[PATCH] pstore/core: drop cmpxchg based updates

On Wed, Aug 24, 2016 at 03:09:35PM +0200, Sebastian Andrzej Siewior wrote:

I have here a FPGA behind PCIe which exports SRAM which I use for
pstore. Now it seems that the FPGA no longer supports cmpxchg based
updates and writes back 0xff?ff and returns the same.  This leads to
crash during crash rendering pstore useless.
Since I doubt that there is much benefit from using cmpxchg() here, I am
dropping this atomic access and use the spinlock based version.

Cc: Anton Vorontsov <redacted>
Cc: Colin Cross <redacted>
Cc: Kees Cook <redacted>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Tested-by: Rabin Vincent <redacted>

This patch is needed for pstore to work on (most?) ARMv7 chips.  See
this thread for details:
https://lkml.kernel.org/g/CABXOdTfT7xMfiBvRuUS1hsVs=q5q2wY1x1Z8oCyyJNFckM0g0A at mail.gmail.com