linux-kernel - RE: Control Dependencies vs C Compilers

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Message-ID: <0a0403a430b14484a026b52a5ecbbeeb@AcuMS.aculab.com>
Date:   Tue, 6 Oct 2020 15:07:41 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Peter Zijlstra' <peterz@...radead.org>
CC:     "linux-toolchains@...r.kernel.org" <linux-toolchains@...r.kernel.org>,
        Will Deacon <will@...nel.org>,
        Paul McKenney <paulmck@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stern@...land.harvard.edu" <stern@...land.harvard.edu>,
        "parri.andrea@...il.com" <parri.andrea@...il.com>,
        "boqun.feng@...il.com" <boqun.feng@...il.com>,
        "npiggin@...il.com" <npiggin@...il.com>,
        "dhowells@...hat.com" <dhowells@...hat.com>,
        "j.alglave@....ac.uk" <j.alglave@....ac.uk>,
        "luc.maranget@...ia.fr" <luc.maranget@...ia.fr>,
        "akiyks@...il.com" <akiyks@...il.com>,
        "dlustig@...dia.com" <dlustig@...dia.com>,
        "joel@...lfernandes.org" <joel@...lfernandes.org>,
        "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>
Subject: RE: Control Dependencies vs C Compilers

> Please go read memory-barriers.txt for a bunch of other examples.

My brain hurts.
It's not as though I've not known about most of this since
the first SMP capable SPARC cpus that had a 'store buffer'.
(Probably 30 years ago.)

I sometimes wonder whether compiling things like the kernel
requires a compiler mode that defaults everything (except
function locals) to 'volatile'.
Although that still does fix control dependencies.

	David

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