On Mon, 25 Aug 2025 12:03:05 +1000 Finn Thain fthain@linux-m68k.org wrote:
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@linux-foundation.org Cc: Geert Uytterhoeven geert@linux-m68k.org Cc: Lance Yang lance.yang@linux.dev Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Eero Tamminen oak@helsinkinet.fi Cc: Peter Zijlstra peterz@infradead.org Cc: Will Deacon will@kernel.org Cc: stable@vger.kernel.org Reported-by: Eero Tamminen oak@helsinkinet.fi Closes: https://lore.kernel.org/lkml/CAMuHMdW7Ab13DdGs2acMQcix5ObJK0O2dG_Fxzr8_g58Rc... Fixes: e711faaafbe5 ("hung_task: replace blocker_mutex with encoded blocker") Signed-off-by: Finn Thain fthain@linux-m68k.org
This seems good anyway because unaligned atomic memory access sounds insane. So looks good to me.
Reviewed-by: Masami Hiramatsu (Google) mhiramat@kernel.org
Anyway, Lance's patch[1] is still needed. We'd better gracefully ignore if the blocker is not aligned, because hung_task blocker detection is an optional for debugging and not necessary for the kernel operation.
[1] https://lore.kernel.org/all/20250823050036.7748-1-lance.yang@linux.dev/
Thank you,
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