linux-kernel - Re: [PATCH RT] arm64: fpsimd: use a local_lock() in addition to local_bh

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Message-ID: <20180522132429.6f1dcf92@gandalf.local.home>
Date:   Tue, 22 May 2018 13:24:29 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH RT] arm64: fpsimd: use a local_lock() in addition to
 local_bh_disable()

On Tue, 22 May 2018 19:21:16 +0200
Sebastian Andrzej Siewior <bigeasy@...utronix.de> wrote:

> On 2018-05-22 13:10:04 [-0400], Steven Rostedt wrote:
> > On Thu, 17 May 2018 14:40:06 +0200
> > Sebastian Andrzej Siewior <bigeasy@...utronix.de> wrote:
> >   
> > > +static DEFINE_LOCAL_IRQ_LOCK(fpsimd_lock);
> > >  /*
> > >   * Update current's FPSIMD/SVE registers from thread_struct.
> > >   *
> > > @@ -594,6 +595,7 @@ int sve_set_vector_length(struct task_struct *task,
> > >  	 * non-SVE thread.
> > >  	 */
> > >  	if (task == current) {
> > > +		local_lock(fpsimd_lock);
> > >  		local_bh_disable();  
> > 
> > I'm surprised that we don't have a "local_lock_bh()"?  
> 
> right. Like the last time when we introduced a global lock with no
> locking context? 
> 

I meant, we could have local_lock_bh(fpsimd_lock); that would turn into
a local_bh_disable() when !PREEMPT_RT.

-- Steve