linux-kernel - Re: [PATCH v2] locking/rtmutex: Use acquire/release semantics

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Message-ID: <alpine.DEB.2.11.1509292256010.4500@nanos>
Date:	Tue, 29 Sep 2015 22:57:32 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Davidlohr Bueso <dave@...olabs.net>
cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Will Deacon <will.deacon@....com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH v2] locking/rtmutex: Use acquire/release semantics

On Mon, 28 Sep 2015, Davidlohr Bueso wrote:
> On Sun, 27 Sep 2015, Thomas Gleixner wrote:
> > That changelog is not really helpful if someone is going to look at it
> > half a year from now who doesn't have the background of the discussion
> > leading to these changes.
> 
> Ok, how does the following sound?
> 
> ""
> As of 654672d4ba1 (locking/atomics: Add _{acquire|release|relaxed}() variants
> of some atomic operations) and 6d79ef2d30e (locking, asm-generic: Add
> _{relaxed|acquire|release}() variants for 'atomic_long_t'), weakly ordered
> archs can benefit from more relaxed use of barriers when locking and
> unlocking,
> instead of regular full barrier semantics. While currently only arm64 supports
> such optimizations, updating corresponding locking primitives serves for other
> archs to immediately benefit as well, once the necessary machinery is
> implemented
> of course.
> ""
> 
> It's not _that_ different from the original changelong, but it should allow
> future readers to at least be able to easily see the context of where the
> changes come from. I don't think it's of much use going into the actual code
> changes as they are pretty obvious -- and the ones that aren't (ie relaxed)
> have the justification in the comments.

Ok, care to resend the whole thing?

Thanks,

	tglx


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