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

On 30.08.2013 23:46, Jim Fehlig wrote: > Signed-off-by: Jim Fehlig <jfehlig(a)suse.com&gt; > --- > 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)