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From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com
Cc: linux-kernel@vger.kernel.org, x86@kernel.org
Subject: Question about tboot_wait_for_aps()
Date: Tue, 24 Jul 2012 08:58:53 -0700	[thread overview]
Message-ID: <20120724155853.GA32362@linux.vnet.ibm.com> (raw)

Hello!

While taking another pass through the CPU_DYING notifiers, I came upon
the following:

	static int tboot_wait_for_aps(int num_aps)
	{
		unsigned long timeout;

		timeout = AP_WAIT_TIMEOUT*HZ;
		while (atomic_read((atomic_t *)&tboot->num_in_wfs) != num_aps &&
		       timeout) {
			mdelay(1);
			timeout--;
		}

		if (timeout)
			pr_warning("tboot wait for APs timeout\n");

		return !(atomic_read((atomic_t *)&tboot->num_in_wfs) == num_aps);
	}

Questions:

1.	Why AP_WAIT_TIMEOUT*HZ?  Given the mdelay(), shouldn't this
	instead be AP_WAIT_TIMEOUT*1000?  The definition of AP_WAIT_TIMEOUT
	indicates that it is in seconds.

2.	Who changes ->num_in_wfs?  Any other CPUs are in stop_machine(),
	plus I don't see any assignments to this field.  Does the boot
	firmware run again to make this change, sort of like SMIs?

I guess that the good news is that I don't seen anything that cares about
stop_machine().  ;-)

							Thanx, Paul


                 reply	other threads:[~2012-07-24 16:40 UTC|newest]

Thread overview: [no followups] expand[flat|nested]  mbox.gz  Atom feed

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