why use INP_WLOCK instead of INP_RLOCK

[Jim]

Hi All,

I am not sure if anybody has asked it before. I could not find answer by
doing rough search on Internet, if it is duplicate question, sorry in
advance.

My question is that, for getting socket options in tcp_ctloutput() in
tcp_usrreq.c, why do we need to do lock with INP_WLOCK(inp) as setting
socket options does. Why do we just use INP_RLOCK(inp), as it looks not
changing anything in tcp control block?

Thank you for your kindly answer.

Jim