[libvirt] [PATCH 08/12] libxl: Use atomic ops for driver->nactive

[Jim Fehlig]

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