arm64: stacktrace: use non-atomic __set_bit

Use the non-atomic version of set_bit() in arch/arm64/kernel/stacktrace.c,
as there is no concurrent accesses to frame->prev_type.

This speeds up stack trace collection and improves the boot time of
Generic KASAN by 2-5%.

Suggested-by: Mark Rutland <[email protected]>
Acked-by: Mark Rutland <[email protected]>
Signed-off-by: Andrey Konovalov <[email protected]>
Link: https://lore.kernel.org/r/23dfa36d1cc91e4a1059945b7834eac22fb9854d.1653317461.git.andreyknvl@google.com
Signed-off-by: Will Deacon <[email protected]>

Author: xairy

arch/arm64/kernel/stacktrace.c

@@ -117,7 +117,7 @@ static int notrace unwind_next(struct task_struct *tsk,
 		if (fp <= state->prev_fp)
 			return -EINVAL;
 	} else {
-		set_bit(state->prev_type, state->stacks_done);
+		__set_bit(state->prev_type, state->stacks_done);
 	}
 
 	/*