A driver might be waiting for a condition that cannot occur or will not happen for a long time. In such cases, the user can send a signal to abort the thread. Depending on the driver design, the signal might not cause the driver to wake up.
cv_wait_sig(9F) allows a signal to unblock the thread. This capability enables the user to break out of potentially long waits by sending a signal to the thread with kill(1) or by typing the interrupt character. cv_wait_sig(9F) returns zero if it is returning because of a signal, or nonzero if the condition occurred. However, see Threads Unable to Receive Signals for cases in which signals might not be received.
The following example shows how to use cv_wait_sig(9F) to allow a signal to unblock the thread.
mutex_enter(&xsp->mu); while (xsp->busy) { if (cv_wait_sig(&xsp->cv, &xsp->mu) == 0) { /* Signaled while waiting for the condition */ /* tidy up and exit */ mutex_exit(&xsp->mu); return (EINTR); } } xsp->busy = 1; mutex_exit(&xsp->mu);