linux-kernel - Re: [POSSIBLE BUG] behavior change in irq_can_handle

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Message-ID: <CAMOZA0Luhva=s3O8qawEf7YiKbUQRBeK0t4FX-SBTcPgRGOSfg@mail.gmail.com>
Date: Thu, 13 Nov 2025 10:02:33 +0100
From: Luigi Rizzo <lrizzo@...gle.com>
To: linux-kernel@...r.kernel.org, maz@...nel.org, tglx@...utronix.de
Cc: Luigi Rizzo <rizzo.unipi@...il.com>, Sean Christopherson <seanjc@...gle.com>, 
	Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [POSSIBLE BUG] behavior change in irq_can_handle_pm() introduced
 in 8d39d6ec4db5d

On Sat, Nov 8, 2025 at 10:30 PM Luigi Rizzo <lrizzo@...gle.com> wrote:
>
> BACKGROUND (just to explain how I found the issue; it may exist regardless):
>
> I have some code (soon to be posted here) to implement interrupt moderation
> in software using using per-CPU hrtimers. The basic logic is the following:
>
> - if the system decides an irq needs moderation, it calls disable_irq_nosync(),
>   adds the irq_desc in a per-cpu list, and keeps IRQD_IRQ_INPROGRESS set
>   to prevent migration. The first desc inserted in the list also start

never mind this thread. I found that disable_irq_nosync()
is enough to make  irq_can_handle() return false
(through irq_can_handle_actions()) and that prevents
handle_edge_irq() from calling the handler.
In the end, that simplifies my use case!

Sorry for the noise.

cheers
luigi