linux-kernel - [PATCH 13/16] time: optimize tick_setup

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Date:   Mon, 18 Jul 2022 12:28:41 -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 13/16] time: optimize tick_setup_device()

tick_setup_device() calls cpumask_equal(newdev->cpumask, cpumask)
even if newdev->cpumask == cpumask. Fix it.

Caught with CONFIG_DEBUG_BITMAP:
[    0.070960] Call trace:
[    0.070974]  __bitmap_check_params+0x144/0x250
[    0.071008]  tick_setup_device+0x70/0x1a0
[    0.071040]  tick_check_new_device+0xc0/0x110
[    0.071066]  clockevents_register_device+0x74/0x1c0
[    0.071090]  clockevents_config_and_register+0x2c/0x3c
[    0.071114]  arch_timer_starting_cpu+0x170/0x470
[    0.071147]  cpuhp_invoke_callback+0x104/0x20c
[    0.071180]  cpuhp_invoke_callback_range+0x70/0xf0
[    0.071205]  notify_cpu_starting+0xac/0xcc
[    0.071229]  secondary_start_kernel+0xe4/0x154
[    0.071259]  __secondary_switched+0xa0/0xa4
[    0.071297] ---[ end trace 0000000000000000 ]---
[    0.071328] b1:	ffffa1f27323b890
[    0.071339] b2:	ffffa1f27323b890
[    0.071348] b3:	0
[    0.071356] nbits:	256
[    0.071366] start:	0
[    0.071374] off:	0
[    0.071383] Bitmap: parameters check failed
[    0.071390] include/linux/bitmap.h [419]: bitmap_equal

Signed-off-by: Yury Norov <yury.norov@...il.com>
---
 kernel/time/tick-common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 7205f76f8d10..7b2da8ef09ef 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -255,7 +255,7 @@ static void tick_setup_device(struct tick_device *td,
 	 * When the device is not per cpu, pin the interrupt to the
 	 * current cpu:
 	 */
-	if (!cpumask_equal(newdev->cpumask, cpumask))
+	if (newdev->cpumask != cpumask && !cpumask_equal(newdev->cpumask, cpumask))
 		irq_set_affinity(newdev->irq, cpumask);
 
 	/*
-- 
2.34.1