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Blame SOURCES/kvm-usb-host-skip-open-on-pending-postload-bh.patch

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From 020cf375b572ccbda55ad45e34b7cb7ad2a469a2 Mon Sep 17 00:00:00 2001
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From: Gerd Hoffmann <kraxel@redhat.com>
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Date: Wed, 13 Jun 2018 14:07:30 +0200
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Subject: [PATCH 151/268] usb-host: skip open on pending postload bh
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RH-Author: Gerd Hoffmann <kraxel@redhat.com>
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Message-id: <20180613140730.16401-2-kraxel@redhat.com>
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Patchwork-id: 80667
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O-Subject: [RHEL-7.6 qemu-kvm-rhev PATCH 1/1] usb-host: skip open on pending postload bh
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Bugzilla: 1572851
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RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
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RH-Acked-by: Laurent Vivier <lvivier@redhat.com>
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usb-host emulates a device unplug after live migration, because the
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device state is unknown and unplug/replug makes sure the guest
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re-initializes the device into a working state.  This can't be done in
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post-load though, so post-load just schedules a bottom half which
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executes after vmload is complete.
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It can happen that the device autoscan timer hits the race window
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between scheduling and running the bottom half, which in turn can
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triggers an assert().
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Fix that issue by just ignoring the usb_host_open() call in case the
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bottom half didn't execute yet.
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Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1572851
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Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
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Message-id: 20180503062932.17233-1-kraxel@redhat.com
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(cherry picked from commit 3280ea8edede3814553aa19fa27a58daedd48ad9)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 hw/usb/host-libusb.c | 7 +++++++
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 1 file changed, 7 insertions(+)
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diff --git a/hw/usb/host-libusb.c b/hw/usb/host-libusb.c
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index 1b0be07..0290fb8 100644
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--- a/hw/usb/host-libusb.c
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+++ b/hw/usb/host-libusb.c
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@@ -102,6 +102,7 @@ struct USBHostDevice {
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     /* callbacks & friends */
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     QEMUBH                           *bh_nodev;
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     QEMUBH                           *bh_postld;
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+    bool                             bh_postld_pending;
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     Notifier                         exit;
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     /* request queues */
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@@ -866,6 +867,10 @@ static int usb_host_open(USBHostDevice *s, libusb_device *dev)
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     int rc;
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     Error *local_err = NULL;
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+    if (s->bh_postld_pending) {
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+        return -1;
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+    }
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+
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     trace_usb_host_open_started(bus_num, addr);
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     if (s->dh != NULL) {
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@@ -1524,6 +1529,7 @@ static void usb_host_post_load_bh(void *opaque)
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     if (udev->attached) {
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         usb_device_detach(udev);
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     }
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+    dev->bh_postld_pending = false;
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     usb_host_auto_check(NULL);
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 }
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@@ -1535,6 +1541,7 @@ static int usb_host_post_load(void *opaque, int version_id)
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         dev->bh_postld = qemu_bh_new(usb_host_post_load_bh, dev);
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     }
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     qemu_bh_schedule(dev->bh_postld);
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+    dev->bh_postld_pending = true;
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     return 0;
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 }
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-- 
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1.8.3.1
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