From owner-freebsd-hackers  Mon Jul 19 14:17:31 1999
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Date: Tue, 20 Jul 1999 07:16:10 +1000
From: Peter Jeremy <jeremyp@gsmx07.alcatel.com.au>
Subject: Re: Determining the return address
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Cc: des@flood.ping.uio.no
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Dag-Erling Smorgrav <des@flood.ping.uio.no> wrote:
>Alfred Perlstein <bright@rush.net> writes:
>> specifically how you say you increment it, then decrement it,
>> if you have multiple handlers where one can interupt another
>> you can have the counter get jumbled.
>
>Not if increment / decrement is atomic.

Which it _isn't_ in general.  The only case where it _is_ atomic is on
a UP i386, where the compiler has generated an `inc' instruction
(which it might not).

Check out /sys/alpha/include/atomic.h or a recent (less than a week
old [1]) -current version of /sys/i386/include/atomic.h for atomic
code.

Peter

[1] It was broken prior to this.


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