Fix race in pselect replacement code.
On the second and subsequent calls to pselect the notify_pipe was not added to the select readset, opening up a race that om G. Christensen discovered on multiprocessor Solaris <=9 systems. Also reinitialize notify_pipe if the pid changes. This will prevent a parent and child from using the same FD, although this is not an issue in the current structure it might be in future.
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@ -73,6 +73,7 @@ notify_setup_fd(int *fd)
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* we write to this pipe if a SIGCHLD is caught in order to avoid
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* the race between select() and child_terminated
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*/
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static pid_t notify_pid;
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static int notify_pipe[2];
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static void
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notify_setup(void)
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@ -81,6 +82,15 @@ notify_setup(void)
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if (initialized)
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return;
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if (notify_pid == 0)
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debug3_f("initializing");
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else {
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debug3_f("pid changed, reinitializing");
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if (notify_pipe[0] != -1)
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close(notify_pipe[0]);
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if (notify_pipe[1] != -1)
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close(notify_pipe[1]);
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}
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if (pipe(notify_pipe) == -1) {
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error("pipe(notify_pipe) failed %s", strerror(errno));
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} else if (notify_setup_fd(¬ify_pipe[0]) == -1 ||
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@ -91,6 +101,9 @@ notify_setup(void)
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} else {
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set_nonblock(notify_pipe[0]);
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set_nonblock(notify_pipe[1]);
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notify_pid = getpid();
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debug3_f("pid %d saved %d pipe0 %d pipe1 %d", getpid(),
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notify_pid, notify_pipe[0], notify_pipe[1]);
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initialized = 1;
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return;
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}
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@ -159,15 +172,16 @@ pselect(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
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if (sig == SIGKILL || sig == SIGSTOP || sigismember(mask, sig))
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continue;
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if (sigaction(sig, NULL, &sa) == 0 &&
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sa.sa_handler != SIG_IGN && sa.sa_handler != SIG_DFL &&
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sa.sa_handler != sig_handler) {
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sa.sa_handler != SIG_IGN && sa.sa_handler != SIG_DFL) {
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unmasked = 1;
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if (sa.sa_handler == sig_handler)
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continue;
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sa.sa_handler = sig_handler;
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if (sigaction(sig, &sa, &osa) == 0) {
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debug3_f("installing signal handler for %s, "
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"previous %p", strsignal(sig),
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osa.sa_handler);
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saved_sighandler[sig] = osa.sa_handler;
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unmasked = 1;
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}
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}
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}
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@ -183,7 +197,8 @@ pselect(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
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saved_errno = errno;
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sigprocmask(SIG_SETMASK, &osig, NULL);
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notify_done(readfds);
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if (unmasked)
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notify_done(readfds);
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errno = saved_errno;
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return ret;
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}
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