linux-kernel - Re: [PATCH v3 0/7] include: add setbits32/clrbits32/clrsetbits32/setbits64/clrbits64/clrsetbits64

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Message-ID: <20181024085700.GR30658@n2100.armlinux.org.uk>
Date:   Wed, 24 Oct 2018 09:57:00 +0100
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Corentin Labbe <clabbe@...libre.com>
Cc:     Gilles.Muller@...6.fr, Julia.Lawall@...6.fr, agust@...x.de,
        airlied@...ux.ie, alexandre.torgue@...com, alistair@...ple.id.au,
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        galak@...nel.crashing.org, joabreu@...opsys.com,
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        mpe@...erman.id.au, mporter@...nel.crashing.org,
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Subject: Re: [PATCH v3 0/7] include: add
 setbits32/clrbits32/clrsetbits32/setbits64/clrbits64/clrsetbits64

On Wed, Oct 24, 2018 at 07:35:46AM +0000, Corentin Labbe wrote:
> This patchset adds a new set of functions which are open-coded in lot of
> place.
> Basicly the pattern is always the same, "read, modify a bit, write"
> some driver and the powerpc arch already have thoses pattern them as functions. (like ahci_sunxi.c or dwmac-meson8b)

The advantage of them being open-coded is that it's _obvious_ to the
reviewer that there is a read-modify-write going on which, in a multi-
threaded environment, may need some locking (so it should trigger a
review of the locking around that code.)

With it hidden inside a helper which has no locking itself, it becomes
much easier to pass over in review, which means that races are much
more likely to go unspotted - and that is bad news.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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