Commit d7c36d63 authored by Arnd Bergmann's avatar Arnd Bergmann Committed by Boqun Feng
Browse files

locking/lockdep: Avoid struct return in lock_stats() 



Returning a large structure from the lock_stats() function causes clang
to have multiple copies of it on the stack and copy between them, which
can end up exceeding the frame size warning limit:

kernel/locking/lockdep.c:300:25: error: stack frame size (1464) exceeds limit (1280) in 'lock_stats' [-Werror,-Wframe-larger-than]
  300 | struct lock_class_stats lock_stats(struct lock_class *class)

Change the calling conventions to directly operate on the caller's copy,
which apparently is what gcc does already.

Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
Signed-off-by: default avatarBoqun Feng <boqun.feng@gmail.com>
Link: https://lore.kernel.org/r/20250610092941.2642847-1-arnd@kernel.org
parent f84a15b9

include/linux/lockdep_types.h

+1 −1
Original line number Diff line number Diff line
@@ -175,7 +175,7 @@ struct lock_class_stats { 
	unsigned long			bounces[nr_bounce_types];

};



struct lock_class_stats lock_stats(struct lock_class *class);

void lock_stats(struct lock_class *class, struct lock_class_stats *stats);

void clear_lock_stats(struct lock_class *class);

#endif

kernel/locking/lockdep.c

+12 −15
Original line number Diff line number Diff line
@@ -297,33 +297,30 @@ static inline void lock_time_add(struct lock_time *src, struct lock_time *dst) 
	dst->nr += src->nr;

}



struct lock_class_stats lock_stats(struct lock_class *class)

void lock_stats(struct lock_class *class, struct lock_class_stats *stats)

{

	struct lock_class_stats stats;

	int cpu, i;



	memset(&stats, 0, sizeof(struct lock_class_stats));

	memset(stats, 0, sizeof(struct lock_class_stats));

	for_each_possible_cpu(cpu) {

		struct lock_class_stats *pcs =

			&per_cpu(cpu_lock_stats, cpu)[class - lock_classes];



		for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)

			stats.contention_point[i] += pcs->contention_point[i];

		for (i = 0; i < ARRAY_SIZE(stats->contention_point); i++)

			stats->contention_point[i] += pcs->contention_point[i];



		for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)

			stats.contending_point[i] += pcs->contending_point[i];

		for (i = 0; i < ARRAY_SIZE(stats->contending_point); i++)

			stats->contending_point[i] += pcs->contending_point[i];



		lock_time_add(&pcs->read_waittime, &stats.read_waittime);

		lock_time_add(&pcs->write_waittime, &stats.write_waittime);

		lock_time_add(&pcs->read_waittime, &stats->read_waittime);

		lock_time_add(&pcs->write_waittime, &stats->write_waittime);



		lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);

		lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);

		lock_time_add(&pcs->read_holdtime, &stats->read_holdtime);

		lock_time_add(&pcs->write_holdtime, &stats->write_holdtime);



		for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)

			stats.bounces[i] += pcs->bounces[i];

		for (i = 0; i < ARRAY_SIZE(stats->bounces); i++)

			stats->bounces[i] += pcs->bounces[i];

	}



	return stats;

}



void clear_lock_stats(struct lock_class *class)

kernel/locking/lockdep_proc.c

+1 −1
Original line number Diff line number Diff line
@@ -657,7 +657,7 @@ static int lock_stat_open(struct inode *inode, struct file *file) 
			if (!test_bit(idx, lock_classes_in_use))

				continue;

			iter->class = class;

			iter->stats = lock_stats(class);

			lock_stats(class, &iter->stats);

			iter++;

		}