netdev - [PATCH 09/16] irq: don't copy cpu affinity mask if source is equal to destination

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Date:   Mon, 18 Jul 2022 12:28:37 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     linux-kernel@...r.kernel.org,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Alexey Klimov <aklimov@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Ben Segall <bsegall@...gle.com>,
        Christoph Lameter <cl@...ux.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Dennis Zhou <dennis@...nel.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Eric Dumazet <edumazet@...gle.com>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Ingo Molnar <mingo@...hat.com>,
        Isabella Basso <isabbasso@...eup.net>,
        John Fastabend <john.fastabend@...il.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Juergen Gross <jgross@...e.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        KP Singh <kpsingh@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Martin KaFai Lau <kafai@...com>,
        Mel Gorman <mgorman@...e.de>, Miroslav Benes <mbenes@...e.cz>,
        Nathan Chancellor <nathan@...nel.org>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Song Liu <songliubraving@...com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Tejun Heo <tj@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Valentin Schneider <vschneid@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Vlastimil Babka <vbabka@...e.cz>, Yonghong Song <yhs@...com>,
        Yury Norov <yury.norov@...il.com>, linux-mm@...ck.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: [PATCH 09/16] irq: don't copy cpu affinity mask if source is equal to destination

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@...il.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