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+/*++
+/* NAME
+/* killme_after 3
+/* SUMMARY
+/* programmed death
+/* SYNOPSIS
+/* #include <killme_after.h>
+/*
+/* void killme_after(seconds)
+/* unsigned int seconds;
+/* DESCRIPTION
+/* The killme_after() function does a best effort to terminate
+/* the process after the specified time, should it still exist.
+/* It is meant to be used in a signal handler, as an insurance
+/* against getting stuck somewhere while preparing for exit.
+/* DIAGNOSTICS
+/* None. This routine does a best effort, damn the torpedoes.
+/* LICENSE
+/* .ad
+/* .fi
+/* The Secure Mailer license must be distributed with this software.
+/* AUTHOR(S)
+/* Wietse Venema
+/* IBM T.J. Watson Research
+/* P.O. Box 704
+/* Yorktown Heights, NY 10598, USA
+/*
+/* Wietse Venema
+/* Google, Inc.
+/* 111 8th Avenue
+/* New York, NY 10011, USA
+/*--*/
+
+/* System library. */
+
+#include <sys_defs.h>
+#include <signal.h>
+#include <unistd.h>
+
+/* Utility library. */
+
+#include <killme_after.h>
+
+/* killme_after - self-assured death */
+
+void killme_after(unsigned int seconds)
+{
+ struct sigaction sig_action;
+
+ /*
+ * Schedule an ALARM signal, and make sure the signal will be delivered
+ * even if we are being called from a signal handler and SIGALRM delivery
+ * is blocked.
+ *
+ * Undocumented: when a process runs with PID 1, Linux won't deliver a
+ * signal unless the process specifies a handler (i.e. SIG_DFL is treated
+ * as SIG_IGN). Conveniently, _exit() can be used directly as a signal
+ * handler. This changes the wait status that a parent would see, but in
+ * the case of "init" mode on Linux, no-one would care.
+ */
+ alarm(0);
+ sigemptyset(&sig_action.sa_mask);
+ sig_action.sa_flags = 0;
+ sig_action.sa_handler = (getpid() == 1 ? _exit : SIG_DFL);
+ sigaction(SIGALRM, &sig_action, (struct sigaction *) 0);
+ alarm(seconds);
+ sigaddset(&sig_action.sa_mask, SIGALRM);
+ sigprocmask(SIG_UNBLOCK, &sig_action.sa_mask, (sigset_t *) 0);
+}