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Date: Tue, 30 Apr 2024 10:10:35 +0200
From: Gerd Hoffmann <kraxel@redhat.com>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Alan Stern <stern@rowland.harvard.edu>, 
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, 
	David Laight <David.Laight@aculab.com>
Subject: Re: [PATCH v3] usb: ohci: Prevent missed ohci interrupts
Message-ID: <723ahlmaul2l2mpqfdykufwz5lyyvhhehbpx5ya6eopquq6mro@qo6h2wnbqm36>
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On Mon, Apr 29, 2024 at 08:40:10AM GMT, Guenter Roeck wrote:
> Testing ohci functionality with qemu's pci-ohci emulation often results
> in ohci interface stalls, resulting in hung task timeouts.
> 
> The problem is caused by lost interrupts between the emulation and the
> Linux kernel code. Additional interrupts raised while the ohci interrupt
> handler in Linux is running and before the handler clears the interrupt
> status are not handled. The fix for a similar problem in ehci suggests
> that the problem is likely caused by edge-triggered MSI interrupts. See
> commit 0b60557230ad ("usb: ehci: Prevent missed ehci interrupts with
> edge-triggered MSI") for details.
> 
> Ensure that the ohci interrupt code handles all pending interrupts before
> returning to solve the problem.
> 
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> Cc: David Laight <David.Laight@aculab.com>
> Cc: stable@vger.kernel.org
> Fixes: 306c54d0edb6 ("usb: hcd: Try MSI interrupts on PCI devices")
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
> v3: Check if any interrupts are pending before reading intrenable
>     Add 'Cc: stable@vger.kernel.org'
> v2: Only repeat if the interface is still active

Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>

take care,
  Gerd