Import from old repository commit 61ef2b42a9c4ba8e1600f15bb0236765edc2ad45.

lib/signals.c

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+/*
+ * Copyright (c) 2008, 2009 Nicira Networks.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <config.h>
+#include "signals.h"
+#include <assert.h>
+#include <errno.h>
+#include <limits.h>
+#include <signal.h>
+#include <unistd.h>
+#include "poll-loop.h"
+#include "socket-util.h"
+#include "util.h"
+
+#if defined(_NSIG)
+#define N_SIGNALS _NSIG
+#elif defined(NSIG)
+#define N_SIGNALS NSIG
+#else
+/* We could try harder to get the maximum signal number, but in practice we
+ * only care about SIGHUP, which is normally signal 1 anyway. */
+#define N_SIGNALS 32
+#endif
+
+struct signal {
+    int signr;
+};
+
+static volatile sig_atomic_t signaled[N_SIGNALS];
+
+static int fds[2];
+
+static void signal_handler(int signr);
+
+/* Initializes the signals subsystem (if it is not already initialized).  Calls
+ * exit() if initialization fails.
+ *
+ * Calling this function is optional; it will be called automatically by
+ * signal_start() if necessary.  Calling it explicitly allows the client to
+ * prevent the process from exiting at an unexpected time. */
+void
+signal_init(void)
+{
+    static bool inited;
+    if (!inited) {
+        inited = true;
+        if (pipe(fds)) {
+            ovs_fatal(errno, "could not create pipe");
+        }
+        set_nonblocking(fds[0]);
+        set_nonblocking(fds[1]);
+    }
+}
+
+/* Sets up a handler for 'signr' and returns a structure that represents it.
+ *
+ * Only one handler for a given signal may be registered at a time. */
+struct signal *
+signal_register(int signr)
+{
+    struct sigaction sa;
+    struct signal *s;
+
+    signal_init();
+
+    /* Set up signal handler. */
+    assert(signr >= 1 && signr < N_SIGNALS);
+    memset(&sa, 0, sizeof sa);
+    sa.sa_handler = signal_handler;
+    sigemptyset(&sa.sa_mask);
+    sa.sa_flags = SA_RESTART;
+    if (sigaction(signr, &sa, NULL)) {
+        ovs_fatal(errno, "sigaction(%d) failed", signr);
+    }
+
+    /* Return structure. */
+    s = xmalloc(sizeof *s);
+    s->signr = signr;
+    return s;
+}
+
+/* Returns true if signal 's' has been received since the last call to this
+ * function with argument 's'. */
+bool
+signal_poll(struct signal *s)
+{
+    char buf[_POSIX_PIPE_BUF];
+    read(fds[0], buf, sizeof buf);
+    if (signaled[s->signr]) {
+        signaled[s->signr] = 0;
+        return true;
+    }
+    return false;
+}
+
+/* Causes the next call to poll_block() to wake up when signal_poll(s) would
+ * return true. */
+void
+signal_wait(struct signal *s)
+{
+    if (signaled[s->signr]) {
+        poll_immediate_wake();
+    } else {
+        poll_fd_wait(fds[0], POLLIN);
+    }
+}
+
+static void
+signal_handler(int signr)
+{
+    if (signr >= 1 && signr < N_SIGNALS) {
+        write(fds[1], "", 1);
+        signaled[signr] = true;
+    }
+}