3.14.3-rt5: at91: Crash early at boot

[Maxime Ripard <maxime.ripard@free-electrons.com>]

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Hello everyone,

I just gave the latest preempt-rt release for 3.14 a try on an ARM
Atmel SAMA5D3 Xplained board, without any changes to the kernel but
the preempt-rt patches obviously.

The same non-rt version, with the same configuration (except for the
preempt-rt related options), boot fine.

And whenever I boot it, I get:

Uncompressing Linux... done, booting the kernel.
Booting Linux on physical CPU 0x0
Linux version 3.14.3-rt4+ (max@lukather) (gcc version 4.8.2 (Ubuntu/Linaro 4.8.2-16ubuntu4) ) #11 PREEMPT Fri Jun 13 16:03:53 CEST 2014
CPU: ARMv7 Processor [410fc051] revision 1 (ARMv7), cr=10c53c7d
CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing instruction cache
Machine model: SAMA5D3 Xplained
bootconsole [earlycon0] enabled
Memory policy: Data cache writeback
AT91: Detected soc type: sama5d3
AT91: Detected soc subtype: sama5d36
AT91: sram at 0x300000 of 0x20000 mapped at 0xfef58000
CPU: All CPU(s) started in SVC mode.
Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 65024
Kernel command line: console=ttyS0,115200 earlyprintk mtdparts=atmel_nand:256k(at91bootstrap),512k(uboot),256k(env),256k(env-backup),128k(dtb),5m(kernel),2m(rootfs)ro,-(data) root=/dev/nfs ip=dhcp nfsroot=192.168.0.40:/srv/nfs/sysdev rw
PID hash table entries: 1024 (order: 0, 4096 bytes)
Dentry cache hash table entries: 32768 (order: 5, 131072 bytes)
Inode-cache hash table entries: 16384 (order: 4, 65536 bytes)
Memory: 253432K/262144K available (4519K kernel code, 191K rwdata, 1292K rodata, 174K init, 120K bss, 8712K reserved)
Virtual kernel memory layout:
    vector  : 0xffff0000 - 0xffff1000   (   4 kB)
    fixmap  : 0xfff00000 - 0xfffe0000   ( 896 kB)
    vmalloc : 0xd0800000 - 0xff000000   ( 744 MB)
    lowmem  : 0xc0000000 - 0xd0000000   ( 256 MB)
    modules : 0xbf000000 - 0xc0000000   (  16 MB)
      .text : 0xc0008000 - 0xc05b51bc   (5813 kB)
      .init : 0xc05b6000 - 0xc05e1984   ( 175 kB)
      .data : 0xc05e2000 - 0xc0611f60   ( 192 kB)
       .bss : 0xc0611f6c - 0xc06301bc   ( 121 kB)
SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
Preemptible hierarchical RCU implementation.
NR_IRQS:16 nr_irqs:16 16
Unable to handle kernel NULL pointer dereference at virtual address 00000000
pgd = c0004000
[00000000] *pgd=00000000
Internal error: Oops: 5 [#1] PREEMPT ARM
Modules linked in:
CPU: 0 PID: 0 Comm: swapper Not tainted 3.14.3-rt4+ #11
task: c05ecb28 ti: c05e2000 task.ti: c05e2000
PC is at wake_up_process+0x8/0x40
LR is at kthread_create_on_node+0xb0/0x178
pc : [<c003ece0>]    lr : [<c0036318>]    psr: 200001d3
sp : c05e3ef0  ip : 00000017  fp : 00000000
r10: 00000000  r9 : cf4024c0  r8 : ffffffff
r7 : c004cd24  r6 : cf402500  r5 : c05e3f0c  r4 : 00000000
r3 : c06147b0  r2 : 00000001  r1 : cf402554  r0 : 00000000
Flags: nzCv  IRQs off  FIQs off  Mode SVC_32  ISA ARM  Segment kernel
Control: 10c53c7d  Table: 20004059  DAC: 00000015
Process swapper (pid: 0, stack limit = 0xc05e2240)
Stack: (0xc05e3ef0 to 0xc05e4000)
3ee0:                                     c06147b0 cf402540 00000000 c0036318
3f00: 00000000 c004bd38 00000000 00000000 c05e3f10 c05e3f10 00000000 cf404c00
3f20: cf402500 c0318374 00000010 00000010 c004d474 c051dddc 00000010 c055c07c
3f40: 00000104 cf402500 cf404c00 c0318374 00000080 00000010 cf4024c0 c004d808
3f60: cfdf3ca4 c047cefc fefffc00 00000010 cf4024c0 cfffc240 00000000 c05d00ac
3f80: c055c07c cf4024c0 cfdf3ca4 c05e08a0 ffffffff c05ea000 c05daab8 c05cfecc
3fa0: c05ea000 c05e0a28 c05ea000 c0611f80 c05ea000 c05bd9d0 c05d9950 c05b6924
3fc0: ffffffff ffffffff c05b64ec 00000000 00000000 c05daab8 00000000 10c53c7d
3fe0: c05ea01c c05daab4 c05edbd8 20004059 410fc051 20008070 00000000 00000000
Code: e3a05001 eaffffcd e92d4818 e1a04000 (e5903000) 
---[ end trace 3406ff24bd97382e ]---
Kernel panic - not syncing: Attempted to kill the idle task!

Do you know what could be the cause of this, or is this any known issue?

Thanks,
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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