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Date: Wed, 18 Mar 2015 07:41:48 -0700
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: josh@joshtriplett.org, linux-kernel@vger.kernel.org,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Nicholas Miell <nmiell@comcast.net>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Ingo Molnar <mingo@redhat.com>, Alan Cox <gnomes@lxorguk.ukuu.org.uk>,
        Lai Jiangshan <laijs@cn.fujitsu.com>,
        Stephen Hemminger <stephen@networkplumber.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        David Howells <dhowells@redhat.com>
Subject: Re: [RFC PATCH v13] sys_membarrier(): system/process-wide memory
 barrier (x86)
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On Tue, Mar 17, 2015 at 07:27:15PM +0000, Mathieu Desnoyers wrote:
> ----- Original Message -----
> > ----- Original Message -----
> > > On Tue, Mar 17, 2015 at 01:22:02PM -0400, Mathieu Desnoyers wrote:
> > > > --- a/init/Kconfig
> > > > +++ b/init/Kconfig
> > > > @@ -1568,6 +1568,15 @@ config PCI_QUIRKS
> > > >  	  bugs/quirks. Disable this only if your target machine is
> > > >  	  unaffected by PCI quirks.
> > > >  
> > > > +config MEMBARRIER
> > > > +	bool "Enable membarrier() system call" if EXPERT
> > > > +	default y
> > > > +	help
> > > > +	  Enable the membarrier() system call that allows issuing
> > > > +	  memory barriers across cores.
> > > 
> > > Nit: CPUs, not cores.  Nothing here is specific to
> > > packages/cores/threads.
> > 
> > Fixed.
> > 
> > > 
> > > > --- a/kernel/rcu/update.c
> > > > +++ b/kernel/rcu/update.c
> > > > @@ -49,6 +49,8 @@
> > > >  #include <linux/module.h>
> > > >  #include <linux/kthread.h>
> > > >  #include <linux/tick.h>
> > > > +#include <linux/syscalls.h>
> > > > +#include <linux/membarrier.h>
> > > >  
> > > >  #define CREATE_TRACE_POINTS
> > > >  
> > > > @@ -775,3 +777,73 @@ late_initcall(rcu_verify_early_boot_tests);
> > > >  #else
> > > >  void rcu_early_boot_tests(void) {}
> > > >  #endif /* CONFIG_PROVE_RCU */
> > > > +
> > > > +#ifdef CONFIG_MEMBARRIER
> > > 
> > > As mentioned in my previous mail, please consider moving this to its own
> > > file, if it doesn't use any of the internals of kernel/rcu/update.c
> > > (which I don't think it does).  That then means you can enable/disable
> > > the entire file in the Makefile rather than using an #ifdef in the .c
> > > file.
> > 
> > Will do, thanks!
> 
> I'm adding include/uapi/linux/membarrier.h and kernel/membarrier.c,
> how should I add them to the MAINTAINERS file ?

I suggest adding them as their own entry, with yourself as maintainer.
I would be willing to be co-maintainer, and perhaps some of the others
in this thread would also be willing.

							Thanx, Paul