linux-kernel - Re: MSI interrupts and disable

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Message-ID: <86802c440710132259o6e82f6s4bed7b25bd5636e9@mail.gmail.com>
Date:	Sat, 13 Oct 2007 22:59:15 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Manfred Spraul" <manfred@...orfullife.com>
Cc:	"Jeff Garzik" <jgarzik@...ox.com>,
	"Ayaz Abdulla" <aabdulla@...dia.com>,
	nedev <netdev@...r.kernel.org>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	"David Miller" <davem@...emloft.net>,
	"Andrew Morton" <akpm@...ux-foundation.org>
Subject: Re: MSI interrupts and disable_irq

On 10/13/07, Manfred Spraul <manfred@...orfullife.com> wrote:
> Jeff Garzik wrote:
> >
> > I think the scenario you outline is an illustration of the approach's
> > fragility:  disable_irq() is a heavy hammer that originated with INTx,
> > and it relies on a chip-specific disable method (kernel/irq/manage.c)
> > that practically guarantees behavior will vary across MSI/INTx/etc.
> >
> I checked the code: IRQ_DISABLE is implemented in software, i.e.
> handle_level_irq() only calls handle_IRQ_event() [and then the nic irq
> handler] if IRQ_DISABLE is not set.
> OTHO: The last trace looks as if nv_do_nic_poll() is interrupted by an irq.
>
> Perhaps something corrupts dev->irq? The irq is requested with
>     request_irq(np->pci_dev->irq, handler, IRQF_SHARED, dev->name, dev)
> and disabled with
>     disable_irq_lockdep(dev->irq);
>
> Someone around with a MSI capable board? The forcedeth driver does
>     dev->irq = pci_dev->irq
> in nv_probe(), especially before pci_enable_msi().
> Does pci_enable_msi() change pci_dev->irq? Then we would disable the
> wrong interrupt....

the request_irq==>setup_irq will make dev->irq = pci_dev->irq.

YH
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