On 2021-08-17 11:31:56 [+0200], Vlastimil Babka wrote:

On 8/17/21 11:12 AM, Sebastian Andrzej Siewior wrote:

quoted

On 2021-08-17 10:37:48 [+0200], Vlastimil Babka wrote:

quoted

OK reproduced. Thanks, will investigate.

With the local_lock at the top, the needed alignment gets broken for dbl
cmpxchg.

Right. I wondered why the checks in __pcpu_double_call_return_bool
didn't trigger. They are VM_BUG_ON() so they did trigger after enabling
DEBUG_VM.

Without the right debugging enabled

| typedef struct {
| #ifdef CONFIG_DEBUG_LOCK_ALLOC
|         struct lockdep_map      dep_map;
|         struct task_struct      *owner;
| #endif
| } local_lock_t;

the struct is just empty.

Sebastian