linux-kernel - Re: [PATCH 2/8] radix-tree: Use local

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Message-ID: <20200520020516.GB16070@bombadil.infradead.org>
Date:   Tue, 19 May 2020 19:05:16 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>, Will Deacon <will@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 2/8] radix-tree: Use local_lock for protection

On Tue, May 19, 2020 at 04:54:53PM -0400, Steven Rostedt wrote:
> On Tue, 19 May 2020 13:45:45 -0700
> Matthew Wilcox <willy@...radead.org> wrote:
> 
> > On Tue, May 19, 2020 at 10:19:06PM +0200, Sebastian Andrzej Siewior wrote:
> > > The radix-tree and idr preload mechanisms use preempt_disable() to protect
> > > the complete operation between xxx_preload() and xxx_preload_end().
> > > 
> > > As the code inside the preempt disabled section acquires regular spinlocks,
> > > which are converted to 'sleeping' spinlocks on a PREEMPT_RT kernel and
> > > eventually calls into a memory allocator, this conflicts with the RT
> > > semantics.
> > > 
> > > Convert it to a local_lock which allows RT kernels to substitute them with
> > > a real per CPU lock. On non RT kernels this maps to preempt_disable() as
> > > before, but provides also lockdep coverage of the critical region.
> > > No functional change.  
> > 
> > I don't seem to have a locallock.h in my tree.  Where can I find more
> > information about it?
> 
> PATCH 1 ;-)

... this is why we have the convention to cc everybody on all the patches.

>  https://lore.kernel.org/r/20200519201912.1564477-1-bigeasy@linutronix.de
> 
> With lore and b4, it should now be easy to get full patch series.

Thats asking too much of the random people cc'd on random patches.
What is b4 anyway?