linux-kernel - Re: [PATCH 3/6] sched: Extract __schedule

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Message-ID: <20230816113945.GA639355@lorien.usersys.redhat.com>
Date:   Wed, 16 Aug 2023 07:39:45 -0400
From:   Phil Auld <pauld@...hat.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Peter Zijlstra <peterz@...radead.org>, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, bsegall@...gle.com,
        boqun.feng@...il.com, swood@...hat.com, bristot@...hat.com,
        dietmar.eggemann@....com, mingo@...hat.com, jstultz@...gle.com,
        juri.lelli@...hat.com, mgorman@...e.de, rostedt@...dmis.org,
        vschneid@...hat.com, vincent.guittot@...aro.org,
        longman@...hat.com, will@...nel.org
Subject: Re: [PATCH 3/6] sched: Extract __schedule_loop()

On Wed, Aug 16, 2023 at 12:01:54PM +0200 Sebastian Andrzej Siewior wrote:
> On 2023-08-15 18:33:01 [-0400], Phil Auld wrote:
> > > --- a/kernel/sched/core.c
> > > +++ b/kernel/sched/core.c
> > > @@ -6787,16 +6787,21 @@ static void sched_update_worker(struct t
> > >  	}
> > >  }
> > >  
> > > -asmlinkage __visible void __sched schedule(void)
> > > +static __always_inline void __schedule_loop(unsigned int sched_mode)
> > 
> > I think this needs __sched or it's the only thing that ever shows up
> > in wchan. E.g.
> > 
> >   16995 0 bash     S __schedule_loop.constprop.0
> 
> I don't see __schedule_loop in my RT and !RT build. I tried gcc and
> clang.
>

I do.  Admittedly I'm not an expert in how the wchan unwinding works but
we have a slightly older version of this patch in our kernel (schedule_loop
not __schedule_loop). When I added __sched it fixed it.   Maybe there
is something else but that seemed pretty obvious. 


/* Attach to any functions which should be ignored in wchan output. */
#define __sched		__section(".sched.text")

I can't explain why you are not seeing it.


Cheers,
Phil


> Sebastian
> 

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