DCE Threads provides the POSIX sigwait( ) service to allow threads to perform activities similar to signal handling without having to deal with signals directly. It also provides a jacket for sigaction( ) that allows each thread to have its own handler for synchronous signals.
In order to provide these mechanisms, DCE Threads installs signal handlers for most of the UNIX signals during initialization.
DCE Threads do not provide handlers for several UNIX signals. Those signals and the reasons why handlers are not provided are shown in the following table.
Signals for Which Handlers Are Not Provided
| Signal | Reason Handler Is Not Provided |
| SIGKILL and SIGSTOP | These signals cannot be caught by user mode code. |
| SIGTRAP | Catching this signal interferes with debugging. |
| SIGTSTP and SIGQUIT | These signals are caught only while a thread has issued a sigwait( ) call because their default actions are otherwise valuable. | More: