From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50814) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1a9CIo-0005ou-Ah for qemu-devel@nongnu.org; Wed, 16 Dec 2015 08:39:35 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1a9CIk-0000vv-A8 for qemu-devel@nongnu.org; Wed, 16 Dec 2015 08:39:34 -0500 Received: from mx1.redhat.com ([209.132.183.28]:44163) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1a9CIk-0000vr-5L for qemu-devel@nongnu.org; Wed, 16 Dec 2015 08:39:30 -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 C9DBAC0B7E0D for ; Wed, 16 Dec 2015 13:39:29 +0000 (UTC) From: Laurent Vivier Date: Wed, 16 Dec 2015 14:39:25 +0100 Message-Id: <1450273165-2367-3-git-send-email-lvivier@redhat.com> In-Reply-To: <1450273165-2367-1-git-send-email-lvivier@redhat.com> References: <1450273165-2367-1-git-send-email-lvivier@redhat.com> Subject: [Qemu-devel] [PATCH 2/2] ohci: clear pending SOF on suspend List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: lvivier@redhat.com, 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 --- 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 5f15ebb..b5a4e39 100644 --- a/hw/usb/hcd-ohci.c +++ b/hw/usb/hcd-ohci.c @@ -1438,6 +1438,9 @@ static void ohci_set_ctl(OHCIState *ohci, uint32_t val) break; case OHCI_USB_SUSPEND: ohci_bus_stop(ohci); + /* clear pending SF otherwise 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