linux-kernel - Re: [tip:perf/core] tools/perf: Add required memory barriers

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 6 Nov 2013 17:07:20 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Vince Weaver <vince@...ter.net>
Cc:	mingo@...nel.org, hpa@...or.com, anton@...ba.org,
	mathieu.desnoyers@...ymtl.ca, linux-kernel@...r.kernel.org,
	michael@...erman.id.au, paulmck@...ux.vnet.ibm.com,
	benh@...nel.crashing.org, fweisbec@...il.com, VICTORK@...ibm.com,
	tglx@...utronix.de, oleg@...hat.com, mikey@...ling.org,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:perf/core] tools/perf: Add required memory barriers

On Wed, Nov 06, 2013 at 03:44:56PM +0100, Peter Zijlstra wrote:
> long head = ((__atomic long)pc->data_head).load(memory_order_acquire);
> 
> coupled with:
> 
> ((__atomic long)pc->data_tail).store(tail, memory_order_release);
> 
> might be the 'right' and proper C11 incantations to avoid having to
> touch kernel macros; but would obviously require a recent compiler.
> 
> Barring that, I think we're stuck with:
> 
> long head = ACCESS_ONCE(pc->data_head);
> smp_rmb();
> 
> ...
> 
> smp_mb();
> pc->data_tail = tail;
> 
> And using the right asm goo for the barriers. That said, all these asm
> barriers should include a compiler barriers (memory clobber) which
> _should_ avoid the worst compiler trickery -- although I don't think it
> completely obviates the need for ACCESS_ONCE() -- uncertain there.

http://software.intel.com/en-us/articles/single-producer-single-consumer-queue/

There's one for icc on x86.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/