netdev - Re: [PATCH v2 08/13] tracing: Improve panic/die notifiers

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Message-ID: <YvuwUAGi6PvY5kmR@rowland.harvard.edu>
Date:   Tue, 16 Aug 2022 10:57:20 -0400
From:   Alan Stern <stern@...land.harvard.edu>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     "Guilherme G. Piccoli" <gpiccoli@...lia.com>,
        akpm@...ux-foundation.org, bhe@...hat.com, pmladek@...e.com,
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        will@...nel.org, Sergei Shtylyov <sergei.shtylyov@...il.com>
Subject: Re: [PATCH v2 08/13] tracing: Improve panic/die notifiers

On Tue, Aug 16, 2022 at 10:14:45AM -0400, Steven Rostedt wrote:
> On Tue, 19 Jul 2022 16:53:21 -0300
> "Guilherme G. Piccoli" <gpiccoli@...lia.com> wrote:
> 
> 
> Sorry for the late review, but this fell to the bottom of my queue :-/
> 
> > +/*
> > + * The idea is to execute the following die/panic callback early, in order
> > + * to avoid showing irrelevant information in the trace (like other panic
> > + * notifier functions); we are the 2nd to run, after hung_task/rcu_stall
> > + * warnings get disabled (to prevent potential log flooding).
> > + */
> > +static int trace_die_panic_handler(struct notifier_block *self,
> > +				unsigned long ev, void *unused)
> > +{
> > +	if (!ftrace_dump_on_oops)
> > +		goto out;
> > +
> > +	if (self == &trace_die_notifier && ev != DIE_OOPS)
> > +		goto out;
> 
> I really hate gotos that are not for clean ups.
> 
> > +
> > +	ftrace_dump(ftrace_dump_on_oops);
> > +
> > +out:
> > +	return NOTIFY_DONE;
> > +}
> > +
> 
> Just do:
> 
> static int trace_die_panic_handler(struct notifier_block *self,
> 				unsigned long ev, void *unused)
> {
> 	if (!ftrace_dump_on_oops)
> 		return NOTIFY_DONE;
> 
> 	/* The die notifier requires DIE_OOPS to trigger */
> 	if (self == &trace_die_notifier && ev != DIE_OOPS)
> 		return NOTIFY_DONE;
> 
> 	ftrace_dump(ftrace_dump_on_oops);
> 
> 	return NOTIFY_DONE;
> }

Or better yet:

	if (ftrace_dump_on_oops) {

		/* The die notifier requires DIE_OOPS to trigger */
		if (self != &trace_die_notifier || ev == DIE_OOPS)
			ftrace_dump(ftrace_dump_on_oops);
	}
	return NOTIFY_DONE;

Alan Stern

> Thanks,
> 
> Other than that, Acked-by: Steven Rostedt (Google) <rostedt@...dmis.org>
> 
> -- Steve