[PATCH 10/16] sched: optimize __set_cpus_allowed_ptr_locked()

Yury Norov
2022-07-18T19:29:17Z

Don't call cpumask_subset(new_mask, cpu_allowed_mask) if new_mask
is cpu_allowed_mask.

Caught with CONFIG_DEBUG_BITMAP:
[ 0.132174] Call trace:
[ 0.132189] __bitmap_check_params+0x144/0x250
[ 0.132216] __set_cpus_allowed_ptr_locked+0x8c/0x2c0
[ 0.132241] sched_init_smp+0x80/0xd8
[ 0.132273] kernel_init_freeable+0x12c/0x28c
[ 0.132299] kernel_init+0x28/0x13c
[ 0.132325] ret_from_fork+0x10/0x20
[ 0.132354] ---[ end trace 0000000000000000 ]---
[ 0.132378] b1: ffffcd0c07819a58
[ 0.132388] b2: ffffcd0c07819a58
[ 0.132397] b3: 0
[ 0.132405] nbits: 256
[ 0.132414] start: 0
[ 0.132422] off: 0
[ 0.132444] Bitmap: parameters check failed
[ 0.132467] include/linux/bitmap.h [468]: bitmap_subset

Signed-off-by: Yury Norov <yury.norov@gmail.com>
---
kernel/sched/core.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index da0bf6fe9ecd..d6424336ef2d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2874,7 +2874,8 @@ static int __set_cpus_allowed_ptr_locked(struct task_struct *p,
cpu_valid_mask = cpu_online_mask;
}

- if (!kthread && !cpumask_subset(new_mask, cpu_allowed_mask)) {
+ if (!kthread && new_mask != cpu_allowed_mask &&
+ !cpumask_subset(new_mask, cpu_allowed_mask)) {
ret = -EINVAL;
goto out;
}
--
2.34.1