Messages in this thread | | | Date | Tue, 12 Jul 2011 11:34:36 -0400 | From | Don Zickus <> | Subject | Re: pstore dump inside an nmi handler |
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On Mon, Jul 11, 2011 at 05:55:41PM -0400, Don Zickus wrote: > On Fri, Jul 08, 2011 at 02:40:13PM -0700, Luck, Tony wrote: > > > Inside pstore_dump(), the first thing it tries to grab is a mutex_lock() > > > (inside an nmi hander). This seems to be the root cause of my problems. > > > > Someone else pointed out that mutex_lock() is a problem here too. They > > wondered whether spin_lock_irqsave() would work - or whether pstore > > backends were allowed to sleep - to which I said I hoped they didn't, > > but wasn't really sure what the future will hold. > > > > So ... ideas (and patches) are most welcome. > > I tested the spin_lock_irqsave thing on my one box where it was failing > and got past my initial problem into kdump. So that is a positive and I > can post the patch for that. Though it probably isn't a complete > solution, it is better than a mutex. > > However, I have been scratching my head at a follow up problem, which is > when I inject an error which produces an NMI->GHES->panic, the error > record doesn't get stored under pstore (or maybe ERST too). I do see the > ERST code follow all the correct steps in storing the kmsg_dump logs into > the ERST table. Just on the reboot, when I mount pstore it isn't there.
Actually, is it expected that the ERST can handle only 8 records? Also if you remove those records with pstore mount under /mnt; 'rm -rf /mnt/dmesg-*', are those records removed immediately or are they cached to be removed later? IOW, if a did a 'rm -rf ..' and then an 'echo c > /proc/sysrq-trigger' immediately after it, would I expect those records to be removed or not? Testing shows they are removed on reboot but the later 'echo c > ..' didn't save any new error records. :-/
Cheers, Don
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