Date: Wed, 13 Jan 2010 14:17:27 -0500
From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
To: Nicholas Miell <nmiell@comcast.net>
Cc: paulmck@linux.vnet.ibm.com, linux-kernel@vger.kernel.org,
       Steven Rostedt <rostedt@goodmis.org>, Oleg Nesterov <oleg@redhat.com>,
       Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@elte.hu>,
       akpm@linux-foundation.org, josh@joshtriplett.org, tglx@linutronix.de,
       Valdis.Kletnieks@vt.edu, dhowells@redhat.com, laijs@cn.fujitsu.com,
       dipankar@in.ibm.com
Subject: Re: [RFC PATCH] introduce sys_membarrier(): process-wide memory
	barrier (v5)
Message-ID: <20100113191727.GA24742@Krystal>
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* Nicholas Miell (nmiell@comcast.net) wrote:
> On Wed, 2010-01-13 at 13:24 -0500, Mathieu Desnoyers wrote:
> > * Nicholas Miell (nmiell@comcast.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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