kernel_optimize_test/fs/pstore
Rob Herring 7ae9cb8193 pstore-ram: Fix hangs by using write-combine mappings
Currently trying to use pstore on at least ARMs can hang as we're
mapping the peristent RAM with pgprot_noncached().

On ARMs, pgprot_noncached() will actually make the memory strongly
ordered, and as the atomic operations pstore uses are implementation
defined for strongly ordered memory, they may not work. So basically
atomic operations have undefined behavior on ARM for device or strongly
ordered memory types.

Let's fix the issue by using write-combine variants for mappings. This
corresponds to normal, non-cacheable memory on ARM. For many other
architectures, this change does not change the mapping type as by
default we have:

#define pgprot_writecombine pgprot_noncached

The reason why pgprot_noncached() was originaly used for pstore
is because Colin Cross <ccross@android.com> had observed lost
debug prints right before a device hanging write operation on some
systems. For the platforms supporting pgprot_noncached(), we can
add a an optional configuration option to support that. But let's
get pstore working first before adding new features.

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Anton Vorontsov <cbouatmailru@gmail.com>
Cc: Colin Cross <ccross@android.com>
Cc: Olof Johansson <olof@lixom.net>
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Rob Herring <rob.herring@calxeda.com>
[tony@atomide.com: updated description]
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2014-12-11 13:35:49 -08:00
..
ftrace.c pstore: Add hsize argument in write_buf call of pstore_ftrace_call 2013-07-02 18:39:37 +10:00
inode.c pstore: Honor dmesg_restrict sysctl on dmesg dumps 2014-11-05 09:59:48 -08:00
internal.h pstore: Add file extension to pstore file if compressed 2013-08-19 11:53:27 -07:00
Kconfig pstore/Kconfig: Select ZLIB_DEFLATE and ZLIB_INFLATE when PSTORE is selected 2013-08-19 10:18:10 -07:00
Makefile pstore: Add persistent function tracing 2012-07-17 10:05:52 -07:00
platform.c fs/pstore: logging clean-up 2014-06-06 16:08:13 -07:00
ram_core.c pstore-ram: Fix hangs by using write-combine mappings 2014-12-11 13:35:49 -08:00
ram.c pstore/ram: Strip ramoops header for correct decompression 2014-11-05 09:58:17 -08:00