From patchwork Wed Jan 6 19:45:24 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Laurent Vivier X-Patchwork-Id: 564065 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id ADB311402E2 for ; Thu, 7 Jan 2016 06:46:48 +1100 (AEDT) Received: from localhost ([::1]:55891 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aGu2g-0006c1-JH for incoming@patchwork.ozlabs.org; Wed, 06 Jan 2016 14:46:46 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42771) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aGu1T-0004dK-RK for qemu-devel@nongnu.org; Wed, 06 Jan 2016 14:45:33 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aGu1R-00082b-Mk for qemu-devel@nongnu.org; Wed, 06 Jan 2016 14:45:31 -0500 Received: from mx1.redhat.com ([209.132.183.28]:41713) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aGu1R-00082X-Gq for qemu-devel@nongnu.org; Wed, 06 Jan 2016 14:45:29 -0500 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (Postfix) with ESMTPS id 22C5636B1BB for ; Wed, 6 Jan 2016 19:45:29 +0000 (UTC) Received: from thinkpad.redhat.com (vpn1-4-184.ams2.redhat.com [10.36.4.184]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u06JjPn4003490; Wed, 6 Jan 2016 14:45:27 -0500 From: Laurent Vivier To: qemu-devel@nongnu.org Date: Wed, 6 Jan 2016 20:45:24 +0100 Message-Id: <1452109525-32150-2-git-send-email-lvivier@redhat.com> In-Reply-To: <1452109525-32150-1-git-send-email-lvivier@redhat.com> References: <1452109525-32150-1-git-send-email-lvivier@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.23 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: lvivier@redhat.com, thuth@redhat.com, kraxel@redhat.com Subject: [Qemu-devel] [PATCH v2 1/2] ohci: delay first SOF interrupt X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org 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. This does not happen on real hardware because real hardware never send interrupt immediately after the controller has been moved to OPERATION state. This patch tries to delay the first SOF interrupt to let driver exits from the critical section (which is not protected against interrupts...) 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_resume(): the driver re-enables operation with OHCI_USB_OPER. In QEMU this start the SOF timer and QEMU starts to send IRQs. As the driver is not in OHCI_STATE_RUNNING and not protected against IRQ, the ohci_irq() can be called and the driver never moved to OHCI_STATE_RUNNING. Suggested-by: Gerd Hoffmann Signed-off-by: Laurent Vivier Reviewed-by: Thomas Huth --- hw/usb/hcd-ohci.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/hw/usb/hcd-ohci.c b/hw/usb/hcd-ohci.c index 7d65818..a44fab2 100644 --- a/hw/usb/hcd-ohci.c +++ b/hw/usb/hcd-ohci.c @@ -1231,11 +1231,16 @@ static int ohci_service_ed_list(OHCIState *ohci, uint32_t head, int completion) return active; } -/* Generate a SOF event, and set a timer for EOF */ -static void ohci_sof(OHCIState *ohci) +/* set a timer for EOF */ +static void ohci_eof_timer(OHCIState *ohci) { ohci->sof_time = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); timer_mod(ohci->eof_timer, ohci->sof_time + usb_frame_time); +} +/* Set a timer for EOF and generate a SOF event */ +static void ohci_sof(OHCIState *ohci) +{ + ohci_eof_timer(ohci); ohci_set_interrupt(ohci, OHCI_INTR_SF); } @@ -1343,7 +1348,12 @@ static int ohci_bus_start(OHCIState *ohci) trace_usb_ohci_start(ohci->name); - ohci_sof(ohci); + /* Delay the first SOF event by one frame time as + * linux driver is not ready to receive it and + * can meet some race conditions + */ + + ohci_eof_timer(ohci); return 1; }