linux-kernel - Re: [PATCH 4/7] kprobes: Support probing module _

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Message-ID: <20081114045135.GA3141@in.ibm.com>
Date:	Fri, 14 Nov 2008 10:21:35 +0530
From:	Ananth N Mavinakayanahalli <ananth@...ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Masami Hiramatsu <mhiramat@...hat.com>, jkenisto@...ibm.com,
	davem@...emloft.net, rusty@...tcorp.com.au,
	linux-kernel@...r.kernel.org, systemtap@...rces.redhat.com
Subject: Re: [PATCH 4/7] kprobes: Support probing module __exit function

On Thu, Nov 13, 2008 at 04:27:39PM -0800, Andrew Morton wrote:
> On Tue, 11 Nov 2008 15:56:58 -0500
> Masami Hiramatsu <mhiramat@...hat.com> wrote:
> 
> > @@ -69,9 +69,6 @@ struct kprobe {
> >  	/* list of kprobes for multi-handler support */
> >  	struct list_head list;
> > 
> > -	/* Indicates that the corresponding module has been ref counted */
> > -	unsigned int mod_refcounted;
> > -
> >  	/*count the number of times this probe was temporarily disarmed */
> >  	unsigned long nmissed;
> > 
> > @@ -103,8 +100,19 @@ struct kprobe {
> > 
> >  	/* copy of the original instruction */
> >  	struct arch_specific_insn ainsn;
> > +
> > +	/* Indicates various status flags */
> > +	u32 flags;
> >  };
> > 
> > +/* Kprobe status flags */
> > +#define KPROBE_FLAG_GONE	1 /* breakpoint has already gone */
> > +
> > +static inline int kprobe_gone(struct kprobe *p)
> > +{
> > +	return p->flags & KPROBE_FLAG_GONE;
> > +}
> 
> If we're not going to use atomic bitops on kprobe.flags then
> modifications to that member will require that the caller hold a lock. 
> The comment above that member should describe its locking protocol.  It
> seems that it is kprobe_mutex, so...
> 
> --- a/include/linux/kprobes.h~kprobes-support-probing-module-__exit-function-fix
> +++ a/include/linux/kprobes.h
> @@ -101,7 +101,7 @@ struct kprobe {
>  	/* copy of the original instruction */
>  	struct arch_specific_insn ainsn;
> 
> -	/* Indicates various status flags */
> +	/* Indicates various status flags.  Protected by kprobe_mutex. */
>  	u32 flags;
>  };
> 
> _
> 
> 
> yes?

Right, setting and resetting is done under the kprobe_mutex.

Ananth
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