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From:   Yury Norov <yury.norov@gmail.com>
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Subject: [PATCH 10/16] sched: optimize __set_cpus_allowed_ptr_locked()
Date:   Mon, 18 Jul 2022 12:28:38 -0700
Message-Id: <20220718192844.1805158-11-yury.norov@gmail.com>
In-Reply-To: <20220718192844.1805158-1-yury.norov@gmail.com>
References: <20220718192844.1805158-1-yury.norov@gmail.com>
MIME-Version: 1.0
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Precedence: bulk

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