On Tue, Feb 07, 2012 at 03:35:59PM -0800, Eric W. Biederman wrote: > Vivek Goyal <vgoyal at redhat.com> writes: > > > On Tue, Feb 07, 2012 at 04:57:41PM -0500, Don Zickus wrote: > >> On Thu, Feb 02, 2012 at 03:24:46PM -0800, Eric W. Biederman wrote: > >> > > Eric, brought up a point that because the boot code was restructured we may > >> > > not need to disable the io apic any more in the crash path. The original > >> > > concern that led to the development of disable_IO_APIC, was that the TSC > >> > > calibration on boot up relied on the PIT timer for reference. Access > >> > > to the PIT required 8259 interrupts to be working. This wouldn't work > >> > > if the ioapic needed to be configured. So on panic path, the ioapic was > >> > > reconfigured to use virtual wire mode to allow the 8259 to passthrough. > >> > > >> > A small clarification originally it was the jiffies calibration that > >> > would fail if we could cause the PIT to generate interrupts through the > >> > 8259. The boot would then hang at calibrating jiffies. > >> > >> Ok. Thanks! > > > > So now what has changed? Do we setup LAPIC and IOAPIC early enough to > > receive PIT interrupts in regular mode (non-virtual wire mode) or > > something else? > > Yes. Part of the Moorstown work required that this be done because > moorsetown did not support legacy mode. Last I looked the code hadn't > been generalized beyond Moorsetown but empirically it works now. > > Don as to what to test the only case I can think of that might be spooky > is a screaming interrupt during the handover. You might want to try > playing with lkcdtm to try some of the more exotic crash scenarios. But > all I expect further testing might reveal are places where we are not > as robust in initializing the hardware as we might be. Things that > might have been papered over by the ioapic shutdown. I ran lkdtm by panic'ing in the interrupt handle thus leaving device interrupt un-ack'd and the apic might have been un-ack'd too (jprobes hooked in at do_IRQ). 3 out 3 times the second kernel came up on my core2 quad. Cheers, Don
