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   pselect.3p    ( 3 )

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Обоснование (Rationale)

In earlier versions of the Single UNIX Specification, the
       select() function was defined in the <sys/time.h> header. This is
       now changed to <sys/select.h>.  The rationale for this change was
       as follows: the introduction of the pselect() function included
       the <sys/select.h> header and the <sys/select.h> header defines
       all the related definitions for the pselect() and select()
       functions. Backwards-compatibility to existing XSI
       implementations is handled by allowing <sys/time.h> to include
       <sys/select.h>.

       Code which wants to avoid the ambiguity of the signal mask for
       thread cancellation handlers can install an additional
       cancellation handler which resets the signal mask to the expected
       value.

           void cleanup(void *arg)
           {
               sigset_t *ss = (sigset_t *) arg;
               pthread_sigmask(SIG_SETMASK, ss, NULL);
           }

           int call_pselect(int nfds, fd_set *readfds, fd_set *writefds,
               fd_set errorfds, const struct timespec *timeout,
               const sigset_t *sigmask)
           {
               sigset_t oldmask;
               int result;
               pthread_sigmask(SIG_SETMASK, NULL, &oldmask);
               pthread_cleanup_push(cleanup, &oldmask);
               result = pselect(nfds, readfds, writefds, errorfds, timeout, sigmask);
               pthread_cleanup_pop(0);
               return result;
           }