linux-kernel - Re: [PATCH 08/12] unwind: Simplify unwind_user

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Message-ID: <20251020101751.GL3419281@noisy.programming.kicks-ass.net>
Date: Mon, 20 Oct 2025 12:17:51 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: jpoimboe@...nel.org, rostedt@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/12] unwind: Simplify unwind_user_faultable()

On Wed, Oct 01, 2025 at 11:40:53AM -0400, Steven Rostedt wrote:
> On Wed, 24 Sep 2025 09:59:56 +0200
> Peter Zijlstra <peterz@...radead.org> wrote:
> 
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> > ---
> >  kernel/unwind/deferred.c |    6 ++----
> >  1 file changed, 2 insertions(+), 4 deletions(-)
> > 
> > --- a/kernel/unwind/deferred.c
> > +++ b/kernel/unwind/deferred.c
> > @@ -128,17 +128,15 @@ int unwind_user_faultable(struct unwind_
> >  
> >  	cache = info->cache;
> >  	trace->entries = cache->entries;
> > -
> > -	if (cache->nr_entries) {
> > +	trace->nr = cache->nr_entries;
> > +	if (trace->nr) {
> >  		/*
> >  		 * The user stack has already been previously unwound in this
> >  		 * entry context.  Skip the unwind and use the cache.
> >  		 */
> > -		trace->nr = cache->nr_entries;
> >  		return 0;
> >  	}
> 
> Could we turn the above into:
> 
> 	/*
> 	 * If the user stack has already been previously unwound in this
> 	 * entry context.  Skip the unwind and use the cache.
> 	 */
> 	if (trace->nr)
> 		return 0;
> 
> So we could remove the squiggly brackets?

This tarriff nonsense must be really bad if you're re-cycling them so
aggressively :-)

Sure, done.