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

From: Russell King - ARM Linux
Date: Wed Oct 24 2018 - 04:58:45 EST

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.

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