Re: pstore dump inside an nmi handler

[Matthew Garrett]

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.

EFI can't sleep (at least, not as far as the kernel's concerned), so 
we're safe there. I think it's fair to assume atomicity here - crash 
dumping is a pretty specific situation. Although we may need to think 
about whether pstore should be saving reboot and poweroff in that case.

-- 
Matthew Garrett | mjg59@xxxxxxxxxxxxx
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