linux-kernel - Re: [RFC PATCH] introduce sys_membarrier(): process-wide memory barrier (v5)

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Message-ID: <20100113191727.GA24742@Krystal>
Date:	Wed, 13 Jan 2010 14:17:27 -0500
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Nicholas Miell <nmiell@...cast.net>
Cc:	paulmck@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	Steven Rostedt <rostedt@...dmis.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>, akpm@...ux-foundation.org,
	josh@...htriplett.org, tglx@...utronix.de, Valdis.Kletnieks@...edu,
	dhowells@...hat.com, laijs@...fujitsu.com, dipankar@...ibm.com
Subject: Re: [RFC PATCH] introduce sys_membarrier(): process-wide memory
	barrier (v5)

* Nicholas Miell (nmiell@...cast.net) wrote:
> On Wed, 2010-01-13 at 13:24 -0500, Mathieu Desnoyers wrote:
> > * Nicholas Miell (nmiell@...cast.net) wrote:
> > 
> > > The whole point of compat and incompat flags is that it allows new
> > > applications to run on old kernels and either work or fail as
> > > appropriate, depending on whether the new features they're using must be
> > > implemented or can be silently ignored.
> > 
> > I see. Thanks for the explanation. Then the expedited flag should
> > clearly be part of the mandatory flags.
> > 
> > Can you point me to other system calls that are doing this ?
> > 
> > Thanks,
> > 
> > Mathieu
> 
> Not off the top of my head, but I did steal the idea from the ext2/3/4
> disk format.

Sounds a bit over-engineered to me for system calls, but who knows if we
eventually have to extend sys_membarrier(). This involves that, right
now, I'd have to add a header to include/linux to define these flags.
Also, "int expedited" is a bit clearer, but less flexible, than "int
flags". Anyone else have comments about this ?

Thanks,

Mathieu

-- 
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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