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From: Kuan-Wei Chiu <visitorckw@gmail.com>
To: will@kernel.org, joro@8bytes.org, akpm@linux-foundation.org
Cc: robin.murphy@arm.com, nicolinc@nvidia.com, cychu@google.com,
	hhchung@google.com, amitamishra@google.com, marscheng@google.com,
	linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev,
	linux-kernel@vger.kernel.org, jserv@ccns.ncku.edu.tw,
	eleanor15x@gmail.com, Kuan-Wei Chiu <visitorckw@gmail.com>
Subject: [PATCH 1/2] iommu/arm-smmu-v3: Replace sort_nonatomic() with sort()
Date: Thu, 30 Jul 2026 18:12:15 +0000	[thread overview]
Message-ID: <20260730181216.2709088-2-visitorckw@gmail.com> (raw)
In-Reply-To: <20260730181216.2709088-1-visitorckw@gmail.com>

The number of master->num_streams per master device is typically very
small in practice. Sorting this array takes a very small amount of
time, so there is no practical risk of triggering a soft lockup that
would necessitate calling cond_resched() during the sort.

Replace sort_nonatomic() with the standard sort(). Since this is the
only remaining in-tree caller of sort_nonatomic(), this change paves
the way to eventually remove the unused sort_nonatomic() API from the
core library.

Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
---
Build-tested only.

I'm not really familiar with this driver or smmu internals.
Based on my limited knowledge, master->num_streams should be small
enough to safely switch from sort_nonatomic() to sort(), but I could be
wrong. 

Please review carefully and let me know if there are any cases where
num_streams could actually be large enough to cause issues.

 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index a10affb483a4..dcb6be2df95e 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -4047,9 +4047,9 @@ static int arm_smmu_insert_master(struct arm_smmu_device *smmu,
 	}
 
 	/* Put the ids into order for sorted to_merge/to_unref arrays */
-	sort_nonatomic(master->streams, master->num_streams,
-		       sizeof(master->streams[0]), arm_smmu_stream_id_cmp,
-		       NULL);
+	sort(master->streams, master->num_streams,
+	     sizeof(master->streams[0]), arm_smmu_stream_id_cmp,
+	     NULL);
 
 	mutex_lock(&smmu->streams_mutex);
 	for (i = 0; i < fwspec->num_ids; i++) {
-- 
2.55.0.508.g3f0d502094-goog


  reply	other threads:[~2026-07-30 18:12 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-07-30 18:12 [PATCH 0/2] lib/sort: Clean up sort_nonatomic() and sort_r_nonatomic() Kuan-Wei Chiu
2026-07-30 18:12 ` Kuan-Wei Chiu [this message]
2026-07-30 18:12 ` [PATCH 2/2] Revert "lib/sort.c: add _nonatomic() variants with cond_resched()" Kuan-Wei Chiu
2026-07-30 19:32 ` [PATCH 0/2] lib/sort: Clean up sort_nonatomic() and sort_r_nonatomic() Kuan-Wei Chiu

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