This traces standard and real-time signals generated system wide. This is done by instrumenting signal/signal_generate tracepoints.
$ sudo ./sigsnoop.bt Attaching 9 probes... Tracing signals, hit ctrl-c to end. TIME PID COMM TPID SIG 09:42:33 214863 locate 214860 SIGCHLD 09:42:33 214866 locate 214860 SIGCHLD 09:42:33 214862 rpm 214861 SIGCHLD 09:42:33 214868 rpm 214861 SIGCHLD 09:42:33 214869 rpm 214861 SIGCHLD 09:42:33 214870 uname 214861 SIGCHLD 09:42:34 214879 rpm 214874 SIGCHLD
The first line shows that pid 214863 (locate thread) delivered a SIGCHLD signal to pid 214860 (TPID = the target pid).