linux-kernel - Re: [PATCH 0/2] jump label: 2.6.38 updates

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Message-ID: <1297704447.5226.127.camel@laptop>
Date:	Mon, 14 Feb 2011 18:27:27 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Jason Baron <jbaron@...hat.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	hpa@...or.com, mingo@...e.hu, tglx@...utronix.de,
	andi@...stfloor.org, roland@...hat.com, rth@...hat.com,
	masami.hiramatsu.pt@...achi.com, fweisbec@...il.com,
	avi@...hat.com, davem@...emloft.net, sam@...nborg.org,
	ddaney@...iumnetworks.com, michael@...erman.id.au,
	linux-kernel@...r.kernel.org, Mike Frysinger <vapier@...too.org>,
	Chris Metcalf <cmetcalf@...era.com>,
	dhowells <dhowells@...hat.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	"heiko.carstens" <heiko.carstens@...ibm.com>,
	benh <benh@...nel.crashing.org>
Subject: Re: [PATCH 0/2] jump label: 2.6.38 updates

On Mon, 2011-02-14 at 12:18 -0500, Steven Rostedt wrote:

> mn10300:
> #define atomic_read(v)  ((v)->counter)

> tile:
> static inline int atomic_read(const atomic_t *v)
> {
>        return v->counter;
> }

Yeah, I already send email to the respective maintainers telling them
they might want to fix this ;-)


> So all but a few have basically (as you said on IRC)
> #define atomic_read(v) ACCESS_ONCE(v)

ACCESS_ONCE(v->counter), but yeah :-)

> Those few are blackfin, s390, powerpc and tile.
> 
> s390 probably doesn't need that much of a big hammer with atomic_read()
> (unless it uses it in its own arch that expects it to be such).

Right, it could just do the volatile thing..

> powerpc could probably be converted to just the volatile code as
> everything else. Not sure why it did it that way. To be different?

Maybe that code was written before we all got inventive with the
volatile cast stuff..

> blackfin, seems to be doing quite a lot. Not sure if it is required, but
> that may need a bit of investigating to understand why it does the
> raw_uncached thing.

>From what I can tell its flushing its write cache, invalidating its
d-cache and then issue the read, something which is _way_ overboard.

> Maybe we could move the atomic_read() out of atomic and make it a
> standard inline for all (in kernel.h)?

Certainly looks like that might work..

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