linux-kernel - Re: Memory synchronization vs. interrupt handlers

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Message-ID: <Pine.LNX.4.44L0.1308291017070.1170-100000@iolanthe.rowland.org>
Date:	Thu, 29 Aug 2013 10:19:03 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"H. Peter Anvin" <hpa@...or.com>
cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Russell King <linux@....linux.org.uk>,
	Ingo Molnar <mingo@...hat.com>,
	David Howells <dhowells@...hat.com>,
	Ming Lei <ming.lei@...onical.com>,
	USB list <linux-usb@...r.kernel.org>,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: Memory synchronization vs. interrupt handlers

On Wed, 28 Aug 2013, H. Peter Anvin wrote:

> On 08/28/2013 12:16 PM, Alan Stern wrote:
> > Russell, Peter, and Ingo:
> > 
> > Can you folks enlighten us regarding this issue for some common 
> > architectures?
> > 
> 
> On x86, IRET is a serializing instruction; it guarantees hard
> serialization of absolutely everything.

That answers half of the question.  What about the other half?  Does 
the CPU automatically serialize everything when it takes an interrupt?

> I would expect architectures that have weak memory ordering to put
> appropriate barriers in the IRQ entry/exit code.

Then would it be acceptable to mention this in the memory-barriers.txt 
file?

Alan Stern

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