Date: Mon, 7 Jan 2002 14:52:20 -0700 From: Nate Williams <nate@yogotech.com> To: jb@Freebsd.org Cc: Nate Williams <nate@yogotech.com>, Dan Eischen <eischen@vigrid.com>, arch@Freebsd.org Subject: Re: Request for review: getcontext, setcontext, etc Message-ID: <15418.6292.572229.497144@caddis.yogotech.com> In-Reply-To: <Pine.SUN.3.91.1020107163310.29377A-100000@pcnet1.pcnet.com> References: <15418.4935.657413.312252@caddis.yogotech.com> <Pine.SUN.3.91.1020107163310.29377A-100000@pcnet1.pcnet.com>
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> On Mon, 7 Jan 2002, Nate Williams wrote: > > > Search for FP_SAVE_UC and FP_RESTORE_UC. You should find it in > > > pthread_private.h (where it is defined) and referenced in > > > uthread_kern.c and uthread_sig.c (src/lib/libc_r/uthread/). > > > > Found it. However, I could find the definition for mc_fpregs. > > See src/sys/sys/ucontext.h and src/sys/i386/include/ucontext.h. > > > Also, forgive my ignorance, but why are we using fnsave instead of > > fsave? From my reading of the x86 manuals, it would seem that there is > > the possibility of getting bogus FPU results with fnsave (vs. fsave) > > since by using fsave, we give the FPU a chance to finish up the current > > FPU operations before we save the state? I could see where they might > > be a race where we might end up storing intermediate results of the FPU > > in some instances. > > > > Or, is there something else I'm missing? (The reason I ask is that the > > JDK uses fsave to be 'safe', but maybe it's not buying us anything other > > than warm fuzzies. :) > > I don't know :-) That's what it was using when John Birrell was > maintaining libc_r. I can always change it... How about it John? Why is the thread code using 'fnsave' vs. 'fsave'? Are they any gotchas from it? Nate To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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