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

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Message-ID: <20181204124333.00f4c5ee@vmware.local.home>
Date:   Tue, 4 Dec 2018 12:43:33 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Masami Hiramatsu <mhiramat@...nel.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 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?

-- 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;
>  }