[PATCH] Fix race condition when detaching a device

[Pierre Libeau]

Hello guys,


I will very happy if you have time to give me feedback about this patch.

It's the first time for me about libvirt project so don't hesitate to say me if I have missed something.


I have pushed this change on my side internally and it's resolved my issue.


Pierre
________________________________
De : Pierre Libeau
Envoyé : mercredi 31 août 2022 14:22:51
À : libvir-list at redhat.com
Cc : Pierre Libeau
Objet : [PATCH] Fix race condition when detaching a device

Qemu reply to libvirt "DeviceNotFound" and libvirt didn't clean on the
side the live configuration.

qemuMonitorDelDevice() return -2 to qemuDomainDeleteDevice() and during
this action in qemuDomainDetachDeviceLive() the remove is never call.

Ref #359

Signed-off-by: Pierre LIBEAU <pierre.libeau at corp.ovh.com>
---
 src/qemu/qemu_hotplug.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
index 9b508dc8f0..52a14a4476 100644
--- a/src/qemu/qemu_hotplug.c
+++ b/src/qemu/qemu_hotplug.c
@@ -93,6 +93,8 @@ qemuDomainResetDeviceRemoval(virDomainObj *vm);
  *
  * Returns: 0 on success,
  *         -1 otherwise.
+ *         -2 device does not exist in qemu, but it still
+ *            exists in libvirt
  */
 static int
 qemuDomainDeleteDevice(virDomainObj *vm,
@@ -124,7 +126,6 @@ qemuDomainDeleteDevice(virDomainObj *vm,
              * domain XML is queried right after detach API the
              * device would still be there.  */
             VIR_DEBUG("Detaching of device %s failed and no event arrived", alias);
-            rc = 0;
         }
     }

@@ -6055,7 +6056,11 @@ qemuDomainDetachDeviceLive(virDomainObj *vm,
     if (!async)
         qemuDomainMarkDeviceForRemoval(vm, info);

-    if (qemuDomainDeleteDevice(vm, info->alias) < 0) {
+    int rc;
+    rc = qemuDomainDeleteDevice(vm, info->alias);
+    if (rc < 0) {
+        if (rc == -2)
+               ret = qemuDomainRemoveDevice(driver, vm, &detach);
         if (virDomainObjIsActive(vm))
             qemuDomainRemoveAuditDevice(vm, &detach, false);
         goto cleanup;
--
2.37.3

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