_lwp_kill() sends the signal specified by
sig to the light-weight process specified by
lwp. If the
sig argument is given as 0 (zero),
_lwp_kill will test for the existence of the target LWP, but will take no further action.
Job control signals and uncatchable signals can not be directed to a specific LWP: if posted with
_lwp_kill, they will affect all LWPs in the process.
Signals will be posted successfully to suspended LWPs, but will not be handled further until the LWP has been continued.