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Date: Mon, 5 Aug 2002 23:35:42 +0200
From: Andi Kleen <ak@suse.de>
To: Jamie Lokier <lk@tantalophile.demon.co.uk>
Cc: Andi Kleen <ak@suse.de>, Linus Torvalds <torvalds@transmeta.com>,
       linux-kernel@vger.kernel.org
Subject: Re: context switch vs. signal delivery [was: Re: Accelerating user  mode linux]
Message-ID: <20020805233542.A12753@wotan.suse.de>
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On Mon, Aug 05, 2002 at 10:30:06PM +0100, Jamie Lokier wrote:
> Andi Kleen wrote:
> > +	err |= setup_sigcontext(&frame->sc, &frame->fpstate, regs, set->sig[0], 
> > +				(ka->sa.sa_flags&SA_NOFP));
> 
> >  	err |= setup_sigcontext(&frame->uc.uc_mcontext, &frame->fpstate,
> > -			        regs, set->sig[0]);
> > +			        regs, set->sig[0], !!(ka->sa.sa_flags&SA_NOFP));
> 
> 1: Why the inconsistency between the two ways the SA_NOFP flag is checked?

I don't remember. Probably there was some reason in an earlier version
of the code. The !! could be probably removed now.

> 
> 2: What happens when the user's signal handler decides it wants to save
> the FPU state itself (after all) and proceed with some FPU use.  Will
> sigreturn restore the user-saved FPU state?  Just curious.

Nope it won't because there is no saved state. The previous context's FPU 
state will be silently corrupted.

-Andi
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