From: "Maciej W. Rozycki" <macro@orcam.me.uk>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: netdev@vger.kernel.org, linux-mips@vger.kernel.org,
Jakub Kicinski <kuba@kernel.org>,
Andrew Lunn <andrew+netdev@lunn.ch>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Paolo Abeni <pabeni@redhat.com>
Subject: Re: [PATCH net-next v2] declance: Remove IRQF_ONESHOT
Date: Tue, 5 May 2026 15:00:56 +0100 (BST) [thread overview]
Message-ID: <alpine.DEB.2.21.2605051410280.46195@angie.orcam.me.uk> (raw)
In-Reply-To: <20260505123203.jifiaxEL@linutronix.de>
On Tue, 5 May 2026, Sebastian Andrzej Siewior wrote:
> > > With force-threading enabled, the interrupt handler is masked in the
> > > IRQ-chip until after the threaded-handler run. See the cond_unmask_irq()
> > > in handle_level_irq() or the mask_irq() & cond_unmask_eoi_irq() in
> > > handle_fasteoi_ack_irq(). That means the hw-IRQ is done, the thread is
> > > running with interrupts enabled but the hw-IRQ will not trigger again.
> > > The cited commit 5a4a4ad851dd8 ("MIPS: Mark cascade and low level
> > > interrupts IRQF_NO_THREAD") is different as it acts on cascading
> > > interrupts which is not what we have here.
> >
> > Not with the current handle_fasteoi_irq() handler.
>
> Why? There is a mask_irq() in the ONESHOT case.
Yes, in that case there is.
> > > If you request a threaded interrupt you must either provide two handler
> > > and the primary must mask the interrupt so it does not fire again or you
> > > pass a flag such as IRQF_ONESHOT and which point the IRQ subsystem will
> > > mask the IRQ within the irqchip so it does not fire again.
> >
> > Well, yes, but you've just removed the flag from this driver, so either
> > the flag has to reinstated or the driver adjusted differently for the
> > threaded case to be handled correctly.
>
> But there is a plain request_irq() so the handler is invoked directly in
> hardirq context with disabled interrupts. In forced-threaded context,
> such as on PREEMPT_RT, the IRQF_ONESHOT is added.
Ah, I missed that IRQF_ONESHOT bit in irq_setup_forced_threading(). So
it seems like we're good. I'll proceed with the original change then to
just amend IOASIC DMA IRQ documentation. Thank you for patience again.
Maciej
next prev parent reply other threads:[~2026-05-05 14:00 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-27 13:53 [PATCH net-next v2] declance: Remove IRQF_ONESHOT Sebastian Andrzej Siewior
2026-01-27 15:46 ` Maciej W. Rozycki
2026-01-27 16:54 ` Sebastian Andrzej Siewior
2026-01-27 18:35 ` Maciej W. Rozycki
2026-03-29 20:27 ` Maciej W. Rozycki
2026-05-04 22:35 ` Maciej W. Rozycki
2026-05-05 7:29 ` Sebastian Andrzej Siewior
2026-05-05 12:02 ` Maciej W. Rozycki
2026-05-05 12:32 ` Sebastian Andrzej Siewior
2026-05-05 14:00 ` Maciej W. Rozycki [this message]
2026-05-05 15:24 ` Sebastian Andrzej Siewior
2026-05-06 9:25 ` Maciej W. Rozycki
2026-05-07 7:34 ` Sebastian Andrzej Siewior
2026-05-07 11:45 ` Maciej W. Rozycki
2026-01-29 3:50 ` patchwork-bot+netdevbpf
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