77 lines
2.3 KiB
Diff
77 lines
2.3 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Sergio Lopez <slp@redhat.com>
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Date: Mon, 16 Sep 2019 13:24:12 +0200
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Subject: [PATCH] virtio-blk: schedule virtio_notify_config to run on main
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context
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virtio_notify_config() needs to acquire the global mutex, which isn't
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allowed from an iothread, and may lead to a deadlock like this:
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- main thead
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* Has acquired: qemu_global_mutex.
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* Is trying the acquire: iothread AioContext lock via
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AIO_WAIT_WHILE (after aio_poll).
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- iothread
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* Has acquired: AioContext lock.
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* Is trying to acquire: qemu_global_mutex (via
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virtio_notify_config->prepare_mmio_access).
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If virtio_blk_resize() is called from an iothread, schedule
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virtio_notify_config() to be run in the main context BH.
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[Removed unnecessary newline as suggested by Kevin Wolf
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<kwolf@redhat.com>.
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--Stefan]
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Signed-off-by: Sergio Lopez <slp@redhat.com>
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Reviewed-by: Kevin Wolf <kwolf@redhat.com>
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Message-id: 20190916112411.21636-1-slp@redhat.com
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Message-Id: <20190916112411.21636-1-slp@redhat.com>
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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---
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hw/block/virtio-blk.c | 16 +++++++++++++++-
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1 file changed, 15 insertions(+), 1 deletion(-)
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diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
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index cbb3729158..0d9adcdaff 100644
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--- a/hw/block/virtio-blk.c
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+++ b/hw/block/virtio-blk.c
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@@ -16,6 +16,7 @@
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#include "qemu/iov.h"
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#include "qemu/module.h"
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#include "qemu/error-report.h"
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+#include "qemu/main-loop.h"
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#include "trace.h"
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#include "hw/block/block.h"
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#include "sysemu/blockdev.h"
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@@ -1082,11 +1083,24 @@ static int virtio_blk_load_device(VirtIODevice *vdev, QEMUFile *f,
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return 0;
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}
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+static void virtio_resize_cb(void *opaque)
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+{
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+ VirtIODevice *vdev = opaque;
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+
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+ assert(qemu_get_current_aio_context() == qemu_get_aio_context());
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+ virtio_notify_config(vdev);
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+}
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+
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static void virtio_blk_resize(void *opaque)
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{
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VirtIODevice *vdev = VIRTIO_DEVICE(opaque);
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- virtio_notify_config(vdev);
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+ /*
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+ * virtio_notify_config() needs to acquire the global mutex,
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+ * so it can't be called from an iothread. Instead, schedule
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+ * it to be run in the main context BH.
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+ */
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+ aio_bh_schedule_oneshot(qemu_get_aio_context(), virtio_resize_cb, vdev);
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}
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static const BlockDevOps virtio_block_ops = {
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--
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2.20.1
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