Date: Thu, 25 Nov 2010 17:31:56 +0200 From: Andriy Gapon <avg@freebsd.org> To: John Baldwin <jhb@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: <4CEE816C.4060306@freebsd.org> In-Reply-To: <4CEE80B1.6000602@FreeBSD.org> References: <AANLkTi=%2ByXVrcWDC1QZLA0JWNOQjWG%2Bud_BmwiMXAMXt@mail.gmail.com> <201011220924.53709.jhb@freebsd.org> <4CEBDD42.5010007@freebsd.org> <4CEE80B1.6000602@FreeBSD.org>
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on 25/11/2010 17:28 John Baldwin said the following: > 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. > This sounds like a plan. CPU_FOREACH_ONLINE() could also come handy, Thanks! -- Andriy Gapon
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