Linux: security: openssh: a situation where sshd appears defunct

I encountered a problem recently, and a pair of legacy processes appeared, similar to the following two
root 77399 19100 77399 0 1 01:46 ? 00:00:00 sshd: \mzhan017 [priv]
sshd 77400 77399 77400 0 1 01 :46 ? 00:00:00 sshd: [defunct]

This is the first time in my life that I encountered this situation. Be sure to record it!

For the explanation of [priv], please refer to: https://mzhan017.blog.csdn.net/article/details/132071406

Finally, the gcore of the 77399 process was taken down!
Use gdb to parse as follows:

#0  __kernel_vsyscall () at arch/x86/entry/vdso/vdso32/system_call.S:72
#1  0