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Re: [PATCH 4/7] kprobes: Support probing module __exit function
- From: Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>
- To: Andrew Morton <akpm at linux-foundation dot org>
- Cc: Masami Hiramatsu <mhiramat at redhat dot com>, jkenisto at us dot ibm dot com, davem at davemloft dot net, rusty at rustcorp dot com dot au, linux-kernel at vger dot kernel dot org, systemtap at sources dot redhat dot com
- Date: Fri, 14 Nov 2008 10:21:35 +0530
- Subject: Re: [PATCH 4/7] kprobes: Support probing module __exit function
- References: <4919F19A.9050904@redhat.com> <20081113162739.5e871fab.akpm@linux-foundation.org>
- Reply-to: ananth at in dot ibm dot com
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@redhat.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