linux-kernel - Re: [PATCH RT v2] arm64: fpsimd: use a local_lock() in addition to local_bh

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Date:   Wed, 18 Jul 2018 11:24:48 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Dave Martin <Dave.Martin@....com>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        linux-rt-users@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Mike Galbraith <efault@....de>,
        Will Deacon <will.deacon@....com>,
        linux-kernel@...r.kernel.org, tglx@...utronix.de,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH RT v2] arm64: fpsimd: use a local_lock() in addition to
 local_bh_disable()

On 2018-07-18 11:12:10 [+0200], To Dave Martin wrote:
> > > -	if (may_use_simd()) {
> > > +	if (!IS_ENABLED(CONFIG_PREEMPT_RT_BASE) && may_use_simd()) {
> > 
> > I suspect this is wrong -- see comments on the commit message.

I'm sorry, I pressed send too early, I was aiming for the draft folder.
So yes, based on that EFI that might be interruptible, let me try to
look at the initial issue again and maybe I get another idea how to deal
with this.
One question: If EFI is interruptible that means, we call into EFI - how
do we get out? Does EFI enable interrupts and the kernel receives an
interrupt and treats this EFI call like a regular context switch?

> > >  		kernel_neon_begin();
> > >  	} else {
> > 
> > [...]
> > 
> > Cheers
> > ---Dave

Sebastian