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From: Thomas Gleixner <tglx@kernel.org>
To: Troy Mitchell <troy.mitchell@linux.dev>,
	Anup Patel <anup@brainfault.org>, Radu Rendec <radu@rendec.net>,
	Paul Walmsley <pjw@kernel.org>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Alexandre Ghiti <alex@ghiti.fr>
Cc: Anup Patel <apatel@ventanamicro.com>,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	Troy Mitchell <troy.mitchell@linux.dev>
Subject: Re: [PATCH] irqchip/riscv-aplic: Process pending affinity changes on EOI
Date: Mon, 09 Nov 2026 11:13:41 +0100	[thread overview]
Message-ID: <87pkweuxbe.ffs@fw13> (raw)
In-Reply-To: <20261104-aplic-affinity-fix-v1-1-e538cd76e563@linux.dev>

On Wed, Nov 04 2026 at 14:21, Troy Mitchell wrote:
> IMSIC rejects an affinity change with -EBUSY while a previous vector
> move is still in flight, and the IRQ core then records the new mask as
> pending. The change is meant to be applied by irq_move_irq() in the
> IMSIC irq_ack callback, but APLIC MSI interrupts are handled by
> handle_fasteoi_irq(), which does not call irq_ack.

Which is a bug when the interrupt is edge type.

Edge type interrupts are fire and forget from the device point of
view. So you want handle_edge_irq() for them, which issues the ack()
_before_ the handler is invoked. Otherwise you can lose interrupts.

Thanks,

        tglx

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WARNING: multiple messages have this Message-ID (diff)
From: Thomas Gleixner <tglx@kernel.org>
To: Troy Mitchell <troy.mitchell@linux.dev>,
	Anup Patel <anup@brainfault.org>, Radu Rendec <radu@rendec.net>,
	Paul Walmsley <pjw@kernel.org>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Alexandre Ghiti <alex@ghiti.fr>
Cc: Anup Patel <apatel@ventanamicro.com>,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	Troy Mitchell <troy.mitchell@linux.dev>
Subject: Re: [PATCH] irqchip/riscv-aplic: Process pending affinity changes on EOI
Date: Mon, 09 Nov 2026 11:13:41 +0100	[thread overview]
Message-ID: <87pkweuxbe.ffs@fw13> (raw)
In-Reply-To: <20261104-aplic-affinity-fix-v1-1-e538cd76e563@linux.dev>

On Wed, Nov 04 2026 at 14:21, Troy Mitchell wrote:
> IMSIC rejects an affinity change with -EBUSY while a previous vector
> move is still in flight, and the IRQ core then records the new mask as
> pending. The change is meant to be applied by irq_move_irq() in the
> IMSIC irq_ack callback, but APLIC MSI interrupts are handled by
> handle_fasteoi_irq(), which does not call irq_ack.

Which is a bug when the interrupt is edge type.

Edge type interrupts are fire and forget from the device point of
view. So you want handle_edge_irq() for them, which issues the ack()
_before_ the handler is invoked. Otherwise you can lose interrupts.

Thanks,

        tglx

  reply	other threads:[~2026-11-09 10:13 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-11-04 14:21 [PATCH] irqchip/riscv-aplic: Process pending affinity changes on EOI Troy Mitchell
2026-11-04 14:21 ` Troy Mitchell
2026-11-09 10:13 ` Thomas Gleixner [this message]
2026-11-09 10:13   ` Thomas Gleixner
2026-11-10  7:15   ` Troy Mitchell
2026-11-10  7:15     ` Troy Mitchell

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