From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <0f871b6bb553a56e50fe8af78f564ede@hamnavoe.com>
To: 9fans@9fans.net
From: Richard Miller <9fans@hamnavoe.com>
Date: Tue, 20 Jul 2010 09:54:22 +0100
In-Reply-To: <1fc2ed1667573e0f022d218e80319be2@hamnavoe.com>
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Subject: Re: [9fans] apic fail
Topicbox-Message-UUID: 40d9d46e-ead6-11e9-9d60-3106f5b1d025

> Is one interrupt being dispatched to two cpus, I wonder?

The answer appears to be yes.  I bracketed rtl8169interrupt()
with these lines:

static void
rtl8169interrupt(Ureg*, void* arg)
{
  ...
  static Ref twice;
  if(incref(&twice) != 1) iprint("cpu%d: I see everything twice!\n", m->machno);
  ...
  decref(&twice);
}

The result on rebooting was:

cpu0: I see everything twice!
cpu1: I see everything twice!
cpu0: I see everything twice!
cpu0: I see everything twice!
...

many times over.

As a side effect this stops the kernel from crashing, because while one cpu
is doing its iprint, the other can get on with its interrupt routine safely.