linux-kernel - Re: [PATCH] PCI/LINK: Request a one-shot IRQ with NULL handler

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Date:   Mon, 25 Mar 2019 13:27:15 -0500
From:   "Alex G." <mr.nuke.me@...il.com>
To:     Borislav Petkov <bp@...en8.de>, LKML <linux-kernel@...r.kernel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lukas Wunner <lukas@...ner.de>, linux-pci@...r.kernel.org
Subject: Re: [PATCH] PCI/LINK: Request a one-shot IRQ with NULL handler

Hi Borislav,

Thanks for the update. We've settled on a different fix [1], since Lukas 
was not happy with IRQF_ONESHOT [2].

Alex

[1] 
https://lore.kernel.org/linux-pci/20190323003700.7294-1-mr.nuke.me@gmail.com/
[2] 
https://lore.kernel.org/linux-pci/20190318043314.noyj6t4sh26spuzt@wunner.de/

On 3/25/19 1:23 PM, Borislav Petkov wrote:
> From: Borislav Petkov <bp@...e.de>
> 
> Booting v5.1-rc1 causes these new messages in dmesg here:
> 
>    genirq: Threaded irq requested with handler=NULL and !ONESHOT for irq 24
>    pcie_bw_notification: probe of 0000:00:02.0:pcie010 failed with error -22
> 
> because requesting a threaded IRQ with NULL handler needs to be oneshot.
> Otherwise a level-triggered interrupt endless loop can happen, see the
> detailed explanation above the "Threaded irq... " error message in
> kernel/irq/manage.c.
> 
> And PCI-MSI type interrupts are one-shot safe but not in the IOAPIC
> case:
> 
>    24: ... IO-APIC   28-fasteoi   PCIe BW notif, PCIe BW notif, PCIe BW notif
>    25: ... IO-APIC   29-fasteoi   PCIe BW notif, PCIe BW notif
> 
> Make the BW notification handler oneshot too.
> 
> Fixes: e8303bb7a75c ("PCI/LINK: Report degraded links via link bandwidth notification")
> Suggested-by: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Borislav Petkov <bp@...e.de>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: Lukas Wunner <lukas@...ner.de>
> Cc: Alexandru Gagniuc <mr.nuke.me@...il.com>
> Cc: linux-pci@...r.kernel.org
> ---
>   drivers/pci/pcie/bw_notification.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/pcie/bw_notification.c b/drivers/pci/pcie/bw_notification.c
> index d2eae3b7cc0f..16e11c09f6bd 100644
> --- a/drivers/pci/pcie/bw_notification.c
> +++ b/drivers/pci/pcie/bw_notification.c
> @@ -81,7 +81,7 @@ static int pcie_bandwidth_notification_probe(struct pcie_device *srv)
>   		return -ENODEV;
>   
>   	ret = request_threaded_irq(srv->irq, NULL, pcie_bw_notification_handler,
> -				   IRQF_SHARED, "PCIe BW notif", srv);
> +				   IRQF_SHARED | IRQF_ONESHOT, "PCIe BW notif", srv);
>   	if (ret)
>   		return ret;
>   
>