linux-kernel - Re: [PATCH v2 01/12] tracing/uprobes: Add busy check when cleanup all uprobes

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Date:   Fri, 7 Dec 2018 11:19:57 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Tom Zanussi <tom.zanussi@...ux.intel.com>,
        Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
Subject: Re: [PATCH v2 01/12] tracing/uprobes: Add busy check when cleanup
 all uprobes

On Tue, 4 Dec 2018 12:43:33 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Mon,  5 Nov 2018 18:00:15 +0900
> Masami Hiramatsu <mhiramat@...nel.org> wrote:
> 
> > Add a busy check loop in cleanup_all_probes() before
> > trying to remove all events in uprobe_events as same as
> > kprobe_events does.
> > 
> > Without this change, writing null to uprobe_events will
> > try to remove events but if one of them is enabled, it
> > stopped there but some of events are already cleared.
> > 
> > With this change, writing null to uprobe_events make
> > sure all events are not enabled before removing events.
> > So, it clears all events, or return an error (-EBUSY)
> > with keeping all events.
> > 
> 
> Hmm, should this patch be marked as stable?

Hmm, OK, let this go to stable. Since anyway, this will cause
a wired result on uprobe_events from user point of view.

Thank you!

> 
> -- Steve
> 
> > Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> > ---
> >  kernel/trace/trace_uprobe.c |    7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
> > index 31ea48eceda1..b708e4ff7ea7 100644
> > --- a/kernel/trace/trace_uprobe.c
> > +++ b/kernel/trace/trace_uprobe.c
> > @@ -587,12 +587,19 @@ static int cleanup_all_probes(void)
> >  	int ret = 0;
> >  
> >  	mutex_lock(&uprobe_lock);
> > +	/* Ensure no probe is in use. */
> > +	list_for_each_entry(tu, &uprobe_list, list)
> > +		if (trace_probe_is_enabled(&tu->tp)) {
> > +			ret = -EBUSY;
> > +			goto end;
> > +		}
> >  	while (!list_empty(&uprobe_list)) {
> >  		tu = list_entry(uprobe_list.next, struct trace_uprobe, list);
> >  		ret = unregister_trace_uprobe(tu);
> >  		if (ret)
> >  			break;
> >  	}
> > +end:
> >  	mutex_unlock(&uprobe_lock);
> >  	return ret;
> >  }
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>