linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Andrew Morton <akpm@linux-foundation.org>
To: Manfred Spraul <manfred@colorfullife.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Davidlohr Bueso <davidlohr.bueso@hp.com>,
	Michael Kerrisk <mtk.manpages@gmail.com>,
	1vier1@web.de
Subject: Re: [PATCH 6/6] ipc/sem.c: make semctl(,,{GETNCNT,GETZCNT}) standard compliant
Date: Tue, 20 May 2014 12:01:51 -0700	[thread overview]
Message-ID: <20140520120151.3cc813026fc73fbeb85ba1dc@linux-foundation.org> (raw)
In-Reply-To: <537B9F2D.6060606@colorfullife.com>

On Tue, 20 May 2014 20:30:05 +0200 Manfred Spraul <manfred@colorfullife.com> wrote:

> Hi Andrew,
> 
> On 05/20/2014 12:46 AM, Andrew Morton wrote:
> > On Sun, 18 May 2014 09:58:37 +0200 Manfred Spraul <manfred@colorfullife.com> wrote:
> >
> >> SUSv4 clearly defines how semncnt and semzcnt must be calculated:
> >> A task waits on exactly one semaphore:
> >> The semaphore from the first operation in the sop array that cannot proceed.
> >>
> >> The Linux implementation never followed the standard, it tried to count all
> >> semaphores that might be the reason why a task sleeps.
> >>
> >> This patch fixes that.
> > What are the back-compatibility implications of this change?
> A really good question:
> - there is no application in Fedora that uses GETNCNT or GETZCNT.
> - application that use only single-sop semop() are also safe, the 
> difference only affects complex apps.
> - portable application are also safe, the new behavior is standard 
> compliant.
> 
> But that's it. The old behavior existed in Linux from 0.99.something 
> until now.

OK, thanks - I slurped your thoughts and Michael's into the changelog
for posterity.

> What about adding a WARN_ON_ONCE() if the case where the behavior 
> differs happens?
> Should I write a patch?

That sounds prudent.

  reply	other threads:[~2014-05-20 19:01 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-05-18  7:58 [PATCH 0/6] ipc/sem.c: Fix semctl(,,{GETNCNT,GETZCNT}) Manfred Spraul
2014-05-18  7:58 ` [PATCH 1/6] ipc/sem.c: further whitespace cleanups Manfred Spraul
2014-05-18  7:58   ` [PATCH 2/6] ipc/sem.c: Bugfix for semctl(,,GETZCNT) Manfred Spraul
2014-05-18  7:58     ` [PATCH 3/6] ipc/sem.c: remove code duplication Manfred Spraul
2014-05-18  7:58       ` [PATCH 4/6] ipc/sem.c: Change perform_atomic_semop parameters Manfred Spraul
2014-05-18  7:58         ` [PATCH 5/6] ipc/sem.c: Store which operation blocks in perform_atomic_semop() Manfred Spraul
2014-05-18  7:58           ` [PATCH 6/6] ipc/sem.c: make semctl(,,{GETNCNT,GETZCNT}) standard compliant Manfred Spraul
2014-05-19 22:46             ` Andrew Morton
2014-05-20  6:56               ` Michael Kerrisk (man-pages)
2014-05-20 18:30               ` Manfred Spraul
2014-05-20 19:01                 ` Andrew Morton [this message]
2014-05-18 18:03 ` [PATCH 0/6] ipc/sem.c: Fix semctl(,,{GETNCNT,GETZCNT}) Davidlohr Bueso
  -- strict thread matches above, loose matches on Subject: below --
2014-05-10 10:03 Manfred Spraul
2014-05-10 10:03 ` [PATCH 1/6] ipc/sem.c: further whitespace cleanups Manfred Spraul
2014-05-10 10:03   ` [PATCH 2/6] ipc/sem.c: Bugfix for semctl(,,GETZCNT) Manfred Spraul
2014-05-10 10:03     ` [PATCH 3/6] ipc/sem.c: remove code duplication Manfred Spraul
2014-05-10 10:03       ` [PATCH 4/6] ipc/sem.c: Change perform_atomic_semop parameters Manfred Spraul
2014-05-10 10:03         ` [PATCH 5/6] ipc/sem.c: Store which operation blocks in perform_atomic_semop() Manfred Spraul
2014-05-10 10:03           ` [PATCH 6/6] ipc/sem.c: make semctl(,,{GETNCNT,GETZCNT}) standard compliant Manfred Spraul
2014-05-14 14:52             ` Davidlohr Bueso
2014-05-14 22:30               ` Andrew Morton
2014-05-15  4:24                 ` Manfred Spraul

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20140520120151.3cc813026fc73fbeb85ba1dc@linux-foundation.org \
    --to=akpm@linux-foundation.org \
    --cc=1vier1@web.de \
    --cc=davidlohr.bueso@hp.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=manfred@colorfullife.com \
    --cc=mtk.manpages@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).