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From: Thomas Gleixner <tglx@linutronix.de>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: peterz@infradead.org, mingo@kernel.org,
	akpm@linux-foundation.org, mgorman@techsingularity.net,
	mhocko@kernel.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org
Subject: Re: x86_64 Question: Are concurrent IPI requests safe?
Date: Mon, 9 May 2016 18:54:14 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.11.1605091853130.3540@nanos> (raw)
In-Reply-To: <201605092354.AHF82313.FtQFOMVOFJLOSH@I-love.SAKURA.ne.jp>

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

  reply	other threads:[~2016-05-09 16:54 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-05-06 10:58 [next-20160506 mm,smp] hang up at csd_lock_wait() from drain_all_pages() Tetsuo Handa
2016-05-09 14:54 ` x86_64 Question: Are concurrent IPI requests safe? Tetsuo Handa
2016-05-09 16:54   ` Thomas Gleixner [this message]
2016-05-11 13:19     ` Tetsuo Handa
2016-05-11 13:39       ` Peter Zijlstra
2016-05-11 14:09         ` Tetsuo Handa
2016-05-11 14:33           ` Thomas Gleixner
2016-05-11 15:19             ` Tetsuo Handa
2016-05-11 17:46               ` Peter Zijlstra
2016-05-11 21:56                 ` Tetsuo Handa
2016-05-11 14:13       ` Thomas Gleixner

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