-read what I wrote previously! The problem is a race. You're telling processes that process I/O to freeze at the same time as you're telling processes that submit I/O to freeze. If kjournald (eg) enters the refrigerator while dd is still running, dd is going to have a chance of getting stuck, waiting for some I/O to complete. This also means your sys_sync is totally useless if anything is submitting I/O, since there will still be I/O being submitted after the sync is done. This is why (in the numbers I submitted yesterday), the current implementation took so much longer than the new one. The sys_sync really only introduces a big delay. It needs to be done after the things that generate I/O have been stopped. Regards, Nigel -- See our web page for Howtos, FAQs, the Wiki and mailing list info. http://www.suspend2.net IRC: #suspend2 on Freenode
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- Re: [ 15/23] [Suspend2] Helper for counting uninterruptible threads of a type.
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