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SubjectRe: [PATCH] markers: comment marker_synchronize_unregister() on data dependency
* Wu Fengguang (fengguang.wu@intel.com) wrote:
> On Thu, Nov 27, 2008 at 10:00:03AM +0200, Mathieu Desnoyers wrote:
> > * Wu Fengguang (fengguang.wu@intel.com) wrote:
> > > +
> > > +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
>
> That's much better!
>
> With your comments I'd assume you reviewed this patch ;-)
>
> Thanks,
> 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.
>
> Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
> Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
> Signed-off-by: Wu Fengguang <wfg@linux.intel.com>

It looks good to me, thanks!

Acked-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>


> ---
> diff --git a/Documentation/markers.txt b/Documentation/markers.txt
> index 089f613..d9569a3 100644
> --- a/Documentation/markers.txt
> +++ b/Documentation/markers.txt
> @@ -51,11 +51,16 @@ 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 between probe unregistration and
> +the first occurrence of
> +- the end of 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..5f12d1b 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


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