Re: [PATCH 6/6] ipc/sem.c: make semctl(,,{GETNCNT,GETZCNT}) standard compliant

[Manfred Spraul]

Hi Andrew,

On 05/20/2014 12:46 AM, Andrew Morton wrote:
> On Sun, 18 May 2014 09:58:37 +0200 Manfred Spraul <manfred@xxxxxxxxxxxxxxxx> 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.

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

--
    Manfred
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