bt subcommand of crash occasionally does not output the backtrace normally

Issue

• This problem occurred with one vmcore in every 120 vmcores and the following warning message was displayed.

crash> bt -a
PID: 14927  TASK: ffff810059a310c0  CPU: 0   COMMAND: "dd"
 #0 [ffffffff80449f20] crash_nmi_callback at ffffffff8007bf40
 #1 [ffffffff80449f40] do_nmi at ffffffff8006688a
 #2 [ffffffff80449f50] nmi at ffffffff80065eef
    [exception RIP: system_call+3]
    RIP: ffffffff8005e09b  RSP: 00007fff6fe74978  RFLAGS: 00000046
    RAX: 0000000000000005  RBX: 000000001a185030  RCX: 00002b3f3d1540a4
    RDX: 00007fff6fe74980  RSI: 00007fff6fe74980  RDI: 0000000000000001
    RBP: 000000001a185030   R8: 0000000000000001   R9: 0000000000000000
    R10: 0000000000000000  R11: 0000000000000246  R12: 000000000000018f
    R13: 00007fff6fe74b50  R14: 000000001a185030  R15: 000000000000000a
    ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
bt: WARNING: possibly bogus exception frame     
--- <NMI exception stack> ---
 #3 [7fff6fe74978] system_call at ffffffff8005e09b
bt: cannot transition from exception stack to current process stack:
    exception stack pointer: ffffffff80449f20
      process stack pointer: 7fff6fe74978
         current stack base: ffff81004167a000