The wq_numa_init() function makes a private CPU to node map by calling
cpu_to_node() early in the boot process, before the non-boot CPUs are
brought online.  Since the default implementation of cpu_to_node()
returns zero for CPUs that have never been brought online, the
workqueue system's view is that *all* CPUs are on node zero.

When the unbound workqueue for a non-zero node is created, the
tsk_cpus_allowed() for the worker threads is the empty set because
there are, in the view of the workqueue system, no CPUs on non-zero
nodes.  The code in try_to_wake_up() using this empty cpumask ends up
using the cpumask empty set value of NR_CPUS as an index into the
per-CPU area pointer array, and gets garbage as it is one past the end
of the array.  This results in:

[    0.881970] Unable to handle kernel paging request at virtual address fffffb1008b926a4
[    1.970095] pgd = fffffc00094b0000
[    1.973530] [fffffb1008b926a4] *pgd=0000000000000000, *pud=0000000000000000, *pmd=0000000000000000
[    1.982610] Internal error: Oops: 96000004 [#1] SMP
[    1.987541] Modules linked in:
[    1.990631] CPU: 48 PID: 295 Comm: cpuhp/48 Tainted: G        W       4.8.0-rc6-preempt-vol+ #9
[    1.999435] Hardware name: Cavium ThunderX CN88XX board (DT)
[    2.005159] task: fffffe0fe89cc300 task.stack: fffffe0fe8b8c000
[    2.011158] PC is at try_to_wake_up+0x194/0x34c
[    2.015737] LR is at try_to_wake_up+0x150/0x34c
[    2.020318] pc : [<fffffc00080e7468>] lr : [<fffffc00080e7424>] pstate: 600000c5
[    2.027803] sp : fffffe0fe8b8fb10
[    2.031149] x29: fffffe0fe8b8fb10 x28: 0000000000000000
[    2.036522] x27: fffffc0008c63bc8 x26: 0000000000001000
[    2.041896] x25: fffffc0008c63c80 x24: fffffc0008bfb200
[    2.047270] x23: 00000000000000c0 x22: 0000000000000004
[    2.052642] x21: fffffe0fe89d25bc x20: 0000000000001000
[    2.058014] x19: fffffe0fe89d1d00 x18: 0000000000000000
[    2.063386] x17: 0000000000000000 x16: 0000000000000000
[    2.068760] x15: 0000000000000018 x14: 0000000000000000
[    2.074133] x13: 0000000000000000 x12: 0000000000000000
[    2.079505] x11: 0000000000000000 x10: 0000000000000000
[    2.084879] x9 : 0000000000000000 x8 : 0000000000000000
[    2.090251] x7 : 0000000000000040 x6 : 0000000000000000
[    2.095621] x5 : ffffffffffffffff x4 : 0000000000000000
[    2.100991] x3 : 0000000000000000 x2 : 0000000000000000
[    2.106364] x1 : fffffc0008be4c24 x0 : ffffff0ffffada80
[    2.111737]
[    2.113236] Process cpuhp/48 (pid: 295, stack limit = 0xfffffe0fe8b8c020)
[    2.120102] Stack: (0xfffffe0fe8b8fb10 to 0xfffffe0fe8b90000)
[    2.125914] fb00:                                   fffffe0fe8b8fb80 fffffc00080e7648
.
.
.
[    2.442859] Call trace:
[    2.445327] Exception stack(0xfffffe0fe8b8f940 to 0xfffffe0fe8b8fa70)
[    2.451843] f940: fffffe0fe89d1d00 0000040000000000 fffffe0fe8b8fb10 fffffc00080e7468
[    2.459767] f960: fffffe0fe8b8f980 fffffc00080e4958 ffffff0ff91ab200 fffffc00080e4b64
[    2.467690] f980: fffffe0fe8b8f9d0 fffffc00080e515c fffffe0fe8b8fa80 0000000000000000
[    2.475614] f9a0: fffffe0fe8b8f9d0 fffffc00080e58e4 fffffe0fe8b8fa80 0000000000000000
[    2.483540] f9c0: fffffe0fe8d10000 0000000000000040 fffffe0fe8b8fa50 fffffc00080e5ac4
[    2.491465] f9e0: ffffff0ffffada80 fffffc0008be4c24 0000000000000000 0000000000000000
[    2.499387] fa00: 0000000000000000 ffffffffffffffff 0000000000000000 0000000000000040
[    2.507309] fa20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[    2.515233] fa40: 0000000000000000 0000000000000000 0000000000000000 0000000000000018
[    2.523156] fa60: 0000000000000000 0000000000000000
[    2.528089] [<fffffc00080e7468>] try_to_wake_up+0x194/0x34c
[    2.533723] [<fffffc00080e7648>] wake_up_process+0x28/0x34
[    2.539275] [<fffffc00080d3764>] create_worker+0x110/0x19c
[    2.544824] [<fffffc00080d69dc>] alloc_unbound_pwq+0x3cc/0x4b0
[    2.550724] [<fffffc00080d6bcc>] wq_update_unbound_numa+0x10c/0x1e4
[    2.557066] [<fffffc00080d7d78>] workqueue_online_cpu+0x220/0x28c
[    2.563234] [<fffffc00080bd288>] cpuhp_invoke_callback+0x6c/0x168
[    2.569398] [<fffffc00080bdf74>] cpuhp_up_callbacks+0x44/0xe4
[    2.575210] [<fffffc00080be194>] cpuhp_thread_fun+0x13c/0x148
[    2.581027] [<fffffc00080dfbac>] smpboot_thread_fn+0x19c/0x1a8
[    2.586929] [<fffffc00080dbd64>] kthread+0xdc/0xf0
[    2.591776] [<fffffc0008083380>] ret_from_fork+0x10/0x50
[    2.597147] Code: b00057e1 91304021 91005021 b8626822 (b8606821)
[    2.603464] ---[ end trace 58c0cd36b88802bc ]---
[    2.608138] Kernel panic - not syncing: Fatal exception

Fix by moving call to numa_store_cpu_info() for all CPUs into
smp_prepare_cpus(), which happens before wq_numa_init().  Since
smp_store_cpu_info() now contains only a single function call,
simplify by removing the function and out-lining its contents.
Suggested-by: NRobert Richter <rric@kernel.org>
Fixes: 1a2db300 ("arm64, numa: Add NUMA support for arm64 platforms.")
Cc: <stable@vger.kernel.org> # 4.7.x-
Signed-off-by: NDavid Daney <david.daney@cavium.com>
Reviewed-by: NRobert Richter <rrichter@cavium.com>
Tested-by: NYisheng Xie <xieyisheng1@huawei.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>