linux-kernel - Re: clockevents_program_event WARN

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Date:	Tue, 30 Apr 2013 17:37:19 -0400
From:	Dave Jones <davej@...hat.com>
To:	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: clockevents_program_event WARN_ON preventing boot.

On Tue, Apr 30, 2013 at 05:20:07PM -0400, Dave Jones wrote:
 > I have a machine that crashes instantly on boot up on Linus'
 > post-3.9 tree. (8c55f1463c1fd318d5e785f02b80bcc32176d342)
 > 
 > By booting with boot_delay=100, I was able to take a photo
 > and capture the top of the trace.  (For some reason, larger boot
 > delay parameters seem to make it take forever before printing
 > even a single character, which made this a pain to debug).
 > 
 > The WARN_ON it prints right before locking up is this in clockevents_program_event
 > 
 > 208         if (unlikely(expires.tv64 < 0)) {
 > 209                 WARN_ON_ONCE(1);
 > 210                 return -ETIME;
 > 211         }
 > 
 > booting with maxcpus=1 avoids the problem.
 > 
 > I'm still trying to get a complete stack trace, though it's painful
 > due to the above reason.

On a second machine, I'm seeing an oops even earlier. As soon as I
exit grub, I get a blinking cursor.  If I boot with earlyprintk=vga
I can see..

Call Trace:
 <IRQ>
  tick_check_oneshot_broadcast
  tick_check_idle
  irq_enter
  do_IRQ
  common_interrupt
 <EOI>
  x86_64_start_reservations
  x86_64_start_kernel
RIP: clockevents_set_mode+0x18

Matching up the Code: line of the trace with the disassembly I see..

        if (dev->mode != mode) {
 4c8:   39 77 38                cmp    %esi,0x38(%rdi)


the comment above that code is telling..

/*
 * Must be called with interrupts disabled !
 */

So how did we get an IRQ ?

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