On Tue, Dec 07, 2021 at 15:08:02 +0000, Daniel P. Berrangé wrote:

On Tue, Dec 07, 2021 at 04:02:11PM +0100, Peter Krempa wrote:

On Tue, Dec 07, 2021 at 14:53:20 +0000, Daniel P. Berrangé wrote:

On Tue, Dec 07, 2021 at 05:34:00AM -0800, Rohit Kumar wrote:

This patch is to determine the VM which had IO or socket hangup error.

Signed-off-by: Rohit Kumar <rohit.kumar3@nutanix.com>
---
 src/qemu/qemu_monitor.c | 46 +++++++++++++++++++++++++----------------
 1 file changed, 28 insertions(+), 18 deletions(-)

diff --git a/src/qemu/qemu_monitor.c b/src/qemu/qemu_monitor.c
index 75e0e4ed92..d36db280d9 100644
--- a/src/qemu/qemu_monitor.c
+++ b/src/qemu/qemu_monitor.c
@@ -530,13 +530,19 @@ qemuMonitorIO(GSocket *socket G_GNUC_UNUSED,
     qemuMonitor *mon = opaque;
     bool error = false;
     bool hangup = false;
+    virDomainObj *vm = mon->vm;
+    g_autofree char *vmName = NULL;
+
+    if (vm != NULL && vm->def != NULL) {
+        vmName = g_strdup(vm->def->name);
+    }

This looks a little questionable.

Although we hold a reference on 'vm', this code doesn't do anything
to protect its access of 'vm->def'. If we were protected when accesing
vm->def, then we wouldn't need to strdup it anyway.

Additionally we also regularly log the monitor pointer and VM name when
entering the monitor context:

See qemuDomainObjEnterMonitorInternal:

VIR_DEBUG("Entering monitor (mon=%p vm=%p name=%s)",
          priv->mon, obj, obj->def->name);

In that place we are correctly still in the 'vm' context so we can
reference the name.

This call is usually very close to any other monitor calls or can be
easily looked up, so I don't think it's worth to increase the complexity
of the monitor code just to put the VM name in every single debug
message.

I'd be in favour of /consistently/ having  'mon=%p vm=%p' for all
monitor debug logs though.

Use %p for 'vm' is fine as it doesn't break the locking boundary, but
the patch is doing %s for vm->def->name, which, if done properly would
make the code way more complex with questionable benefits.