linux-kernel - Re: [PATCH] KVM: arm64: vgic: declear local variable 'flags' before for loop starts

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Message-ID: <87eed7tk24.wl-maz@kernel.org>
Date:   Sat, 12 Jun 2021 12:10:43 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Austin Kim <austindh.kim@...il.com>
Cc:     james.morse@....com, alexandru.elisei@....com,
        suzuki.poulose@....com, catalin.marinas@....com, will@...nel.org,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org, austin.kim@....com
Subject: Re: [PATCH] KVM: arm64: vgic: declear local variable 'flags' before for loop starts

On Sat, 12 Jun 2021 12:00:14 +0100,
Austin Kim <austindh.kim@...il.com> wrote:
> 
> From: Austin Kim <austin.kim@....com>
> 
> Normally local variable 'flags' is defined out of for loop,
> when 'flags' is used as the second parameter in a call to
> spinlock_irq[save/restore] function.
> 
> So it had better declear local variable 'flags' ahead of for loop.

Why better? Reducing the scope of a variable is in general good
practice. Do you see any material advantage in moving this variable
out of the loop? Does the compiler generate better code?

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.