Date: Mon, 7 Jan 2002 16:24:54 -0500 (EST) From: Daniel Eischen <eischen@pcnet1.pcnet.com> To: Nate Williams <nate@yogotech.com> Cc: 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: <Pine.SUN.3.91.1020107161934.22099C-100000@pcnet1.pcnet.com> In-Reply-To: <15418.3903.102913.925450@caddis.yogotech.com>
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On Mon, 7 Jan 2002, Nate Williams wrote: > > > > 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.) 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/). -- Dan Eischen To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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