How does nginx upgrade binaries on the fly?

[codexon]

I am interested in knowing how nginx upgrades binaries on the fly.

http://wiki.nginx.org/NginxCommandLine#Upgrading_To_a_New_Binary_On_The_Fly

What system calls does nginx do to create another master process that can inherit and use the same socket? Can anyone explain or point me to the right place in the source code?

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,42752,42752#msg-42752