Re: [PATCH] hw/vfio-user: wait for proxy close correctly

[Mark Cave-Ayland]

On 10/07/2025 16:47, John Levon wrote:

(added Cedric)
Coverity reported:

CID 1611806: Concurrent data access violations (BAD_CHECK_OF_WAIT_COND)

A wait is performed without a loop. If there is a spurious wakeup, the
condition may not be satisfied.

Fix this by checking ->state for VFIO_PROXY_CLOSED in a loop.

Signed-off-by: John Levon <john.le...@nutanix.com>
---
  hw/vfio-user/proxy.c | 10 ++++++----
  1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/hw/vfio-user/proxy.c b/hw/vfio-user/proxy.c
index c418954440..2275d3fe39 100644
--- a/hw/vfio-user/proxy.c
+++ b/hw/vfio-user/proxy.c
@@ -32,7 +32,6 @@ static void vfio_user_recycle(VFIOUserProxy *proxy, 
VFIOUserMsg *msg);
  
  static void vfio_user_recv(void *opaque);
  static void vfio_user_send(void *opaque);
-static void vfio_user_cb(void *opaque);
  
  static void vfio_user_request(void *opaque);
  
@@ -492,7 +491,7 @@ static void vfio_user_send(void *opaque)
      }
  }
  
-static void vfio_user_cb(void *opaque)
+static void vfio_user_close_cb(void *opaque)
  {
      VFIOUserProxy *proxy = opaque;
  
@@ -984,8 +983,11 @@ void vfio_user_disconnect(VFIOUserProxy *proxy)
       * handler to run after the proxy fd handlers were
       * deleted above.
       */
-    aio_bh_schedule_oneshot(proxy->ctx, vfio_user_cb, proxy);
-    qemu_cond_wait(&proxy->close_cv, &proxy->lock);
+    aio_bh_schedule_oneshot(proxy->ctx, vfio_user_close_cb, proxy);
+
+    while (proxy->state != VFIO_PROXY_CLOSED) {
+        qemu_cond_wait(&proxy->close_cv, &proxy->lock);
+    }
  
      /* we now hold the only ref to proxy */
      qemu_mutex_unlock(&proxy->lock);

It think it is worth mentioning the function rename in the commit 
message, otherwise looks good to me:

Reviewed-by: Mark Cave-Ayland <markcaveayl...@nutanix.com>


ATB,

Mark.