From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lai Jiangshan Subject: Re: [PATCH] markers: comment marker_synchronize_unregister() on data dependency Date: Thu, 27 Nov 2008 09:23:06 +0800 Message-ID: <492DF67A.8090006@cn.fujitsu.com> References: <20081126123652.GA9446@localhost> <20081126124608.GA22504@Krystal> <20081126130847.GA20988@localhost> <20081127010553.GA11182@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Mathieu Desnoyers , LKML , Ingo Molnar , Avi Kivity , "kvm@vger.kernel.org" , "Paul E. McKenney" , Andrew Morton , Nick Piggin To: Wu Fengguang Return-path: Received: from cn.fujitsu.com ([222.73.24.84]:65018 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751793AbYK0B0G (ORCPT ); Wed, 26 Nov 2008 20:26:06 -0500 In-Reply-To: <20081127010553.GA11182@localhost> Sender: kvm-owner@vger.kernel.org List-ID: 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 > Cc: Mathieu Desnoyers > Signed-off-by: Wu Fengguang > --- > 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? It's every good job, thank you. Reviewed-by: Lai Jiangshan > + * to ensure the code and data are valid for any possibly running probes. > */ > #define marker_synchronize_unregister() synchronize_sched() > > > >