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Date: Wed, 25 Sep 2002 12:07:25 +0400
From: Oleg Drokin <green@namesys.com>
To: "David S. Miller" <davem@redhat.com>
Cc: zaitcev@redhat.com, mingo@redhat.com, linux-kernel@vger.kernel.org
Subject: Re: cmpxchg in 2.5.38
Message-ID: <20020925120725.A23559@namesys.com>
References: <20020925010044.A4464@devserv.devel.redhat.com> <20020925111820.A23225@namesys.com> <20020925.004719.61852840.davem@redhat.com>
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Hello!

On Wed, Sep 25, 2002 at 12:47:19AM -0700, David S. Miller wrote:

>    Ingo said that arches that cannot do cmpxchg in hardware should
>    provide spinlock-based version.
> That doesn't make any sense.

Yes, I know.

> If cmpxchg cannot work with user bits of memory, like
> cmpxchg is supposed to, it's really a crutch more than
> anything else.

Ingo's argument was that since there is only one place in code that accesses
that variable (map->page), it is safe to rely on such a crippled
cmpxchg implementation.

To not retell you whole story and avoid the role of broken phone,
here's info on prevous discussion on this topic:
Subject: Re: [patch] generic-pidhash-2.5.36-D4, BK-curr
September 20, From Ingo Molnar <mingo@elte.hu>, Message-ID: <Pine.LNX.4.44.0209201139290.1261-100000@localhost.localdomain>
September 20, From Ingo Molnar <mingo@elte.hu>, Message-ID: <Pine.LNX.4.44.0209201828090.8547-100000@localhost.localdomain>

Bye,
    Oleg