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Date:   Sat, 22 Apr 2023 17:07:56 +0200
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        stable@vger.kernel.org, Mel Gorman <mgorman@techsingularity.net>,
        Jan Kara <jack@suse.cz>
Subject: Re: [PATCH] rtmutex: Add acquire semantics for rtmutex lock
 acquisition slow path
Message-ID: <2023042247-glandular-litigate-413e@gregkh>
References: <20230418154315.9PD52J2N@linutronix.de>
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On Fri, Apr 21, 2023 at 06:33:30PM +0200, Thomas Gleixner wrote:
> On Fri, Apr 21 2023 at 18:09, Sebastian Andrzej Siewior wrote:
> > On 2023-04-21 17:30:24 [+0200], Thomas Gleixner wrote:
> >> >> > The out-of-tree RT patches make extensive use of the code. Since it is
> >> >> > upstream code, I assumed it should go via the official stable trees.
> >> >> > Without RT, the code is limited the rt_mutex_lock() used by I2C and the
> >> >> > RCU booster-mutex.
> >> >> 
> >> >> Which is a reason to route it through the upstream stable trees, no?
> >> >
> >> > I do not understand.  Why would we take a patch in the stable tree
> >> > because an out-of-tree change requires it?
> >> 
> >> The change is to the rtmutex core which _IS_ used in tree by futex, RCU
> >> and some drivers.
> >
> > not back stab but to clarify: futex does not use the annotation (it does
> > not use the fastpath) but RCU-boosting _and_ I2C-bus code does use it.
> 
> Futex requires it too, really. The patch is about the slowpath, no?
> 
> 

Ok, sorry, I was confused, now queued up.

greg k-h