From: Vasant Hegde <vasant.hegde@amd.com>
To: Ankit Soni <Ankit.Soni@amd.com>, iommu@lists.linux.dev
Cc: suravee.suthikulpanit@amd.com, joro@8bytes.org, will@kernel.org,
robin.murphy@arm.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] iommu/amd: move wait_on_sem() out of spinlock
Date: Tue, 2 Dec 2025 10:44:55 +0530 [thread overview]
Message-ID: <7ba57474-57ad-4c81-bb50-4e0c6e3be633@amd.com> (raw)
In-Reply-To: <60d2601b17c7008834fe393e75990371cdac74b5.1764591214.git.Ankit.Soni@amd.com>
On 12/1/2025 8:09 PM, Ankit Soni wrote:
> With iommu.strict=1, the existing completion wait path can cause soft
> lockups under stressed environment, as wait_on_sem() busy-waits under the
> spinlock with interrupts disabled.
>
> Move the completion wait in iommu_completion_wait() out of the spinlock.
> wait_on_sem() only polls the hardware-updated cmd_sem and does not require
> iommu->lock, so holding the lock during the busy wait unnecessarily
> increases contention and extends the time with interrupts disabled.
>
> Signed-off-by: Ankit Soni <Ankit.Soni@amd.com>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
-Vasant
next prev parent reply other threads:[~2025-12-02 5:15 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-01 14:39 Ankit Soni
2025-12-02 5:14 ` Vasant Hegde [this message]
2026-01-10 9:54 ` Jörg Rödel
2026-01-10 14:00 ` Markus Elfring
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