[Qemu-devel] [PULL 2/2] ehci: stop recursive calls to ehci_work_bh

[Gerd Hoffmann <kraxel@redhat.com>]

Can happen with usb-storage devices: ehci_work_bh calls usb-storage,
usb-storage calls into block layer, block layer may run BHs.

Add a simple bool and just do nothing in case we figure ehci_work_bh is
active.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 20170612073109.25930-1-kraxel@redhat.com
---
 hw/usb/hcd-ehci.h | 1 +
 hw/usb/hcd-ehci.c | 7 +++++++
 2 files changed, 8 insertions(+)

diff --git a/hw/usb/hcd-ehci.h b/hw/usb/hcd-ehci.h
index 938d8aa284..821f1ded43 100644
--- a/hw/usb/hcd-ehci.h
+++ b/hw/usb/hcd-ehci.h
@@ -297,6 +297,7 @@ struct EHCIState {
      */
     QEMUTimer *frame_timer;
     QEMUBH *async_bh;
+    bool working;
     uint32_t astate;         /* Current state in asynchronous schedule */
     uint32_t pstate;         /* Current state in periodic schedule     */
     USBPort ports[NB_PORTS];
diff --git a/hw/usb/hcd-ehci.c b/hw/usb/hcd-ehci.c
index 17c572c55f..73090e01ad 100644
--- a/hw/usb/hcd-ehci.c
+++ b/hw/usb/hcd-ehci.c
@@ -2241,6 +2241,11 @@ static void ehci_work_bh(void *opaque)
     uint64_t uframes, skipped_uframes;
     int i;
 
+    if (ehci->working) {
+        return;
+    }
+    ehci->working = true;
+
     t_now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
     ns_elapsed = t_now - ehci->last_run_ns;
     uframes = ns_elapsed / UFRAME_TIMER_NS;
@@ -2322,6 +2327,8 @@ static void ehci_work_bh(void *opaque)
         }
         timer_mod(ehci->frame_timer, expire_time);
     }
+
+    ehci->working = false;
 }
 
 static void ehci_work_timer(void *opaque)
-- 
2.9.3