From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34788) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aHRpI-0001p7-UQ for qemu-devel@nongnu.org; Fri, 08 Jan 2016 02:51:13 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aHRpF-0007Kh-Nd for qemu-devel@nongnu.org; Fri, 08 Jan 2016 02:51:12 -0500 Received: from mx1.redhat.com ([209.132.183.28]:52055) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aHRpF-0007Kd-IR for qemu-devel@nongnu.org; Fri, 08 Jan 2016 02:51:09 -0500 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (Postfix) with ESMTPS id 2BC1C33E5EB for ; Fri, 8 Jan 2016 07:51:09 +0000 (UTC) References: <1452109525-32150-1-git-send-email-lvivier@redhat.com> <1452109525-32150-3-git-send-email-lvivier@redhat.com> From: Thomas Huth Message-ID: <568F6A6A.4010206@redhat.com> Date: Fri, 8 Jan 2016 08:51:06 +0100 MIME-Version: 1.0 In-Reply-To: <1452109525-32150-3-git-send-email-lvivier@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2 2/2] ohci: clear pending SOF on suspend List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Laurent Vivier , qemu-devel@nongnu.org Cc: kraxel@redhat.com On 06.01.2016 20:45, Laurent Vivier wrote: > On overcommitted CPU, kernel can be so slow that an interrupt can > be triggered by the device whereas the driver is not ready to receive > it. This drives us into an infinite loop. > > On suspend, if a SOF interrupt is raised between the stop of the > device processing and the change of the device internal state to > OHCI_USB_SUSPEND (QEMU stops SOF timer on this state change), this > interrupt is never acknowledged. > > This patch clears pending SOF interrupt on OHCI_USB_SUSPEND setting. > > Some details: > > - ohci_irq(): the OHCI interrupt handler, acknowledges the SOF IRQ > only if the state of the driver (rh_state) is OHCI_STATE_RUNNING. > So if this interrupt happens and the driver is not in this state, > the function is called again and again, moving the system to a > CPU starvation. > > - ohci_rh_suspend(): the function stop the operation and acknowledge > pending interrupts (but doesn't disable it). Later in the function, > the device is moved to OHCI_SUSPEND_STATE, and the driver to > OHCI_RH_SUSPENDED. If between the moment when the interrupt is > acknowledged and the moment when the device is suspended a new > interrupt is raised, it will be never acknowledged because the > driver is now not in OHCI_RH_RUNNING state. > > Signed-off-by: Laurent Vivier > --- > hw/usb/hcd-ohci.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/hw/usb/hcd-ohci.c b/hw/usb/hcd-ohci.c > index a44fab2..b99e44f 100644 > --- a/hw/usb/hcd-ohci.c > +++ b/hw/usb/hcd-ohci.c > @@ -1446,6 +1446,9 @@ static void ohci_set_ctl(OHCIState *ohci, uint32_t val) > break; > case OHCI_USB_SUSPEND: > ohci_bus_stop(ohci); > + /* clear pending SF otherwise linux driver loops in ohci_irq() */ > + ohci->intr_status &= ~OHCI_INTR_SF; > + ohci_intr_update(ohci); > break; > case OHCI_USB_RESUME: > trace_usb_ohci_resume(ohci->name); > Reviewed-by: Thomas Huth