Re: [REGRESSION] jump label safety checks break automatic numabalancing

[Steven Rostedt]

FYI, please remove my redhat email from your address book. I don't read
my RH email when I travel (which I've been doing a lot lately).


On Fri, 04 Oct 2013 10:44:00 -0400
Mel Gorman <mgorman@xxxxxxx> wrote:

> With CONFIG_NUMA_BALANCING=y and booting with numa_balancing=enable
> there is a crash very early in the lifetime of the system. By setting
> earlyprintk=ttyS0,115200 the error is visible and looks something like
> this
> 
> [    0.000000] Kernel command line: BOOT_IMAGE=/vmlinuz-3.11.0-vanilla+ root=/dev/sda5 reboot=pci console=tty0 console=ttyS0,115200 numa_balancing=enable earlyprintk=ttyS0,115200
> [    0.000000] Unexpected op at task_numa_fault+0x1d/0xa0 [ffffffff81085ded] (0f 1f 44 00 00) arch/x86/kernel/jump_label.c:53
> PANIC: early exception 06 rip 10:ffffffff815b2663 error 0 cr2 ffff88107ffff000

What's at ffffffff815b2663?

> [    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 3.11.0-vanilla+ #23
> [    0.000000] Hardware name: Dell Inc. PowerEdge R810/0TT6JF, BIOS 2.7.4 04/26/2012
> [    0.000000]  ffffffff81009220 ffffffff81a01e10 ffffffff815b7e7b 00000000000003f8
> [    0.000000]  ffffffff81085ded ffffffff81a01ec8 ffffffff81ad4197 6a2f6c656e72656b
> [    0.000000]  2f3638782f686372 000000000000012b 6562616c5f706d75 ffffffff81c68444
> [    0.000000] Call Trace:
> [    0.000000]  [<ffffffff81009220>] ? alternatives_text_reserved+0x80/0x80
> [    0.000000]  [<ffffffff815b7e7b>] dump_stack+0x55/0x86
> [    0.000000]  [<ffffffff81085ded>] ? task_numa_fault+0x1d/0xa0
> [    0.000000]  [<ffffffff81ad4197>] early_idt_handler+0x77/0xa4
> [    0.000000]  [<ffffffff815b2663>] ? bug_at+0x45/0x47
> [    0.000000]  [<ffffffff815b2663>] ? bug_at+0x45/0x47
> [    0.000000]  [<ffffffff81006db6>] __jump_label_transform.isra.0+0x136/0x150
> [    0.000000]  [<ffffffff81006ea7>] arch_jump_label_transform_static+0x77/0xc0
> [    0.000000]  [<ffffffff81af8596>] jump_label_init+0x81/0xaf
> [    0.000000]  [<ffffffff81ad4c02>] start_kernel+0x161/0x3ce
> [    0.000000]  [<ffffffff81ad48a0>] ? repair_env_string+0x5e/0x5e
> [    0.000000]  [<ffffffff81ad45a5>] x86_64_start_reservations+0x2a/0x2c
> [    0.000000]  [<ffffffff81ad469f>] x86_64_start_kernel+0xf8/0xfc
> [    0.000000] RIP 0x46
> 
> Bisection identified this as the problem commit.
> 
> 9c85f3bdf400665eecf62658a9106501f6a77a13 is the first bad commit
> commit 9c85f3bdf400665eecf62658a9106501f6a77a13
> Author: Steven Rostedt <srostedt@xxxxxxxxxx>
> Date:   Thu Jan 26 18:38:07 2012 -0500
> 
>     x86/jump-label: Add safety checks to jump label conversions
> 
> I did no further investigation yet in case this is already a known
> problem.
> 

We had a similar bug with Xen like this. It ended up being that jump
labels are used before they are initialized, and that is a real bug
too, as the jump labels do not get converted until initialization, and
why would something convert it before then?

-- Steve
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