[RFC PATCH 3/3] pstore/ram: avoid atomic accesses for ioremapped regions

[Rob Herring]

On 04/09/2013 11:10 PM, Colin Cross wrote:
> On Tue, Apr 9, 2013 at 8:08 PM, Rob Herring <robherring2 at gmail.com> wrote:
>> From: Rob Herring <rob.herring at calxeda.com>
>>
>> For persistent RAM outside of main memory, the memory may have limitations
>> on supported accesses. For internal RAM on highbank platform exclusive
>> accesses are not supported and will hang the system. So atomic_cmpxchg
>> cannot be used. This commit uses spinlock protection for buffer size and
>> start updates on ioremapped regions instead.
> 
> I used atomics in persistent_ram to support persistent ftrace, which
> now exists as PSTORE_FTRACE.  At some point during development I had
> trouble with recursive tracing causing an infinite loop, so you may
> want to test that calling out to spinlock functions with PSTORE_FTRACE
> turned on and enabled doesn't cause a problem.

I've tested that now and it appears to work fine. Was there some
specific setup of ftrace that caused problems?

Rob