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From:   Yury Norov <yury.norov@gmail.com>
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Subject: [PATCH 09/16] irq: don't copy cpu affinity mask if source is equal to destination
Date:   Mon, 18 Jul 2022 12:28:37 -0700
Message-Id: <20220718192844.1805158-10-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

irq_do_set_affinity() may be called with
	mask == irq_data_to_desc()->irq_common_data.affinity

Copying in that case is useless.

Caught with CONFIG_DEBUG_BITMAP:
[    1.089177]  __bitmap_check_params+0x144/0x250
[    1.089238]  irq_do_set_affinity+0x120/0x470
[    1.089298]  irq_startup+0x140/0x16c
[    1.089350]  __setup_irq+0x668/0x760
[    1.089402]  request_threaded_irq+0xe8/0x1b0
[    1.089474]  vp_find_vqs_msix+0x270/0x410
[    1.089532]  vp_find_vqs+0x48/0x1b4
[    1.089584]  vp_modern_find_vqs+0x1c/0x70
[    1.089641]  init_vq+0x2dc/0x34c
[    1.089690]  virtblk_probe+0xdc/0x710
[    1.089745]  virtio_dev_probe+0x19c/0x270
[    1.089802]  really_probe.part.0+0x9c/0x2ac
[    1.089863]  __driver_probe_device+0x98/0x144
[    1.089923]  driver_probe_device+0xac/0x140
[    1.089985]  __driver_attach+0xf8/0x1a0
[    1.090047]  bus_for_each_dev+0x70/0xd0
[    1.090101]  driver_attach+0x24/0x30
[    1.090153]  bus_add_driver+0x150/0x200
[    1.090208]  driver_register+0x78/0x130
[    1.090266]  register_virtio_driver+0x28/0x40
[    1.090329]  virtio_blk_init+0x68/0xa4
[    1.090400]  do_one_initcall+0x50/0x1c0
[    1.090471]  kernel_init_freeable+0x208/0x28c
[    1.090538]  kernel_init+0x28/0x13c
[    1.090590]  ret_from_fork+0x10/0x20
[    1.090642] ---[ end trace 0000000000000000 ]---
[    1.090705] b1:	ffff2ec742b85e18
[    1.090710] b2:	ffff2ec742b85e18
[    1.090715] b3:	0
[    1.090719] nbits:	256
[    1.090723] start:	0
[    1.090727] off:	0

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

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 8c396319d5ac..f9c1b21584ec 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -284,7 +284,8 @@ int irq_do_set_affinity(struct irq_data *data, const struct cpumask *mask,
 	switch (ret) {
 	case IRQ_SET_MASK_OK:
 	case IRQ_SET_MASK_OK_DONE:
-		cpumask_copy(desc->irq_common_data.affinity, mask);
+		if (desc->irq_common_data.affinity != mask)
+			cpumask_copy(desc->irq_common_data.affinity, mask);
 		fallthrough;
 	case IRQ_SET_MASK_OK_NOCOPY:
 		irq_validate_effective_affinity(data);
-- 
2.34.1