linux-kernel - Re: [tip:locking/core] futex: Enhance comments in futex_lock

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Date:	Mon, 20 Jul 2015 14:24:32 -0700
From:	Darren Hart <dvhart@...radead.org>
To:	hpa@...or.com, mingo@...nel.org, linux-kernel@...r.kernel.org,
	peterz@...radead.org, darren@...art.com, dave@...olabs.net,
	dbueso@...e.de, tglx@...utronix.de
Cc:	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:locking/core] futex: Enhance comments in futex_lock_pi()
 for blocking paths

On Mon, Jul 20, 2015 at 03:57:37AM -0700, tip-bot for Davidlohr Bueso wrote:
> Commit-ID:  767f509ca11269c2bcd92e3972a93096f2173ac0
> Gitweb:     http://git.kernel.org/tip/767f509ca11269c2bcd92e3972a93096f2173ac0
> Author:     Davidlohr Bueso <dave@...olabs.net>
> AuthorDate: Mon, 29 Jun 2015 23:26:01 -0700
> Committer:  Thomas Gleixner <tglx@...utronix.de>
> CommitDate: Mon, 20 Jul 2015 11:45:45 +0200
> 
> futex: Enhance comments in futex_lock_pi() for blocking paths
> 
> ... serves a bit better to clarify between blocking
> and non-blocking code paths.
> 
> Signed-off-by: Davidlohr Bueso <dbueso@...e.de>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Darren Hart <darren@...art.com>
> Cc: Davidlohr Bueso <dave@...olabs.net>
> Link: http://lkml.kernel.org/r/1435645562-975-2-git-send-email-dave@stgolabs.net
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>  kernel/futex.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/futex.c b/kernel/futex.c
> index c4a182f..153eb22 100644
> --- a/kernel/futex.c
> +++ b/kernel/futex.c
> @@ -2268,8 +2268,11 @@ static long futex_wait_restart(struct restart_block *restart)
>  /*
>   * Userspace tried a 0 -> TID atomic transition of the futex value
>   * and failed. The kernel side here does the whole locking operation:
> - * if there are waiters then it will block, it does PI, etc. (Due to
> - * races the kernel might see a 0 value of the futex too.)
> + * if there are waiters then it will block as a consequence of relying
> + * on rt-mutexes, it does PI, etc. (Due to races the kernel might see
> + * a 0 value of the futex too.).
> + *
> + * Also serves as futex trylock_pi()'ing, and due semantics.

Hrm, what does 'due' mean here?

-- 
Darren Hart
Intel Open Source Technology Center
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