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From: Jamie Lokier <lk@tantalophile.demon.co.uk>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: "H. Peter Anvin" <hpa@zytor.com>, linux-kernel@vger.kernel.org
Subject: Re: furwocks: Fast Userspace Read/Write Locks
Date: Fri, 8 Mar 2002 19:32:57 +0000	[thread overview]
Message-ID: <20020308193257.B18247@kushida.apsleyroad.org> (raw)
In-Reply-To: <E16iwkE-000216-00@wagner.rustcorp.com.au> <20020307153228.3A6773FE06@smtp.linux.ibm.com> <20020307104241.D24040@devserv.devel.redhat.com> <20020307191043.9C5F33FE15@smtp.linux.ibm.com> <a68htg$bc1$1@cesium.transmeta.com> <20020308172706.1e4d3f5e.rusty@rustcorp.com.au>
In-Reply-To: <20020308172706.1e4d3f5e.rusty@rustcorp.com.au>; from rusty@rustcorp.com.au on Fri, Mar 08, 2002 at 05:27:06PM +1100

Rusty Russell wrote:
> One or more userspace processes share address space, so they can both do
> simple atomic operations on the same memory (hence the new PROT_SEM flag to
> mmap/mprotect for architectures which need to know).  They agree that "this
> address contains an integer which we use as a mutex" (aka. struct futex).

FWIW, there is a precedent from FreeBSD for a MAP_HASSEMAPHORE flag
meaning "this region may contain semaphores".

I don't know if that implies anything about the support of futex system
calls, but it may be the appropriate flag to indicate "atomic operations
are seen as such between processes on these pages".

-- Jamie

  parent reply	other threads:[~2002-03-08 19:33 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-03-07 12:11 Rusty Russell
2002-03-07 12:40 ` Peter Wächtler
2002-03-07 14:41   ` Hubertus Franke
2002-03-07 12:50 ` Arjan van de Ven
2002-03-07 15:33   ` Hubertus Franke
2002-03-07 15:42     ` Arjan van de Ven
2002-03-07 19:11       ` Hubertus Franke
2002-03-07 20:17         ` H. Peter Anvin
2002-03-08  6:27         ` Rusty Russell
2002-03-08  6:29           ` H. Peter Anvin
2002-03-08  7:09             ` Rusty Russell
2002-03-08 19:32           ` Jamie Lokier [this message]
2002-03-08  1:22     ` Rusty Russell
2002-03-08  3:26       ` H. Peter Anvin
2002-03-08  9:21       ` Peter Wächtler
2002-03-08 18:13         ` Hubertus Franke
2002-03-09  4:50         ` Rusty Russell
2002-03-11 18:47           ` Hubertus Franke
2002-03-07 15:28 ` Hubertus Franke

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