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From: "Troy Mitchell" <troy.mitchell@linux.dev>
To: "Thomas Gleixner" <tglx@kernel.org>
Cc: "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>,
	"Anup Patel" <apatel@ventanamicro.com>,
	<linux-riscv@lists.infradead.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] irqchip/riscv-aplic: Process pending affinity changes on EOI
Date: Tue, 10 Nov 2026 07:15:00 +0000	[thread overview]
Message-ID: <DMRCGHS3V729.FIU61TS3JYWD@linux.dev> (raw)
In-Reply-To: <87pkweuxbe.ffs@fw13>

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On Mon, 09 Nov 2026 11:13:41 +0100, Thomas Gleixner wrote:
> 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.
Right, I can reproduce the lost edge here. v2 will use handle_edge_irq()
for edge sources and handle_fasteoi_ack_irq() for level sources.

-- 
Troy Mitchell

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WARNING: multiple messages have this Message-ID (diff)
From: "Troy Mitchell" <troy.mitchell@linux.dev>
To: "Thomas Gleixner" <tglx@kernel.org>
Cc: "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>,
	"Anup Patel" <apatel@ventanamicro.com>,
	<linux-riscv@lists.infradead.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] irqchip/riscv-aplic: Process pending affinity changes on EOI
Date: Tue, 10 Nov 2026 07:15:00 +0000	[thread overview]
Message-ID: <DMRCGHS3V729.FIU61TS3JYWD@linux.dev> (raw)
In-Reply-To: <87pkweuxbe.ffs@fw13>


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On Mon, 09 Nov 2026 11:13:41 +0100, Thomas Gleixner wrote:
> 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.
Right, I can reproduce the lost edge here. v2 will use handle_edge_irq()
for edge sources and handle_fasteoi_ack_irq() for level sources.

-- 
Troy Mitchell

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  reply	other threads:[~2026-11-10  7:15 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
2026-11-09 10:13   ` Thomas Gleixner
2026-11-10  7:15   ` Troy Mitchell [this message]
2026-11-10  7:15     ` Troy Mitchell

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