ehci: fix frame timer invocation.

ehci registers ehci_frame_timer as both timer and bottom half, which
turned out to be a bad idea as it can be called as bottom half then
while it is running as timer, and it isn't prepared to handle recursive
calls.

Change the timer func to just schedule the bottom half to avoid this.

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1449609
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 20170519120428.25981-1-kraxel@redhat.com

hw/usb/hcd-ehci.c

@@ -2232,7 +2232,7 @@ static void ehci_update_frindex(EHCIState *ehci, int uframes)
     ehci->frindex = (ehci->frindex + uframes) % 0x4000;
 }
 
-static void ehci_frame_timer(void *opaque)
+static void ehci_work_bh(void *opaque)
 {
     EHCIState *ehci = opaque;
     int need_timer = 0;
@@ -2324,6 +2324,13 @@ static void ehci_frame_timer(void *opaque)
     }
 }
 
+static void ehci_work_timer(void *opaque)
+{
+    EHCIState *ehci = opaque;
+
+    qemu_bh_schedule(ehci->async_bh);
+}
+
 static const MemoryRegionOps ehci_mmio_caps_ops = {
     .read = ehci_caps_read,
     .write = ehci_caps_write,
@@ -2478,8 +2485,8 @@ void usb_ehci_realize(EHCIState *s, DeviceState *dev, Error **errp)
         s->ports[i].dev = 0;
     }
 
-    s->frame_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, ehci_frame_timer, s);
-    s->async_bh = qemu_bh_new(ehci_frame_timer, s);
+    s->frame_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, ehci_work_timer, s);
+    s->async_bh = qemu_bh_new(ehci_work_bh, s);
     s->device = dev;
 
     s->vmstate = qemu_add_vm_change_state_handler(usb_ehci_vm_state_change, s);