Re: [Qemu-devel] [PATCH 4/4] spice: drop obsolete iothread locking

[Bing Bu Cao]

Hi,Gerd

I found the lock has been revert in qemu-kvm repository and
qemu-kvm on RHEL6.3 with spice/qxl has one problem:


Doing some display configuration (such as changing resolution) in guest will involve in deadlock in guest,meanwhile
which affect the host hang for a long while.


I wonder whether this patch should be revert back in qemu-kvm again?
Actually, I have no idea why added in QEMU but not in qemu-kvm? :)


On 04/29/2011 05:38 PM, Gerd Hoffmann wrote:

We don't use qemu internals from spice server context any more.
Thus we don't also need to grab the iothread mutex from spice
server context.  And we don't have to temporarely release the
lock to avoid deadlocks.  Drop all the calls.

Signed-off-by: Gerd Hoffmann <address@hidden>
---
 hw/qxl.c           |    8 --------
 ui/spice-display.c |    6 ------
 2 files changed, 0 insertions(+), 14 deletions(-)

diff --git a/hw/qxl.c b/hw/qxl.c
index 4dfddf0..2bb36c6 100644
--- a/hw/qxl.c
+++ b/hw/qxl.c
@@ -666,10 +666,8 @@ static void qxl_hard_reset(PCIQXLDevice *d, int loadvm)
     dprint(d, 1, "%s: start%s\n", __FUNCTION__,
            loadvm ? " (loadvm)" : "");
 
-    qemu_mutex_unlock_iothread();
     d->ssd.worker->reset_cursor(d->ssd.worker);
     d->ssd.worker->reset_image_cache(d->ssd.worker);
-    qemu_mutex_lock_iothread();
     qxl_reset_surfaces(d);
     qxl_reset_memslots(d);
 
@@ -799,9 +797,7 @@ static void qxl_reset_surfaces(PCIQXLDevice *d)
 {
     dprint(d, 1, "%s:\n", __FUNCTION__);
     d->mode = QXL_MODE_UNDEFINED;
-    qemu_mutex_unlock_iothread();
     d->ssd.worker->destroy_surfaces(d->ssd.worker);
-    qemu_mutex_lock_iothread();
     memset(&d->guest_surfaces.cmds, 0, sizeof(d->guest_surfaces.cmds));
 }
 
@@ -870,9 +866,7 @@ static void qxl_destroy_primary(PCIQXLDevice *d)
     dprint(d, 1, "%s\n", __FUNCTION__);
 
     d->mode = QXL_MODE_UNDEFINED;
-    qemu_mutex_unlock_iothread();
     d->ssd.worker->destroy_primary_surface(d->ssd.worker, 0);
-    qemu_mutex_lock_iothread();
 }
 
 static void qxl_set_mode(PCIQXLDevice *d, int modenr, int loadvm)
@@ -942,10 +936,8 @@ static void ioport_write(void *opaque, uint32_t addr, uint32_t val)
     case QXL_IO_UPDATE_AREA:
     {
         QXLRect update = d->ram->update_area;
-        qemu_mutex_unlock_iothread();
         d->ssd.worker->update_area(d->ssd.worker, d->ram->update_surface,
                                    &update, NULL, 0, 0);
-        qemu_mutex_lock_iothread();
         break;
     }
     case QXL_IO_NOTIFY_CMD:
diff --git a/ui/spice-display.c b/ui/spice-display.c
index 1e1a35d..34201cd 100644
--- a/ui/spice-display.c
+++ b/ui/spice-display.c
@@ -176,18 +176,14 @@ void qemu_spice_create_host_primary(SimpleSpiceDisplay *ssd)
     surface.mem        = (intptr_t)ssd->buf;
     surface.group_id   = MEMSLOT_GROUP_HOST;
 
-    qemu_mutex_unlock_iothread();
     ssd->worker->create_primary_surface(ssd->worker, 0, &surface);
-    qemu_mutex_lock_iothread();
 }
 
 void qemu_spice_destroy_host_primary(SimpleSpiceDisplay *ssd)
 {
     dprint(1, "%s:\n", __FUNCTION__);
 
-    qemu_mutex_unlock_iothread();
     ssd->worker->destroy_primary_surface(ssd->worker, 0);
-    qemu_mutex_lock_iothread();
 }
 
 void qemu_spice_vm_change_state_handler(void *opaque, int running, int reason)
@@ -197,9 +193,7 @@ void qemu_spice_vm_change_state_handler(void *opaque, int running, int reason)
     if (running) {
         ssd->worker->start(ssd->worker);
     } else {
-        qemu_mutex_unlock_iothread();
         ssd->worker->stop(ssd->worker);
-        qemu_mutex_lock_iothread();
     }
     ssd->running = running;
 }