From mboxrd@z Thu Jan 1 00:00:00 1970 From: robherring2@gmail.com (Rob Herring) Date: Wed, 10 Apr 2013 10:55:35 -0500 Subject: [RFC PATCH 3/3] pstore/ram: avoid atomic accesses for ioremapped regions In-Reply-To: References: <1365563297-12480-1-git-send-email-robherring2@gmail.com> <1365563297-12480-3-git-send-email-robherring2@gmail.com> Message-ID: <51658B77.4050400@gmail.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 04/09/2013 11:10 PM, Colin Cross wrote: > On Tue, Apr 9, 2013 at 8:08 PM, Rob Herring wrote: >> From: Rob Herring >> >> 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