It looks like on most of architectures "data" member of devres struture
gets aligned to 8-byte "unsigned long long" boundary as one may expect:
if we don't explicitly pack a structure then natural alignment
(which matches each member data type) is used.
But at least on 32-bit ARC architecture ABI requires "long long" types
to be aligned by normal 32-bit word. This makes "data" field aligned to
12 bytes. This is still OK as long as we use 32-bit data only.
But once we want to use native atomic64_t type (i.e. when we use special
instructions LLOCKD/SCONDD for accessing 64-bit data) we easily hit
misaligned access exception.
That's because even on CPUs capable of non-aligned data access LL/SC
instructions require strict alignment.
Signed-off-by: Alexey Brodkin <abrodkin@xxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
drivers/base/devres.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/base/devres.c b/drivers/base/devres.c
index f98a097e73f2..35ddc8b66bc9 100644
--- a/drivers/base/devres.c
+++ b/drivers/base/devres.c
@@ -25,7 +25,7 @@ struct devres_node {
struct devres {
struct devres_node node;
/* -- 3 pointers */
- unsigned long long data[]; /* guarantee ull alignment */
+ unsigned long long data[] __aligned(sizeof(unsigned long long));
};
struct devres_group {
--
2.17.1
