From: Darren Hart <dvhart@linux.intel.com>
To: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>
Cc: "Carlos O'Donell" <carlos@redhat.com>,
Ingo Molnar <mingo@elte.hu>, Jakub Jelinek <jakub@redhat.com>,
"linux-man@vger.kernel.org" <linux-man@vger.kernel.org>,
lkml <linux-kernel@vger.kernel.org>,
Davidlohr Bueso <davidlohr.bueso@hp.com>,
Arnd Bergmann <arnd@arndb.de>,
Steven Rostedt <rostedt@goodmis.org>,
Peter Zijlstra <peterz@infradead.org>,
Linux API <linux-api@vger.kernel.org>,
Torvald Riegel <triegel@redhat.com>,
Roland McGrath <roland@redhat.com>,
Darren Hart <dvhart@infradead.org>,
Anton Blanchard <anton@samba.org>, Petr Baudis <pasky@suse.cz>,
Eric Dumazet <edumazet@google.com>,
bill o gallmeister <bgallmeister@gmail.com>,
Jan Kiszka <jan.kiszka@siemens.com>,
Daniel Wagner <wagi@monom.org>, Rich Felker <dalias@libc.org>
Subject: Re: futex(2) man page update help request
Date: Fri, 16 Jan 2015 16:46:39 -0800 [thread overview]
Message-ID: <D0DEECA2.B7EAD%dvhart@linux.intel.com> (raw)
In-Reply-To: <54B97A72.2050205@gmail.com>
On 1/16/15, 12:54 PM, "Michael Kerrisk (man-pages)"
<mtk.manpages@gmail.com> wrote:
>On 01/16/2015 04:20 PM, Thomas Gleixner wrote:
>> On Fri, 16 Jan 2015, Michael Kerrisk (man-pages) wrote:
>>
>>> Hello Thomas,
>>>
>>> On 01/15/2015 11:23 PM, Thomas Gleixner wrote:
>>>> On Thu, 15 Jan 2015, Michael Kerrisk (man-pages) wrote:
>>>>>> [EINVAL] uaddr equal uaddr2. Requeue to same futex.
>>>>>
>>>>> ??? I added this, but does this error not occur only for PI requeues?
>>>>
>>>> It's equally wrong for normal futexes. And its actually the same code
>>>> checking for this for all variants.
>>>
>>> I don't understand "equally wrong" in your reply, I'm sorry. Do you
>>> mean:
>>>
>>> a) This error text should be there for both normal and PI requeues
>>
>> It is there for both. The requeue code has that check independent of
>> the requeue type (normal/pi). It never makes sense to requeue
>> something to itself whether normal or pi futex. We added this for PI,
>> because there it is harmful, but we did not special case it. So normal
>> futexes get the same treatment.
>
>Hello Thomas,
>
>Color me stupid, but I can't see this in futex_requeue(). Where is that
>check that is "independent of the requeue type (normal/pi)"?
>
>When I look through futex_requeue(), all the likely looking sources
>of EINVAL are governed by a check on the 'requeue_pi' argument.
Right, in the non-PI case, I believe there are valid use cases: move to
the back of the FIFO, for example (OK, maybe the only example?). Both
tests ensuring uaddr1 != uaddr2 are under the requeue_pi conditional
block. The second compares the keys in case they are not FUTEX_PRIVATE
(uaddrs would be different, but still the same backing store).
Thomas, am I missing a test for this someplace else?
--
Darren Hart
Intel Open Source Technology Center
next prev parent reply other threads:[~2015-01-17 0:46 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-14 10:35 futex(2) man page update help request Michael Kerrisk (man-pages)
2014-05-14 16:18 ` Darren Hart
2014-05-14 19:03 ` Michael Kerrisk (man-pages)
2014-05-14 19:59 ` Darren Hart
2014-05-14 20:23 ` Carlos O'Donell
2014-05-14 20:44 ` Andy Lutomirski
2014-05-14 23:34 ` Thomas Gleixner
2014-05-15 3:12 ` Carlos O'Donell
2014-05-15 4:49 ` Michael Kerrisk (man-pages)
2014-05-15 4:53 ` Michael Kerrisk (man-pages)
2014-05-15 14:14 ` Thomas Gleixner
2014-05-15 20:19 ` Michael Kerrisk (man-pages)
2014-08-04 14:46 ` Carlos O'Donell
2014-05-15 20:35 ` Darren Hart
2015-01-15 15:12 ` Michael Kerrisk (man-pages)
2015-01-17 1:33 ` Darren Hart
2015-01-17 9:16 ` Michael Kerrisk (man-pages)
2015-01-17 19:26 ` Darren Hart
2015-01-18 10:18 ` Michael Kerrisk (man-pages)
2015-01-15 15:10 ` Michael Kerrisk (man-pages)
2015-01-15 22:23 ` Thomas Gleixner
2015-01-16 15:17 ` Michael Kerrisk (man-pages)
2015-01-16 15:20 ` Thomas Gleixner
2015-01-16 20:54 ` Michael Kerrisk (man-pages)
2015-01-17 0:46 ` Darren Hart [this message]
2015-01-19 10:45 ` Thomas Gleixner
2015-01-19 14:07 ` Michael Kerrisk (man-pages)
2015-01-23 18:19 ` Torvald Riegel
2015-01-24 10:05 ` Thomas Gleixner
2015-01-24 12:58 ` Torvald Riegel
2015-01-24 16:25 ` Thomas Gleixner
2015-01-17 0:56 ` Davidlohr Bueso
2015-01-17 1:11 ` Darren Hart
2015-01-23 18:29 ` Torvald Riegel
2015-01-24 11:35 ` Thomas Gleixner
2015-01-24 13:12 ` Torvald Riegel
2015-01-27 7:48 ` Michael Kerrisk (man-pages)
2015-02-05 19:57 ` Darren Hart
2014-05-15 8:13 ` Peter Zijlstra
2014-05-15 15:43 ` Darren Hart
2014-05-15 8:14 ` Peter Zijlstra
2014-05-15 13:18 ` Carlos O'Donell
2014-05-15 13:22 ` Peter Zijlstra
2014-05-15 13:49 ` Michael Kerrisk (man-pages)
2014-05-15 13:55 ` Peter Zijlstra
2014-05-15 14:39 ` Carlos O'Donell
2014-05-15 15:11 ` Peter Zijlstra
2014-05-14 20:56 ` Davidlohr Bueso
2014-05-14 21:03 ` Darren Hart
2014-05-14 22:21 ` Paul E. McKenney
2014-05-15 0:28 ` H. Peter Anvin
2014-05-15 0:35 ` Andy Lutomirski
2014-05-15 0:41 ` H. Peter Anvin
2014-05-15 19:10 ` Carlos O'Donell
2014-05-14 21:05 ` Davidlohr Bueso
2014-05-15 15:15 ` Joseph S. Myers
2014-05-15 0:18 ` H. Peter Anvin
2014-05-15 5:21 ` Darren Hart
2014-05-15 8:23 ` Peter Zijlstra
2014-05-15 13:46 ` Michael Kerrisk (man-pages)
2014-05-15 14:59 ` H. Peter Anvin
2014-05-15 15:42 ` chrubis
2014-05-15 15:52 ` H. Peter Anvin
2014-05-15 16:01 ` chrubis
2014-05-15 16:07 ` H. Peter Anvin
2014-05-15 16:17 ` chrubis
2014-05-15 16:56 ` H. Peter Anvin
2014-05-15 17:06 ` chrubis
2014-05-15 15:47 ` Darren Hart
2014-05-15 15:35 ` chrubis
2014-05-15 15:28 ` chrubis
2014-05-15 15:40 ` Steven Rostedt
2014-05-15 16:14 ` Darren Hart
2014-05-15 16:30 ` chrubis
2014-05-15 18:17 ` Darren Hart
2014-05-15 19:05 ` chrubis
2014-05-15 19:38 ` Darren Hart
2014-08-11 10:19 ` chrubis
2014-11-26 13:41 ` Cyril Hrubis
2015-02-16 13:14 ` Cyril Hrubis
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