linux-kernel - Re: [PATCH v4 3/4] futex: Document ordering guarantees

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Message-ID: <1387487274.3510.18.camel@dvhart-mobl4.amr.corp.intel.com>
Date:	Thu, 19 Dec 2013 13:07:54 -0800
From:	Darren Hart <dvhart@...ux.intel.com>
To:	Davidlohr Bueso <davidlohr@...com>
Cc:	Randy Dunlap <rdunlap@...radead.org>, linux-kernel@...r.kernel.org,
	mingo@...hat.com, peterz@...radead.org, tglx@...utronix.de,
	paulmck@...ux.vnet.ibm.com, efault@....de, jeffm@...e.com,
	torvalds@...ux-foundation.org, jason.low2@...com,
	Waiman.Long@...com, tom.vaden@...com, scott.norton@...com,
	aswin@...com, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH v4 3/4] futex: Document ordering guarantees

On Thu, 2013-12-19 at 13:00 -0800, Davidlohr Bueso wrote:
> On Thu, 2013-12-19 at 12:51 -0800, Randy Dunlap wrote:
> > On 12/19/13 12:45, Davidlohr Bueso wrote:
> > > From: Thomas Gleixner <tglx@...utronix.de>
> > > 
> > > That's essential, if you want to hack on futexes.
> > > 
> > > Cc: Ingo Molnar <mingo@...nel.org>
> > > Cc: Darren Hart <dvhart@...ux.intel.com>
> > > Acked-by: Peter Zijlstra <peterz@...radead.org>
> > > Cc: Thomas Gleixner <tglx@...utronix.de>
> > > Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> > > Cc: Mike Galbraith <efault@....de>
> > > Cc: Jeff Mahoney <jeffm@...e.com>
> > > Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> > > Cc: Scott Norton <scott.norton@...com>
> > > Cc: Tom Vaden <tom.vaden@...com>
> > > Cc: Aswin Chandramouleeswaran <aswin@...com>
> > > Cc: Waiman Long <Waiman.Long@...com>
> > > Cc: Jason Low <jason.low2@...com>
> > > Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> > > Signed-off-by: Davidlohr Bueso <davidlohr@...com>
> > > ---
> > >  kernel/futex.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> > >  1 file changed, 57 insertions(+)
> > > 
> > > diff --git a/kernel/futex.c b/kernel/futex.c
> > > index 577481d..af1fc31 100644
> > > --- a/kernel/futex.c
> > > +++ b/kernel/futex.c
> > > @@ -69,6 +69,63 @@
> > >  
> > >  #include "locking/rtmutex_common.h"
> > >  
> > > +/*
> > > + * Basic futex operation and ordering guarantees:
> > > + *
> > > + * The waiter reads the futex value in user space and calls
> > > + * futex_wait(). It computes the hash bucket and acquires the hash
> > 
> > does                It
> > refer to "the waiter" or to futex_wait()?
> > I read it as referring to the waiter, but ISTM that the comments are using It
> > to refer to futex_wait()... ???
> > 
> 
> Yes, it refers to futex_wait(), which IMO in a futex context is pretty
> clear.


Agreed.


-- 
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel


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