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Date: Thu, 07 Mar 2002 13:40:49 +0100
From: Peter =?ISO-8859-1?Q?W=E4chtler?= <pwaechtler@loewe-komp.de>
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To: Rusty Russell <rusty@rustcorp.com.au>
CC: linux-kernel@vger.kernel.org, Hubertus Franke <frankeh@watson.ibm.com>,
        lse-tech@lists.sourceforge.net
Subject: Re: furwocks: Fast Userspace Read/Write Locks
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Rusty Russell wrote:

> This is a userspace implementation of rwlocks on top of futexes.
> 

With the futex approach in mind: Does anybody think it's desirable to have

pthread_cond_wait/signal and pthread_mutex_* with inter process scope build
into the kernel as system call?

The only issue I see so far, is that libpthread should get a "reserved" namespace
entry ( /dev/shm/.linuxthreads-locks ?) to hold all the PTHREAD_PROCESS_SHARE
locks/condvars.

OTOH Irix seems to implement inter process locks as syscall, so that the kernel does
all the bookkeeping. That approach denies a malicious program to trash all locks
in the system...

Hmh, then we could implement a per user /dev/shm/.linuxthreads-lock-<uid> with
tight permissions?

What do you think?

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