[libvirt] [PATCH 08/12] libxl: Use atomic ops for driver->nactive
Jim Fehlig
jfehlig at suse.com
Tue Sep 3 23:18:03 UTC 2013
Michal Privoznik wrote:
> On 30.08.2013 23:46, Jim Fehlig wrote:
>
>> Signed-off-by: Jim Fehlig <jfehlig at suse.com>
>> ---
>> src/libxl/libxl_conf.h | 2 +-
>> src/libxl/libxl_driver.c | 10 ++++------
>> 2 files changed, 5 insertions(+), 7 deletions(-)
>>
>> diff --git a/src/libxl/libxl_conf.h b/src/libxl/libxl_conf.h
>> index e3875ba..83bb6b9 100644
>> --- a/src/libxl/libxl_conf.h
>> +++ b/src/libxl/libxl_conf.h
>> @@ -90,7 +90,7 @@ struct _libxlDriverPrivate {
>> * then lockless thereafter */
>> libxlDriverConfigPtr config;
>>
>> - size_t nactive;
>> + unsigned int nactive;
>>
>> virStateInhibitCallback inhibitCallback;
>> void *inhibitOpaque;
>> diff --git a/src/libxl/libxl_driver.c b/src/libxl/libxl_driver.c
>> index e604899..7615cdd 100644
>> --- a/src/libxl/libxl_driver.c
>> +++ b/src/libxl/libxl_driver.c
>> @@ -50,6 +50,7 @@
>> #include "virstring.h"
>> #include "virsysinfo.h"
>> #include "viraccessapicheck.h"
>> +#include "viratomic.h"
>>
>> #define VIR_FROM_THIS VIR_FROM_LIBXL
>>
>> @@ -265,8 +266,7 @@ libxlVmCleanup(libxlDriverPrivatePtr driver,
>> virDomainObjSetState(vm, VIR_DOMAIN_SHUTOFF, reason);
>> }
>>
>> - driver->nactive--;
>> - if (!driver->nactive && driver->inhibitCallback)
>> + if (virAtomicIntDecAndTest(&driver->nactive) && driver->inhibitCallback)
>> driver->inhibitCallback(false, driver->inhibitOpaque);
>>
>> if ((vm->def->ngraphics == 1) &&
>> @@ -655,9 +655,8 @@ libxlVmStart(libxlDriverPrivatePtr driver, virDomainObjPtr vm,
>> if (virDomainSaveStatus(driver->xmlopt, cfg->stateDir, vm) < 0)
>> goto error;
>>
>> - if (!driver->nactive && driver->inhibitCallback)
>> + if (virAtomicIntInc(&driver->nactive) && driver->inhibitCallback)
>> driver->inhibitCallback(true, driver->inhibitOpaque);
>>
>
> Not exactly the same as previous code. Previously, the callback was
> called iff nactive == 0; However, with your change the callback is
> invoked each time the control gets to the 'if' (as virAtomicIntInc()
> returns the *new* value after the increment). I think we want this to be:
>
> if (virAtomicIntInc(&driver->nactive) == 1 && driver->inhibitCallback)
>
Opps, thanks for catching that. I've fixed both instances you pointed out.
Regards,
Jim
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