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From: Hubertus Franke <frankeh@watson.ibm.com>
Reply-To: frankeh@watson.ibm.com
Organization: IBM Research
To: Rusty Russell <rusty@rustcorp.com.au>
Subject: Re: [PATCH] Fast Userspace Mutexes III.
Date: Tue, 5 Mar 2002 10:15:44 -0500
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On Monday 04 March 2002 11:48 pm, Rusty Russell wrote:
> On Mon, 4 Mar 2002 15:48:48 -0500
>
> Hubertus Franke <frankeh@watson.ibm.com> wrote:
> > Also, the check on PROT_SEM is missing. I tried this before and glibc
> > filtered these flags out when set. But effectively, one still needs to
> > check whether semaphores are allowed during the sys_futex call.
>
> Neither arch I care about (ppc, x86) needs to do anything with PROT_SEM, so
> it's OK.  glibc will have to be fixed on any architectures which require
> help here, and a hook will be needed somewhere in the kernel for them.
>
> I didn't implement it because I don't *know* which archs will need
> something, and what they will need.  Hence my request for arch maintainers
> to step forward (Linus said they exist, and I believe him).
>
> Hope that clarifies this particular wart...
> Rusty.

Clarifies only partially.

I agree to put it there if its not used as a means to define whether
user locks are permitted or not. If that is the intention, then the current 
futex will need to check every access through find_vma(), which we
both know nobody wants to do.

So it can only be used for architectural hints, agreed ?

-- 
-- Hubertus Franke  (frankeh@watson.ibm.com)
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