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McKenney" , Arnd Bergmann , Boqun Feng Subject: [PATCH 6/9] locking/lockdep: Avoid struct return in lock_stats() Date: Wed, 16 Jul 2025 07:48:15 -0700 Message-Id: <20250716144818.47650-7-boqun.feng@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) In-Reply-To: <20250716144818.47650-1-boqun.feng@gmail.com> References: <20250716144818.47650-1-boqun.feng@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Arnd Bergmann 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 lim= it (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: Arnd Bergmann Signed-off-by: Boqun Feng Link: https://lore.kernel.org/r/20250610092941.2642847-1-arnd@kernel.org --- include/linux/lockdep_types.h | 2 +- kernel/locking/lockdep.c | 27 ++++++++++++--------------- kernel/locking/lockdep_proc.c | 2 +- 3 files changed, 14 insertions(+), 17 deletions(-) diff --git a/include/linux/lockdep_types.h b/include/linux/lockdep_types.h index 9f361d3ab9d9..eae115a26488 100644 --- a/include/linux/lockdep_types.h +++ b/include/linux/lockdep_types.h @@ -175,7 +175,7 @@ struct lock_class_stats { unsigned long bounces[nr_bounce_types]; }; =20 -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 =20 diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index dd2bbf73718b..0c941418a215 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -297,33 +297,30 @@ static inline void lock_time_add(struct lock_time *sr= c, struct lock_time *dst) dst->nr +=3D src->nr; } =20 -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; =20 - 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 =3D &per_cpu(cpu_lock_stats, cpu)[class - lock_classes]; =20 - for (i =3D 0; i < ARRAY_SIZE(stats.contention_point); i++) - stats.contention_point[i] +=3D pcs->contention_point[i]; + for (i =3D 0; i < ARRAY_SIZE(stats->contention_point); i++) + stats->contention_point[i] +=3D pcs->contention_point[i]; =20 - for (i =3D 0; i < ARRAY_SIZE(stats.contending_point); i++) - stats.contending_point[i] +=3D pcs->contending_point[i]; + for (i =3D 0; i < ARRAY_SIZE(stats->contending_point); i++) + stats->contending_point[i] +=3D pcs->contending_point[i]; =20 - 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); =20 - 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); =20 - for (i =3D 0; i < ARRAY_SIZE(stats.bounces); i++) - stats.bounces[i] +=3D pcs->bounces[i]; + for (i =3D 0; i < ARRAY_SIZE(stats->bounces); i++) + stats->bounces[i] +=3D pcs->bounces[i]; } - - return stats; } =20 void clear_lock_stats(struct lock_class *class) diff --git a/kernel/locking/lockdep_proc.c b/kernel/locking/lockdep_proc.c index b52c07c4707c..1916db9aa46b 100644 --- a/kernel/locking/lockdep_proc.c +++ b/kernel/locking/lockdep_proc.c @@ -657,7 +657,7 @@ static int lock_stat_open(struct inode *inode, struct f= ile *file) if (!test_bit(idx, lock_classes_in_use)) continue; iter->class =3D class; - iter->stats =3D lock_stats(class); + lock_stats(class, &iter->stats); iter++; } =20 --=20 2.39.5 (Apple Git-154)