some questions about kernel source

Dear all: I have some questions about kernel source code: 1. in kernel/trace, I always see "__read_mostly" at the end of parameter is that a compiler optimization parameter? 2. what are below __releases and __acquires used for? ehci_urb_done(struct ehci_hcd *ehci, struct urb *urb, int status) __releases(ehci->lock) __acquires(ehci->lock) these 2 cmds are not in the {}, so I guess it will not compile out machine. If so, why we add them after function prototype? -- Regards,