#include <signal.h>
#include <stdbool.h>
#include <stdio.h>
+#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
+#include "poll-loop.h"
#include "shash.h"
+#include "socket-util.h"
#include "util.h"
#define THIS_MODULE VLM_fatal_signal
static struct hook hooks[MAX_HOOKS];
static size_t n_hooks;
-/* Number of nesting signal blockers. */
-static int block_level = 0;
-
-/* Signal mask saved by outermost signal blocker. */
-static sigset_t saved_signal_mask;
+static int signal_fds[2];
+static volatile sig_atomic_t stored_sig_nr = SIG_ATOMIC_MAX;
/* Disabled by fatal_signal_fork()? */
static bool disabled;
-static void call_sigprocmask(int how, sigset_t* new_set, sigset_t* old_set);
+static void fatal_signal_init(void);
static void atexit_handler(void);
static void call_hooks(int sig_nr);
-/* Registers 'hook' to be called when a process termination signal is raised.
- * If 'run_at_exit' is true, 'hook' is also called during normal process
- * termination, e.g. when exit() is called or when main() returns.
- *
- * 'func' will be invoked from an asynchronous signal handler, so it must be
- * written appropriately. For example, it must not call most C library
- * functions, including malloc() or free(). */
-void
-fatal_signal_add_hook(void (*func)(void *aux), void *aux, bool run_at_exit)
-{
- fatal_signal_block();
- assert(n_hooks < MAX_HOOKS);
- hooks[n_hooks].func = func;
- hooks[n_hooks].aux = aux;
- hooks[n_hooks].run_at_exit = run_at_exit;
- n_hooks++;
- fatal_signal_unblock();
-}
-
-/* Blocks program termination signals until fatal_signal_unblock() is called.
- * May be called multiple times with nesting; if so, fatal_signal_unblock()
- * must be called the same number of times to unblock signals.
- *
- * This is needed while adjusting a data structure that will be accessed by a
- * fatal signal hook, so that the hook is not invoked while the data structure
- * is in an inconsistent state. */
-void
-fatal_signal_block(void)
+static void
+fatal_signal_init(void)
{
static bool inited = false;
+
if (!inited) {
size_t i;
inited = true;
+
+ if (pipe(signal_fds)) {
+ ovs_fatal(errno, "could not create pipe");
+ }
+ set_nonblocking(signal_fds[0]);
+ set_nonblocking(signal_fds[1]);
+
sigemptyset(&fatal_signal_set);
for (i = 0; i < ARRAY_SIZE(fatal_signals); i++) {
int sig_nr = fatal_signals[i];
}
atexit(atexit_handler);
}
-
- if (++block_level == 1) {
- call_sigprocmask(SIG_BLOCK, &fatal_signal_set, &saved_signal_mask);
- }
}
-/* Unblocks program termination signals blocked by fatal_signal_block() is
- * called. If multiple calls to fatal_signal_block() are nested,
- * fatal_signal_unblock() must be called the same number of times to unblock
- * signals. */
+/* Registers 'hook' to be called when a process termination signal is raised.
+ * If 'run_at_exit' is true, 'hook' is also called during normal process
+ * termination, e.g. when exit() is called or when main() returns.
+ *
+ * The hook is not called immediately from the signal handler but rather the
+ * next time the poll loop iterates, so it is freed from the usual restrictions
+ * on signal handler functions. */
void
-fatal_signal_unblock(void)
+fatal_signal_add_hook(void (*func)(void *aux), void *aux, bool run_at_exit)
{
- assert(block_level > 0);
- if (--block_level == 0) {
- call_sigprocmask(SIG_SETMASK, &saved_signal_mask, NULL);
- }
+ fatal_signal_init();
+ assert(n_hooks < MAX_HOOKS);
+ hooks[n_hooks].func = func;
+ hooks[n_hooks].aux = aux;
+ hooks[n_hooks].run_at_exit = run_at_exit;
+ n_hooks++;
}
/* Handles fatal signal number 'sig_nr'.
void
fatal_signal_handler(int sig_nr)
{
- call_hooks(sig_nr);
+ ignore(write(signal_fds[1], "", 1));
+ stored_sig_nr = sig_nr;
+}
+
+void
+fatal_signal_run(void)
+{
+ int sig_nr = stored_sig_nr;
- /* Re-raise the signal with the default handling so that the program
- * termination status reflects that we were killed by this signal */
- signal(sig_nr, SIG_DFL);
- raise(sig_nr);
+ if (sig_nr != SIG_ATOMIC_MAX) {
+ call_hooks(sig_nr);
+
+ /* Re-raise the signal with the default handling so that the program
+ * termination status reflects that we were killed by this signal */
+ signal(sig_nr, SIG_DFL);
+ raise(sig_nr);
+ }
+}
+
+void
+fatal_signal_wait(void)
+{
+ poll_fd_wait(signal_fds[0], POLLIN);
}
static void
fatal_signal_add_hook(unlink_files, NULL, true);
}
- fatal_signal_block();
if (!shash_find(&files, file)) {
shash_add(&files, file, NULL);
}
- fatal_signal_unblock();
}
/* Unregisters 'file' from being unlinked when the program terminates via
{
struct shash_node *node;
- fatal_signal_block();
node = shash_find(&files, file);
if (node) {
shash_delete(&files, node);
}
- fatal_signal_unblock();
}
/* Like fatal_signal_remove_file_to_unlink(), but also unlinks 'file'.
do_unlink_files();
}
-/* This is a fatal_signal_add_hook() callback (via unlink_files()). It will be
- * invoked from an asynchronous signal handler, so it cannot call most C
- * library functions (unlink() is an explicit exception, see
- * http://www.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_04.html).
- * That includes free(), so it doesn't try to free the 'files' data
- * structure. */
static void
do_unlink_files(void)
{
signal(sig_nr, SIG_IGN);
}
}
-}
-\f
-static void
-call_sigprocmask(int how, sigset_t* new_set, sigset_t* old_set)
-{
- int error = sigprocmask(how, new_set, old_set);
- if (error) {
- fprintf(stderr, "sigprocmask: %s\n", strerror(errno));
+
+ /* Raise any signals that we have already received with the default
+ * handler. */
+ if (stored_sig_nr != SIG_ATOMIC_MAX) {
+ raise(stored_sig_nr);
}
}
projects / openvswitch / commitdiff