[libvirt] [PATCH] qemu: lock: unlock vm during qemuBuildCommandLine

[Peter Krempa]

On Thu, Apr 23, 2015 at 11:44:49 +0800, zhang bo wrote:
> The function qemuBuildCommandLine() may take a long time, for example
> if we configure tens of vifs for the guest, each may cost hundrands of
> milliseconds to create tap dev, senconds in total. Thus, unlock vm
> before calling it.
> 
> Signed-off-by: Zhang Bo <oscar.zhangbo at huawei.com>
> Signed-off-by: Zhou Yimin <zhouyimin at huawei.com>
> ---
>  src/qemu/qemu_process.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
> index 753afe8..d1aaaec 100644
> --- a/src/qemu/qemu_process.c
> +++ b/src/qemu/qemu_process.c
> @@ -4628,14 +4628,18 @@ int qemuProcessStart(virConnectPtr conn,
>      }
> 
>      VIR_DEBUG("Building emulator command line");
> +    virObjectUnlock(vm);
>      if (!(cmd = qemuBuildCommandLine(conn, driver, vm->def, priv->monConfig,
>                                       priv->monJSON, priv->qemuCaps,
>                                       migrateFrom, stdin_fd, snapshot, vmop,
>                                       &buildCommandLineCallbacks, false,
>                                       qemuCheckFips(),
>                                       priv->autoNodeset,
> -                                     &nnicindexes, &nicindexes)))
> +                                     &nnicindexes, &nicindexes))) {
> +        virObjectLock(vm);
>          goto cleanup;
> +    }
> +    virObjectLock(vm);

Why do you need to unlock the object? The VM is starting at this point
so you won't be able to save any time since APIs will either be blocked
by a job or by the fact that the VM was not started.

Would you care to explain what are the benefits of doing this?

NACK unless you provide a convincing example where this would help.

Peter
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