path: root/fs
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authorRob Herring <robherring2@gmail.com>2014-09-12 11:32:24 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-01-16 06:59:00 -0800
commitaf74a863b9999e4d2f32140a5edc50e3de5e5a66 (patch)
treeac00c1315bd14529e40dce8cd273d16f00fa59f4 /fs
parent9670f1a473dc2ce7620e91445c1fe3d9a275356d (diff)
pstore-ram: Fix hangs by using write-combine mappings
commit 7ae9cb81933515dc7db1aa3c47ef7653717e3090 upstream. 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 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs')
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c
index 59337326e288..50d3dcdd35fb 100644
--- a/fs/pstore/ram_core.c
+++ b/fs/pstore/ram_core.c
@@ -345,7 +345,7 @@ static void *persistent_ram_vmap(phys_addr_t start, size_t size)
page_start = start - offset_in_page(start);
page_count = DIV_ROUND_UP(size + offset_in_page(start), PAGE_SIZE);
- prot = pgprot_noncached(PAGE_KERNEL);
+ prot = pgprot_writecombine(PAGE_KERNEL);
pages = kmalloc(sizeof(struct page *) * page_count, GFP_KERNEL);
if (!pages) {
@@ -372,7 +372,7 @@ static void *persistent_ram_iomap(phys_addr_t start, size_t size)
return NULL;
- return ioremap(start, size);
+ return ioremap_wc(start, size);
static int persistent_ram_buffer_map(phys_addr_t start, phys_addr_t size,