Date: Mon, 7 Jan 2002 14:12:31 -0700 From: Nate Williams <nate@yogotech.com> To: Daniel Eischen <eischen@pcnet1.pcnet.com> Cc: Nate Williams <nate@yogotech.com>, Dan Eischen <eischen@vigrid.com>, Peter Wemm <peter@wemm.org>, Archie Cobbs <archie@dellroad.org>, Alfred Perlstein <bright@mu.org>, arch@FreeBSD.ORG Subject: Re: Request for review: getcontext, setcontext, etc Message-ID: <15418.3903.102913.925450@caddis.yogotech.com> In-Reply-To: <Pine.SUN.3.91.1020107155415.22099A-100000@pcnet1.pcnet.com> References: <15418.2505.568006.160724@caddis.yogotech.com> <Pine.SUN.3.91.1020107155415.22099A-100000@pcnet1.pcnet.com>
next in thread | previous in thread | raw e-mail | index | archive | help
> > > What guarantees do you have that the FP state is restored > > > to where it was prior to calling foo_fp_munch_lots_more()? > > > > Because the code (and code similar to it) is called by the thread > > scheduler when a thread switches context. > > > > Above, if the thread switches context (involuntarily or voluntarily), > > the code I posted (and others routines similar to it it) also saves the > > context, and just before the context is switched back to the above > > thread, the FPU context is restored (along with all of the other > > information necessary to restore the thread context). > > > > Not all thread switches are done using yield. > > I am only concerned with voluntary switches; forget about signals > and preemptions. The threads library knows the difference between > voluntary and involuntary switches. Involuntary switches always > come from the kernel (in libc_r via signals) The JDK is the same. > and have the full FPU state saved (and restored when resumed). Is this done with fsave and frstor, which saves the entire context? Where is this done in the libc_r code? (I looked on my 4.5-PRE box, but nothing jumped out at me in grep search.) > Assume that setcontext > can tell if the FP state is saved or not and will restore it when > needed. Wonderful. > Assume that the kernel (or the threads library) will save > the FP state when a signal occurs. Wonderful. Nate To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?15418.3903.102913.925450>