Re: context switch vs. signal delivery [was: Re: Accelerating user mode linux]

From: Jamie Lokier (
Date: Mon Aug 05 2002 - 16:30:06 EST

A couple of questions.

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?

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.

-- Jamie
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