[libvirt] [PATCH] qemuDomainSendKey: Relax the qemu driver locking

[Viktor Mihajlovski]

On 01/24/2013 10:41 AM, Michal Privoznik wrote:
> Currently, there is no reason to hold qemu driver locked
> throughout whole API execution. Moreover, we can use the
> new qemuDomObjFromDomain() internal API to lookup domain then.
> ---
>   src/qemu/qemu_driver.c | 16 ++++------------
>   1 file changed, 4 insertions(+), 12 deletions(-)
>
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index 6d4c1e9..100f10b 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -2407,19 +2407,12 @@ static int qemuDomainSendKey(virDomainPtr domain,
>           }
>       }
>
> -    qemuDriverLock(driver);
> -    vm = virDomainFindByUUID(&driver->domains, domain->uuid);
> -    if (!vm) {
> -        char uuidstr[VIR_UUID_STRING_BUFLEN];
> -        virUUIDFormat(domain->uuid, uuidstr);
> -        virReportError(VIR_ERR_NO_DOMAIN,
> -                       _("no domain with matching uuid '%s'"), uuidstr);
> +    if (!(vm = qemuDomObjFromDomain(domain)))
>           goto cleanup;
> -    }
>
>       priv = vm->privateData;
>
> -    if (qemuDomainObjBeginJobWithDriver(driver, vm, QEMU_JOB_MODIFY) < 0)
> +    if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_MODIFY) < 0)
>           goto cleanup;
>
>       if (!virDomainObjIsActive(vm)) {
> @@ -2428,9 +2421,9 @@ static int qemuDomainSendKey(virDomainPtr domain,
>           goto endjob;
>       }
>
> -    qemuDomainObjEnterMonitorWithDriver(driver, vm);
> +    qemuDomainObjEnterMonitor(driver, vm);
>       ret = qemuMonitorSendKey(priv->mon, holdtime, keycodes, nkeycodes);
> -    qemuDomainObjExitMonitorWithDriver(driver, vm);
> +    qemuDomainObjExitMonitor(driver, vm);
>
>   endjob:
>       if (qemuDomainObjEndJob(driver, vm) == 0)
> @@ -2439,7 +2432,6 @@ endjob:
>   cleanup:
>       if (vm)
>           virObjectUnlock(vm);
> -    qemuDriverUnlock(driver);
>       return ret;
>   }
>
Formally this looks good and works on my system, so I would be fine with
it.
I am just wondering what the criteria are for holding a long-term lock 
vs a short-time on. I.e. why would DomainSendKey be relaxed while
DomainInjectNMI keeps the driver lock?

-- 

Mit freundlichen Grüßen/Kind Regards
    Viktor Mihajlovski

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