Date: Thu, 15 Mar 2001 19:06:11 -0800 (PST) From: John Baldwin <jhb@FreeBSD.org> To: Matthew Jacob <mjacob@feral.com> Cc: arch@FreeBSD.org, Matt Dillon <dillon@earth.backplane.com> Subject: Re: Proposal for the CPU interrupt API Message-ID: <XFMail.010315190611.jhb@FreeBSD.org> In-Reply-To: <Pine.BSF.4.21.0103151842370.75234-100000@beppo.feral.com>
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On 16-Mar-01 Matthew Jacob wrote: > > >> >> :I would hope it would actually disable interrupts. >> >> On all cpu's or just the current cpu? > > Undefined. This depends on the architecture. Some architectures don't have a > global interrupt lockout mechanism. Some architectures vary as to whether or > not interrupts can be directed to one CPU, broadcast to all, or only for a > specific CPU. > > I think it's safe to say that given your specific platform's interrupt > mechanism, this disable_intr disables for this CPU only, or for all. Yep. I think that on the Alpha the IPL may be shared among all CPU's or may be per-CPU but I'm not sure. On the x86 it would only be for the local CPU, but all that any calling code should depend on is that it disables interrupts for the current CPU. > This function should probably only be called from MD code. It's not very MI. > The MI code has spin && adaptive locks and should be using just those. I > can't > imagine any case with the exception of debuggers and console I/O that might > get terribly upset about this- in which case these subsystems have extensions > into MD layers anyway. Yep. The primary offenders right now are the internals of the mutex code for spin locks (which disable interrupts to prevent preemption while holding a spinlock), some MD code for dealing with floating point state and various drivers living under sys/i386/isa/. Note that on the alpha, we used the CPU mask to implement spl()'s, so intr_disable() is (and has been) functionally equivalent to splhigh(), while on x86 they were two different things. > -matt -- John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/ PGP Key: http://www.baldwin.cx/~john/pgpkey.asc "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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