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Re: Kernel Semaphores

To: "Kevin D. Kissell" <kevink@mips.com>
Subject: Re: Kernel Semaphores
From: Ralf Baechle <ralf@oss.sgi.com>
Date: Mon, 6 Dec 1999 19:13:51 -0200
Cc: Ralf Baechle <ralf@oss.sgi.com>, Linux SGI <linux@cthulhu.engr.sgi.com>
In-reply-to: <012901bf4029$2e465020$0ceca8c0@satanas.mips.com>
References: <012901bf4029$2e465020$0ceca8c0@satanas.mips.com>
Sender: owner-linuxmips@oss.sgi.com
On Mon, Dec 06, 1999 at 09:33:38PM +0100, Kevin D. Kissell wrote:

> >> To make it work on 32-bit CPUs, I looked at using
> >> the x386 model, but that one uses interrupt disables
> >> and is intrinsically SMP-unsafe.
> >
> >semaphore-helper.h uses spin_lock_irqsave which is smp-safe.  The way
> >we do things for 64-bit MIPS is just more performant.
> 
> spin_lock_irqsave() in 2.2.12 for MIPS is just a save_and_cli().
> The MIPS spin_lock macros all collapse the lock into nothingness.

Spinlocks are SMP safe; it's just the MIPS implementation which doesn't
get this right so far.

  Ralf

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