Comment # 6 on bug 1208783 from Scott Bahling

I don't see a spinlock:

crash> bt 14517
PID: 14517  TASK: ffff8d228fb3c000  CPU: 4   COMMAND: "jackdbus"
 #0 [fffffe00000f9e50] crash_nmi_callback at ffffffffa4a71853
 #1 [fffffe00000f9e58] nmi_handle at ffffffffa4a3eb85
 #2 [fffffe00000f9e98] default_do_nmi at ffffffffa5436d89
 #3 [fffffe00000f9eb8] exc_nmi at ffffffffa5436fb7
 #4 [fffffe00000f9ef0] end_repeat_nmi at ffffffffa5601658
    [exception RIP: smp_call_function_many_cond+291]
    RIP: ffffffffa4b75833  RSP: ffffb8694d853b88  RFLAGS: 00000202
    RAX: 0000000000000011  RBX: 0000000000000001  RCX: 0000000000000000
    RDX: 0000000000000001  RSI: 0000000000000000  RDI: ffff8d263fa7af40
    RBP: 000000000000000f   R8: 0000000000000000   R9: 0000000000000000
    R10: 000000000000000f  R11: 0000000000000000  R12: ffff8d222ff34a40
    R13: ffff8d222ff34a40  R14: 0000000000000000  R15: 0000000000000014
    ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
--- <NMI exception stack> ---
 #5 [ffffb8694d853b88] smp_call_function_many_cond at ffffffffa4b75833
 #6 [ffffb8694d853c00] on_each_cpu_cond_mask at ffffffffa4b75d05
 #7 [ffffb8694d853c08] flush_tlb_mm_range at ffffffffa4a9563e
 #8 [ffffb8694d853c28] unmap_page_range at ffffffffa4cb9096
 #9 [ffffb8694d853d08] unmap_vmas at ffffffffa4cb9664
#10 [ffffb8694d853d70] unmap_region at ffffffffa4cc2fe8
#11 [ffffb8694d853e30] __do_munmap at ffffffffa4cc5284
#12 [ffffb8694d853e88] __vm_munmap at ffffffffa4cc55fb
#13 [ffffb8694d853ed8] __x64_sys_munmap at ffffffffa4cc56e7
#14 [ffffb8694d853ef0] do_syscall_64 at ffffffffa5435408
#15 [ffffb8694d853f08] syscall_exit_to_user_mode at ffffffffa5439698
#16 [ffffb8694d853f18] do_syscall_64 at ffffffffa5435417
#17 [ffffb8694d853f50] entry_SYSCALL_64_after_hwframe at ffffffffa5600099
    RIP: 00007f9710e33147  RSP: 00007ffce7708968  RFLAGS: 00000202
    RAX: ffffffffffffffda  RBX: 00007f970ed10508  RCX: 00007f9710e33147
    RDX: 0000000000000001  RSI: 000000000000000c  RDI: 00007f9712287000
    RBP: 0000561f9c63f520   R8: 0000000000000000   R9: 00000000ffffffff
    R10: 00007f9710d29468  R11: 0000000000000202  R12: 0000000000000002
    R13: 00007ffce77091b0  R14: 00007ffce77089b0  R15: 0000561f9c64fd40
    ORIG_RAX: 000000000000000b  CS: 0033  SS: 002b