 | | Because of the problems alluded to in the previous section, 4.2BSD, and later SVR3, introduced reliable signals. The reliable signal mechanism makes two major changes: first, signal dispositions are no longer reset when a signal handler is called. The disposition remains the same until the program explicitly changes it. The second change is the introduction of the ability to block a signal for later delivery. The signal is not delivered to the process immediately, but it is not ignored. The system remembers that the signal occurred, and, if the process ever unblocks the signal, delivers it then. | |
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