From: Guenter Roeck <linux@roeck-us.net>
To: David Laight <David.Laight@ACULAB.COM>,
Alan Stern <stern@rowland.harvard.edu>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Gerd Hoffmann <kraxel@redhat.com>
Subject: Re: [PATCH v2] usb: ohci: Prevent missed ohci interrupts
Date: Sat, 27 Apr 2024 15:18:31 -0700 [thread overview]
Message-ID: <d434c88a-6575-4d45-ab3e-e27ac7684b07@roeck-us.net> (raw)
In-Reply-To: <a1b4bac14c6a4334969cc7d671f3a8eb@AcuMS.aculab.com>
On 4/27/24 14:00, David Laight wrote:
> From: Guenter Roeck
>> Sent: 24 April 2024 21:00
>>
>> 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>
>> Fixes: 306c54d0edb6 ("usb: hcd: Try MSI interrupts on PCI devices")
>> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
>> ---
>> v2: Only repeat if the interface is still active
>>
>> drivers/usb/host/ohci-hcd.c | 8 ++++++++
>> 1 file changed, 8 insertions(+)
>>
>> diff --git a/drivers/usb/host/ohci-hcd.c b/drivers/usb/host/ohci-hcd.c
>> index 4f9982ecfb58..bb6b50b4a356 100644
>> --- a/drivers/usb/host/ohci-hcd.c
>> +++ b/drivers/usb/host/ohci-hcd.c
>> @@ -888,6 +888,7 @@ static irqreturn_t ohci_irq (struct usb_hcd *hcd)
>> /* Check for an all 1's result which is a typical consequence
>> * of dead, unclocked, or unplugged (CardBus...) devices
>> */
>> +again:
>> if (ints == ~(u32)0) {
>> ohci->rh_state = OHCI_RH_HALTED;
>> ohci_dbg (ohci, "device removed!\n");
>> @@ -982,6 +983,13 @@ static irqreturn_t ohci_irq (struct usb_hcd *hcd)
>> }
>> spin_unlock(&ohci->lock);
>>
>> + /* repeat until all enabled interrupts are handled */
>> + if (ohci->rh_state != OHCI_RH_HALTED) {
>> + ints = ohci_readl(ohci, ®s->intrstatus);
>> + if (ints & ohci_readl(ohci, ®s->intrenable))
>
> Doesn't the driver know which interrupts are enabled?
> So it should be able to avoid doing two (likely) slow io reads?
> (PCIe reads are pretty much guaranteed to be high latency.)
>
No, the driver does not cache intrenable.
Guenter
next prev parent reply other threads:[~2024-04-27 22:18 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-24 19:59 [PATCH v2] usb: ohci: Prevent missed ohci interrupts Guenter Roeck
2024-04-24 22:30 ` Alan Stern
2024-04-24 22:49 ` Greg Kroah-Hartman
2024-04-24 22:59 ` Guenter Roeck
2024-04-24 22:50 ` Guenter Roeck
2024-04-27 21:00 ` David Laight
2024-04-27 22:18 ` Guenter Roeck [this message]
2024-04-29 6:49 ` Gerd Hoffmann
2024-04-29 13:34 ` Guenter Roeck
2024-04-29 14:01 ` David Laight
2024-04-29 15:23 ` Guenter Roeck
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