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

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Date:	Sun, 22 Dec 2013 15:24:09 -0800
From:	Davidlohr Bueso <davidlohr@...com>
To:	Darren Hart <dvhart@...ux.intel.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 15:19 -0800, Darren Hart wrote:
> 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!

Absolutely.

I've found that we have the same grammatical error when describing
futex_wake() as well, so I've updated the doc to say "This function"
instead of "It".

Thanks,
Davidlohr

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