Re: [tip:locking/urgent] [jump_label] de752774f3: kernel_BUG_at_arch/x86/kernel/jump_label.c

[Peter Zijlstra <peterz@infradead.org>]

On Sun, Sep 08, 2024 at 09:06:55PM +0800, kernel test robot wrote:
> 
> 
> Hello,
> 
> kernel test robot noticed "kernel_BUG_at_arch/x86/kernel/jump_label.c" on:
> 
> commit: de752774f38bb766941ed1bf910ba5a9f6cc6bf7 ("jump_label: Fix static_key_slow_dec() yet again")
> https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git locking/urgent
> 
> in testcase: boot
> 
> compiler: clang-18
> test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G
> 

> The kernel config and materials to reproduce are available at:
> https://download.01.org/0day-ci/archive/20240908/202409082005.393050e2-oliver.sang@intel.com

So the whole thing actually boots and works on my real machine, so I had
to resort to using this qemu nonsense, as such I did as instructed in
the reproduce file.

I build the thing using clang-17 (for some reason debian is shitting
itself trying to install clang-18 on this machine and I don't want to
spend the day fighting that).

Except, once I do:

  bin/lkp qemu -k /usr/src/linux-2.6/tmp-build/arch/x86/boot/bzImage -m /usr/src/linux-2.6/tmp-build/mod/modules.cgz job-script

The whole thing grinds to a halt like so:

[    4.671842][    T1] /dev/root: Can't open blockdev
[    4.673451][    T1] VFS: Cannot open root device "/dev/ram0" or unknown-block(0,0): error -6
[    4.676062][    T1] Please append a correct "root=" boot option; here are the available partitions:
[    4.678814][    T1] List of all bdev filesystems:
[    4.680333][    T1]  ext3
[    4.680337][    T1]  ext4
[    4.681328][    T1]
[    4.683185][    T1] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
[    4.685856][    T1] CPU: 1 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.11.0-rc3-00004-gde752774f38b #17
[    4.688668][    T1] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[    4.691573][    T1] Call Trace:
[    4.692614][    T1]  <TASK>
[    4.693562][    T1]  dump_stack_lvl+0x3b/0xb0
[    4.694800][    T1]  panic+0x108/0x2e0
[    4.695890][    T1]  mount_root_generic+0x27f/0x300
[    4.697283][    T1]  prepare_namespace+0x72/0xa0
[    4.698547][    T1]  kernel_init_freeable+0x14d/0x190
[    4.699828][    T1]  ? __pfx_kernel_init+0x10/0x10
[    4.701036][    T1]  kernel_init+0x16/0x1a0
[    4.702122][    T1]  ret_from_fork+0x36/0x40
[    4.703275][    T1]  ? __pfx_kernel_init+0x10/0x10
[    4.704424][    T1]  ret_from_fork_asm+0x1a/0x30
[    4.705546][    T1]  </TASK>
[    4.706476][    T1] Kernel Offset: 0x11600000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)

So clearly the day is off to a good start... :/