Date: Tue, 16 Mar 2004 12:14:56 -0500 From: John Baldwin <jhb@FreeBSD.org> To: Bosko Milekic <bmilekic@technokratis.com> Cc: freebsd-arch@freebsd.org Subject: Re: Read Copy Update Message-ID: <200403161214.31276.john@baldwin.cx> In-Reply-To: <20040316163359.GA7365@technokratis.com> References: <1077137806.28133.10.camel@herring.nlsystems.com> <200403161012.09174.john@baldwin.cx> <20040316163359.GA7365@technokratis.com>
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On Tuesday 16 March 2004 11:33 am, Bosko Milekic wrote: > On Tue, Mar 16, 2004 at 10:12:09AM -0500, John Baldwin wrote: > > > I was imagining a a pcpu flag which was a 'soft cli', i.e. if a cpu > > > fields an interrupt and the soft cli flag is set, it just clears the > > > interrupt flag in the trapframe and returns. It all works out the same > > > in the end. > > No because if you're in the middle of modifying a pcpu flag and you > take an interrupt you may get scheduled over to another CPU. You > would also have to temporarily pin down the thread to the current CPU > unless you do it with an in-thread flag. > > By the way, the point of all this is that with a combination of > soft-disables and short-term scheduler pinning we should be able to > take the common memory allocation case in UMA out of any lock > requirements (lockless in common case). > > > I have this partly implemented, but because the VM86 code really sucks > > (it just always enables interrupts) the invariants checks I have don't > > make it to single user mode. I haven't decided what to do about VM86 > > yet, and I also haven't handled the problem of switching away from > > interrupt context (for ithread preemption) and switching back and making > > that all work correctly w/o possibly dropping interrupts. > > Do you have your current changes in a separate p4 repo somewhere? The jhb_acpipci_crit branch. Like I said, though, it doesn't boot. There are lots of implementation notes in //depot/user/jhb/acpicpi_crit/notes. -- John Baldwin <john@baldwin.cx> <>< http://www.baldwin.cx/~john/ "Power Users Use the Power to Serve" = http://www.FreeBSD.org
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