Date: Thu, 25 Nov 2010 10:28:49 -0500 From: John Baldwin <jhb@FreeBSD.org> To: Andriy Gapon <avg@freebsd.org> Cc: Garrett Cooper <yanegomi@gmail.com>, freebsd-hackers@freebsd.org Subject: Re: Best way to determine if an IRQ is present Message-ID: <4CEE80B1.6000602@FreeBSD.org> In-Reply-To: <4CEBDD42.5010007@freebsd.org> References: <AANLkTi=%2ByXVrcWDC1QZLA0JWNOQjWG%2Bud_BmwiMXAMXt@mail.gmail.com> <201011220924.53709.jhb@freebsd.org> <4CEBDD42.5010007@freebsd.org>
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Andriy Gapon wrote: > on 22/11/2010 16:24 John Baldwin said the following: >> Well, the real solution is actually larger than described in the PR. What you >> really want to do is take the logical CPUs offline when they are "halted". >> Taking a CPU offline should trigger an EVENTHANDLER that various bits of code >> could invoke. In the case of platforms that support binding interrupts to >> CPUs (x86 and sparc64 at least), they would install an event handler that >> searches the MD interrupt tables (e.g. the interrupt_sources[] array on x86) >> and move bound interrupts to other CPUs. However, I think all the interrupt >> bits will be MD, not MI. > > That's a good idea and a comprehensive approach. > One minor technical detail - should an offlined CPU be removed from all_cpus mask/set? That's tricky. In other e-mails I've had on this topic, the idea has been to have a new online_cpus mask and maybe a CPU_ONLINE() test macro similar to CPU_ABSENT(). In that case, an offline CPU should still be in all_cpus, but many places that use all_cpus would need to use online_cpus instead. -- John Baldwin
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