[PATCH] atomic: Specify natural alignment for atomic_t

[Finn Thain]

Some recent commits incorrectly assumed the natural alignment of locks.
That assumption fails on Linux/m68k (and, interestingly, would have failed
on Linux/cris also). This leads to spurious warnings from the hang check
code. Fix this bug by adding the necessary 'aligned' attribute.

Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Cc: Lance Yang <lance.yang@xxxxxxxxx>
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Eero Tamminen <oak@xxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Eero Tamminen <oak@xxxxxxxxxxxxxx>
Closes: https://lore.kernel.org/lkml/CAMuHMdW7Ab13DdGs2acMQcix5ObJK0O2dG_Fxzr8_g58Rc1_0g@xxxxxxxxxxxxxx/
Fixes: e711faaafbe5 ("hung_task: replace blocker_mutex with encoded blocker")
Signed-off-by: Finn Thain <fthain@xxxxxxxxxxxxxx>
---
I tested this on m68k using GCC and it fixed the problem for me. AFAIK,
the other architectures naturally align ints already so I'm expecting to
see no effect there.
---
 include/linux/types.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/types.h b/include/linux/types.h
index 6dfdb8e8e4c3..cd5b2b0f4b02 100644
--- a/include/linux/types.h
+++ b/include/linux/types.h
@@ -179,7 +179,7 @@ typedef phys_addr_t resource_size_t;
 typedef unsigned long irq_hw_number_t;
 
 typedef struct {
-	int counter;
+	int counter __aligned(sizeof(int));
 } atomic_t;
 
 #define ATOMIC_INIT(i) { (i) }
-- 
2.49.1