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Re: Compilers and RCU readers: Once more unto the breach!
- From: "Paul E. McKenney" <paulmck at linux dot vnet dot ibm dot com>
- To: Ingo Molnar <mingo at kernel dot org>
- Cc: Linus Torvalds <torvalds at linux-foundation dot org>, Will Deacon <will dot deacon at arm dot com>, Linux Kernel Mailing List <linux-kernel at vger dot kernel dot org>, "c++std-parallel at accu dot org" <c++std-parallel at accu dot org>, "linux-arch at vger dot kernel dot org" <linux-arch at vger dot kernel dot org>, "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>, p796231 <Peter dot Sewell at cl dot cam dot ac dot uk>, "mark dot batty at cl dot cam dot ac dot uk" <Mark dot Batty at cl dot cam dot ac dot uk>, Peter Zijlstra <peterz at infradead dot org>, Ramana Radhakrishnan <Ramana dot Radhakrishnan at arm dot com>, David Howells <dhowells at redhat dot com>, Andrew Morton <akpm at linux-foundation dot org>, "michaelw at ca dot ibm dot com" <michaelw at ca dot ibm dot com>
- Date: Fri, 22 May 2015 06:12:52 -0700
- Subject: Re: Compilers and RCU readers: Once more unto the breach!
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- Reply-to: paulmck at linux dot vnet dot ibm dot com
On Fri, May 22, 2015 at 08:43:44AM +0200, Ingo Molnar wrote:
> * Linus Torvalds <email@example.com> wrote:
> > (a) the "official" rules are completely pointless, and make sense
> > only because the standard is written for some random "abstract
> > machine" that doesn't actually exist.
> Presuming the intent of the abstract machine specification is to avoid
> being seen as biased towards any specific machine (politics), maybe
> write this as:
> (a) the "official" rules are written for a somewhat weird and
> complex "union of all known and theoretically possible CPU
> architectures that exist or which might exist in the future",
> which machine does not actually exist in practice, but which
> allows a single abstract set of rules to apply to all machines.
> These rules are complex, but if applied to a specific machine
> they become considerably simpler. Here's a few examples: ...
> (Assuming it's a goal of this standard to be human parseable to more
> than a few dozen people on the planet.)
Should something based on Section 7.9 go in, then I would need to add
a more developer-friendly explanation in Documentation/RCU, no two
ways about it! ;-)