Messages in this thread | | | Date | Thu, 27 Nov 2008 03:00:03 -0500 | From | Mathieu Desnoyers <> | Subject | Re: [PATCH] markers: comment marker_synchronize_unregister() on data dependency |
| |
* Wu Fengguang (fengguang.wu@intel.com) wrote: > On Thu, Nov 27, 2008 at 03:23:06AM +0200, Lai Jiangshan wrote: > > Wu Fengguang wrote: > > > [updated patch to include Documentation/markers.txt changes] > > > > > > Add document and comments on marker_synchronize_unregister(): it > > > should be called before freeing resources that the probes depend on. > > > > > > Based on comments from Lai Jiangshan and Mathieu Desnoyers. > > > > > > Cc: Lai Jiangshan <laijs@cn.fujitsu.com> > > > Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> > > > Signed-off-by: Wu Fengguang <wfg@linux.intel.com> > > > --- > > > diff --git a/Documentation/markers.txt b/Documentation/markers.txt > > > index 089f613..8bf6afe 100644 > > > --- a/Documentation/markers.txt > > > +++ b/Documentation/markers.txt > > > @@ -51,11 +51,15 @@ to call) for the specific marker through marker_probe_register() and can be > > > activated by calling marker_arm(). Marker deactivation can be done by calling > > > marker_disarm() as many times as marker_arm() has been called. Removing a probe > > > is done through marker_probe_unregister(); it will disarm the probe. > > > -marker_synchronize_unregister() must be called before the end of the module exit > > > -function to make sure there is no caller left using the probe. This, and the > > > -fact that preemption is disabled around the probe call, make sure that probe > > > -removal and module unload are safe. See the "Probe example" section below for a > > > -sample probe module. > > > + > > > +marker_synchronize_unregister() must be called before the first occurrence of > > > +- the end of the module exit function, > > > + to make sure there is no caller left using the probe; > > > +- the free of any resource used by the probes, > > > + to make sure the probes wont be accessing destructed data. > > > +This, and the fact that preemption is disabled around the probe call, make sure > > > +that probe removal and module unload are safe. See the "Probe example" section > > > +below for a sample probe module. > > > > > > The marker mechanism supports inserting multiple instances of the same marker. > > > Markers can be put in inline functions, inlined static functions, and > > > diff --git a/include/linux/marker.h b/include/linux/marker.h > > > index 889196c..32ce4f2 100644 > > > --- a/include/linux/marker.h > > > +++ b/include/linux/marker.h > > > @@ -162,8 +162,10 @@ extern void *marker_get_private_data(const char *name, marker_probe_func *probe, > > > > > > /* > > > * marker_synchronize_unregister must be called between the last marker probe > > > - * unregistration and the end of module exit to make sure there is no caller > > > - * executing a probe when it is freed. > > > + * unregistration and the first one of > > > + * - the end of module exit function > > > + * - the free of any resource used by the probes > > > > Does "destruction" contain the meaning of "free" and other destruction behavior? > > Ahh, better to use "invalid data" instead of "destructed data"? > > > It's every good job, thank you. > > > > Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com> > > Thank you, > Fengguang > --- > markers: comment marker_synchronize_unregister() on data dependency > > Add document and comments on marker_synchronize_unregister(): it > should be called before freeing resources that the probes depend on. > > Based on comments from Lai Jiangshan and Mathieu Desnoyers. > > Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> > Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com> > Signed-off-by: Wu Fengguang <wfg@linux.intel.com> > --- > diff --git a/Documentation/markers.txt b/Documentation/markers.txt > index 089f613..8bf6afe 100644 > --- a/Documentation/markers.txt > +++ b/Documentation/markers.txt > @@ -51,11 +51,15 @@ to call) for the specific marker through marker_probe_register() and can be > activated by calling marker_arm(). Marker deactivation can be done by calling > marker_disarm() as many times as marker_arm() has been called. Removing a probe > is done through marker_probe_unregister(); it will disarm the probe. > -marker_synchronize_unregister() must be called before the end of the module exit > -function to make sure there is no caller left using the probe. This, and the > -fact that preemption is disabled around the probe call, make sure that probe > -removal and module unload are safe. See the "Probe example" section below for a > -sample probe module. > + > +marker_synchronize_unregister() must be called before the first occurrence of
You should probably say
".. must be called between probe unregistration and the first occurence of..."
Mathieu
> +- the end of the module exit function, > + to make sure there is no caller left using the probe; > +- the free of any resource used by the probes, > + to make sure the probes wont be accessing invalid data. > +This, and the fact that preemption is disabled around the probe call, make sure > +that probe removal and module unload are safe. See the "Probe example" section > +below for a sample probe module. > > The marker mechanism supports inserting multiple instances of the same marker. > Markers can be put in inline functions, inlined static functions, and > diff --git a/include/linux/marker.h b/include/linux/marker.h > index 889196c..32ce4f2 100644 > --- a/include/linux/marker.h > +++ b/include/linux/marker.h > @@ -162,8 +162,10 @@ extern void *marker_get_private_data(const char *name, marker_probe_func *probe, > > /* > * marker_synchronize_unregister must be called between the last marker probe > - * unregistration and the end of module exit to make sure there is no caller > - * executing a probe when it is freed. > + * unregistration and the first one of > + * - the end of module exit function > + * - the free of any resource used by the probes > + * to ensure the code and data are valid for any possibly running probes. > */ > #define marker_synchronize_unregister() synchronize_sched() >
-- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
| |