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

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Message-ID: <1387495199.3510.38.camel@dvhart-mobl4.amr.corp.intel.com>
Date:	Thu, 19 Dec 2013 15:19:59 -0800
From:	Darren Hart <dvhart@...ux.intel.com>
To:	Randy Dunlap <rdunlap@...radead.org>
Cc:	Davidlohr Bueso <davidlohr@...com>, 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 15:05 -0800, Randy Dunlap wrote:
> On 12/19/13 13:07, Darren Hart wrote:
> > 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.
> > 
> > 
> 
> I'll just have to get by with disagreeing with both of you then.
> I say that the pronoun's antecedent is ambiguous (unclear).
> 

You are correct from a purely grammatical perspective, no argument
there. I just feel that the comment is clear enough from the context -
although perhaps people that hack on futexes should be excluded from
having an opinion here as we are biased :-)

If Davidlohr is going to resubmit for other reasons, then by all means,
please correct this per Randy's suggestion - I just didn't want to put
him (Davidlohr ;-) through another round of patches for this alone.

Thanks for ensuring our docs are as clear as possible Randy!

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


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