From cc6f14a54a4d4cdd6da634366b613da600105729 Mon Sep 17 00:00:00 2001 From: Laurent Vivier Date: Mon, 11 Jan 2016 08:48:58 +0100 Subject: [PATCH 2/3] ohci: clear pending SOF on suspend Message-id: <1452502138-10185-3-git-send-email-lvivier@redhat.com> Patchwork-id: 68728 O-Subject: [RHEL-7.2.z qemu-kvm-rhev PATCH v2 2/2] ohci: clear pending SOF on suspend Bugzilla: 1298971 RH-Acked-by: David Gibson RH-Acked-by: Thomas Huth RH-Acked-by: Gerd Hoffmann 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 Reviewed-by: Thomas Huth Message-id: 1452109525-32150-3-git-send-email-lvivier@redhat.com Signed-off-by: Gerd Hoffmann (cherry picked from commit 087462c7739869e9b888c06c06c8f1bbfd99779c) Signed-off-by: Laurent Vivier BZ: https://bugzilla.redhat.com/show_bug.cgi?id=1275555 --- hw/usb/hcd-ohci.c | 3 +++ 1 file changed, 3 insertions(+) Signed-off-by: Miroslav Rezanina --- 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); -- 1.8.3.1