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Re: x86_64 Question: Are concurrent IPI requests safe?

From Thomas Gleixner <tglx@linutronix.de>
Newsgroups linux.kernel
Subject Re: x86_64 Question: Are concurrent IPI requests safe?
Date 2016-05-09 19:00 +0200
Message-ID <rwWHh-16Q-37@gated-at.bofh.it> (permalink)
References <rvLEe-3qs-5@gated-at.bofh.it> <rwUP8-7Fi-5@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Mon, 9 May 2016, Tetsuo Handa wrote:
> 
> It seems to me that APIC_BASE APIC_ICR APIC_ICR_BUSY are all constant
> regardless of calling cpu. Thus, native_apic_mem_read() and
> native_apic_mem_write() are using globally shared constant memory
> address and __xapic_wait_icr_idle() is making decision based on
> globally shared constant memory address. Am I right?

No. The APIC address space is per cpu. It's the same address but it's always
accessing the local APIC of the cpu on which it is called.

Thanks,

	tglx

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[next-20160506 mm,smp] hang up at csd_lock_wait() from drain_all_pages() Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-05-06 13:00 +0200
  x86_64 Question: Are concurrent IPI requests safe? Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-05-09 17:00 +0200
    Re: x86_64 Question: Are concurrent IPI requests safe? Thomas Gleixner <tglx@linutronix.de> - 2016-05-09 19:00 +0200
      Re: x86_64 Question: Are concurrent IPI requests safe? Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-05-11 15:30 +0200
        Re: x86_64 Question: Are concurrent IPI requests safe? Peter Zijlstra <peterz@infradead.org> - 2016-05-11 15:40 +0200
          Re: x86_64 Question: Are concurrent IPI requests safe? Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-05-11 16:10 +0200
            Re: x86_64 Question: Are concurrent IPI requests safe? Thomas Gleixner <tglx@linutronix.de> - 2016-05-11 16:40 +0200
              Re: x86_64 Question: Are concurrent IPI requests safe? Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-05-11 17:20 +0200
                Re: x86_64 Question: Are concurrent IPI requests safe? Peter Zijlstra <peterz@infradead.org> - 2016-05-11 19:50 +0200
                Re: x86_64 Question: Are concurrent IPI requests safe? Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-05-12 00:00 +0200
        Re: x86_64 Question: Are concurrent IPI requests safe? Thomas Gleixner <tglx@linutronix.de> - 2016-05-11 16:20 +0200

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