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To: Bruce Evans <bde@zeta.org.au>
cc: davidg@Root.COM, phk@freefall.freebsd.org,
        CVS-committers@freefall.freebsd.org, cvs-all@freefall.freebsd.org,
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Subject: Re: cvs commit: src/sys/i386/i386 swtch.s vm_machdep.c src/sys/i386/include pcb.h src/sys/i386/isa wd.c 
In-reply-to: Your message of "Fri, 19 Apr 1996 17:34:09 +1000."
             <199604190734.RAA06655@godzilla.zeta.org.au> 
Date: Fri, 19 Apr 1996 08:15:01 +0000
Message-ID: <29592.829901701@critter.tfs.com>
From: Poul-Henning Kamp <phk@critter.tfs.com>
Sender: owner-cvs-sys@FreeBSD.ORG
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> >>  Fix a bogon.  cpu_fork & savectx ecpected cpu_switch to restore %eax,
> >>  they shouldn't.
> 
> >   Oh? Why shouldn't they? The code as it was written looks correct to me (I
> >wrote it, so this shouldn't be too surprising :-)).
> 
> savectx() returned via cpu_switch() for the child case of cpu_fork(), so
> cpu_switch was expected to return both void and int :-).  It actually
> returned void, and the PCB_EAX initialization for the child case was
> never used.  I think the correct fix is to always return 1 or PCB_EAX(%edx)
> in cpu_switch().

That is a pointless waste of time, since cpu_switch cannot "fail" there
is no "return value" from it, so saving and reloading %eax is a waste of
time.


--
Poul-Henning Kamp           | phk@FreeBSD.ORG       FreeBSD Core-team.
http://www.freebsd.org/~phk | phk@login.dknet.dk    Private mailbox.
whois: [PHK]                | phk@ref.tfs.com       TRW Financial Systems, Inc.
Future will arrive by its own means, progress not so.