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

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Message-ID: <20220816115249.66cf8f15@gandalf.local.home>
Date:   Tue, 16 Aug 2022 11:52:49 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Alan Stern <stern@...land.harvard.edu>
Cc:     "Guilherme G. Piccoli" <gpiccoli@...lia.com>,
        akpm@...ux-foundation.org, bhe@...hat.com, pmladek@...e.com,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
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        tglx@...utronix.de, vgoyal@...hat.com, vkuznets@...hat.com,
        will@...nel.org, Sergei Shtylyov <sergei.shtylyov@...il.com>
Subject: Re: [PATCH v2 08/13] tracing: Improve panic/die notifiers

On Tue, 16 Aug 2022 10:57:20 -0400
Alan Stern <stern@...land.harvard.edu> wrote:

> > 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;
> 

That may be more consolidated but less easy to read and follow. This is far
from a fast path.

As I maintain this bike-shed, I prefer the one I suggested ;-)

-- Steve