linux-kernel - Re: [PATCH RT] Align rt_mutex inlining with upstream behavior

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Message-ID: <20170210182807.6gzs3xn3ga727xsb@linutronix.de>
Date:   Fri, 10 Feb 2017 19:28:07 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Andy Ritger <aritger@...dia.com>
Cc:     Alex Goins <agoins@...dia.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-rt-users@...r.kernel.org, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH RT] Align rt_mutex inlining with upstream behavior

On 2017-02-10 10:09:29 [-0800], Andy Ritger wrote:
> Is the
> 
>     WARN_ON(rt_mutex_is_locked(lock));
> 
> in rt_mutex_destroy() valuable in non-CONFIG_DEBUG_MUTEXES kernels,
> such that it would be better to always call it, and not noop away mutex_destroy()
> non-CONFIG_DEBUG_MUTEXES kernels?  I thought that was your objection to
> Alex's original patch.

It kind of was…
So first I removed the GPL symbol. Then I wasn't too happy about it
especially since it was not introduced as part of RT. So I reverted that
changed and aligned with mainline behaviour (the mutex_rt.h hunk). But
then I noticed that with CONFIG_DEBUG_MUTEXES=n and
CONFIG_DEBUG_RT_MUTEXES=y we still have a regression compared to !RT and
this was the initial motivation to fix things.
Then I got curious why mutex_lock() (which is essential rt_mutex_lock())
works and noticed the wrapper around it. And while looking at it I
decided to go back to strip the GPL part from export symbol instead of
adding a wrapper. And here I am.
Then I was looking at the patch and decided to align with mainline (and
keep that one hunk) in case Ingo ask for his GPL symbol.

> Thanks,
> - Andy
Sebastian