Re: pstore: change mutex locking to spin_locks

[Matthew Garrett <mjg@redhat.com>]

On Fri, Aug 12, 2011 at 10:54:51AM -0700, Luck, Tony wrote:
> From: Don Zickus <dzickus@redhat.com>
> 
> pstore was using mutex locking to protect read/write access to the
> backend plug-ins.  This causes problems when pstore is executed in
> an NMI context through panic() -> kmsg_dump().
> 
> This patch changes the mutex to a spin_lock_irqsave then also checks to
> see if we are in an NMI context.  If we are in an NMI and can't get the
> lock, just print a message stating that and blow by the locking.
> 
> All this is probably a hack around the bigger locking problem but it
> solves my current situation of trying to sleep in an NMI context.
> 
> Tested by loading the lkdtm module and executing a HARDLOCKUP which
> will cause the machine to panic inside the nmi handler.
> 
> Signed-off-by: Don Zickus <dzickus@redhat.com>
> Signed-off-by: Tony Luck <tony.luck@intel.com>
Acked-by: Matthew Garrett <mjg@redhat.com>

-- 
Matthew Garrett | mjg59@srcf.ucam.org