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

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Message-ID: <20180724135706.nn2exgz53o7jfwm4@linutronix.de>
Date:   Tue, 24 Jul 2018 15:57:06 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Dave Martin <Dave.Martin@....com>, 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 2018-07-24 09:46:23 [-0400], Steven Rostedt wrote:
> > Unfortunately yes.
> 
> Then we need to find another solution, because this is way too ugly and
> as Dave said, fragile to keep.

Yes. I have something new where Mike said it works (while this causes
Mike's gcc to segfault). Need to test this myself…

> How does local_lock_bh() do a +3 (not seeing it in the code). And

get_local_var() +1
spin_lock_bh() +2 because
	local_bh_disable() +1
	spin_lock() +1

Sebastian