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From: Yury Norov <yury.norov@gmail.com>
To: Thomas Gleixner <tglx@linutronix.de>, linux-kernel@vger.kernel.org
Cc: Yury Norov <yury.norov@gmail.com>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>
Subject: [PATCH 2/4] lib/group_cpus: relax atomicity requirement in grp_spread_init_one()
Date: Wed,  1 Nov 2023 15:58:18 -0700	[thread overview]
Message-ID: <20231101225820.51342-3-yury.norov@gmail.com> (raw)
In-Reply-To: <20231101225820.51342-1-yury.norov@gmail.com>

Because the function is called with cpus_read_lock() held, all the masks
involved are stabilized, and thus any extra atomicity is not required.

Signed-off-by: Yury Norov <yury.norov@gmail.com>
---
 lib/group_cpus.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/lib/group_cpus.c b/lib/group_cpus.c
index aa3f6815bb12..b1e7d9cc9da9 100644
--- a/lib/group_cpus.c
+++ b/lib/group_cpus.c
@@ -24,8 +24,8 @@ static void grp_spread_init_one(struct cpumask *irqmsk, struct cpumask *nmsk,
 		if (cpu >= nr_cpu_ids)
 			return;
 
-		cpumask_clear_cpu(cpu, nmsk);
-		cpumask_set_cpu(cpu, irqmsk);
+		__cpumask_clear_cpu(cpu, nmsk);
+		__cpumask_set_cpu(cpu, irqmsk);
 		cpus_per_grp--;
 
 		/* If the cpu has siblings, use them first */
@@ -34,9 +34,8 @@ static void grp_spread_init_one(struct cpumask *irqmsk, struct cpumask *nmsk,
 			sibl = cpumask_next(sibl, siblmsk);
 			if (sibl >= nr_cpu_ids)
 				break;
-			if (!cpumask_test_and_clear_cpu(sibl, nmsk))
-				continue;
-			cpumask_set_cpu(sibl, irqmsk);
+			__cpumask_clear_cpu(sibl, nmsk);
+			__cpumask_set_cpu(sibl, irqmsk);
 			cpus_per_grp--;
 		}
 	}
-- 
2.39.2


  parent reply	other threads:[~2023-11-01 22:58 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-11-01 22:58 [PATCH 0/4] lib/group_cpus: rework grp_spread_init_one() and make it O(1) Yury Norov
2023-11-01 22:58 ` [PATCH 1/4] cpumask: introduce for_each_cpu_and_from() Yury Norov
2023-11-01 22:58 ` Yury Norov [this message]
2023-11-01 22:58 ` [PATCH 3/4] lib/group_cpus: optimize inner loop in grp_spread_init_one() Yury Norov
2023-11-01 22:58 ` [PATCH 4/4] lib/group_cpus: optimize outer " Yury Norov
2023-12-04 22:01 ` [PATCH 0/4] lib/group_cpus: rework grp_spread_init_one() and make it O(1) Yury Norov

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