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authorGravatar Denis Vlasenko <vda.linux@googlemail.com>2009-01-31 01:03:45 +0000
committerGravatar Denis Vlasenko <vda.linux@googlemail.com>2009-01-31 01:03:45 +0000
commit72c99af0b44e150a712891f6a3ea7d41827cfffe (patch)
treeefd1f29d140f906deca0e8816e6b50ff2e87a77f
parentcab28aa7de336b0a39ef43ce0eb035a2cab30d4d (diff)
downloadbusybox-72c99af0b44e150a712891f6a3ea7d41827cfffe.tar.gz
busybox-72c99af0b44e150a712891f6a3ea7d41827cfffe.tar.bz2
init: major improvement in documentation and signal handling.
Lots of nasty, but hard to trip, races are fixed. text data bss dec hex filename 1038828 924 10932 1050684 10083c busybox_old 1038787 924 10932 1050643 100813 busybox_unstripped
-rw-r--r--init/init.c671
1 files changed, 374 insertions, 297 deletions
diff --git a/init/init.c b/init/init.c
index 6af6830e4..3a02ece4b 100644
--- a/init/init.c
+++ b/init/init.c
@@ -15,6 +15,7 @@
#include <sys/reboot.h>
#include <sys/resource.h>
+
/* Was a CONFIG_xxx option. A lot of people were building
* not fully functional init by switching it on! */
#define DEBUG_INIT 0
@@ -22,22 +23,53 @@
#define COMMAND_SIZE 256
#define CONSOLE_NAME_SIZE 32
+/* Default sysinit script. */
#ifndef INIT_SCRIPT
-#define INIT_SCRIPT "/etc/init.d/rcS" /* Default sysinit script. */
+#define INIT_SCRIPT "/etc/init.d/rcS"
#endif
-/* Allowed init action types */
+/* Each type of actions can appear many times. They will be
+ * handled in order. RESTART is an exception, only 1st is used.
+ */
+/* Start these actions first and wait for completion */
#define SYSINIT 0x01
-#define RESPAWN 0x02
-/* like respawn, but wait for <Enter> to be pressed on tty: */
-#define ASKFIRST 0x04
-#define WAIT 0x08
-#define ONCE 0x10
+/* Start these after SYSINIT and wait for completion */
+#define WAIT 0x02
+/* Start these after WAIT and *dont* wait for completion */
+#define ONCE 0x04
+/*
+ * NB: while SYSINIT/WAIT/ONCE are being processed,
+ * SIGHUP ("reread /etc/inittab") will be ignored.
+ * Rationale: it would be ambiguous whether SYSINIT/WAIT/ONCE
+ * need to be rerun or not.
+ */
+/* Start these after ONCE are started, restart on exit */
+#define RESPAWN 0x08
+/* Like RESPAWN, but wait for <Enter> to be pressed on tty */
+#define ASKFIRST 0x10
+/*
+ * Start these on SIGINT, and wait for completion.
+ * Then go back to respawning RESPAWN and ASKFIRST actions.
+ * NB: kernel sends SIGINT to us if Ctrl-Alt-Del was pressed.
+ */
#define CTRLALTDEL 0x20
+/*
+ * Start these before killing all processes in preparation for
+ * running RESTART actions or doing low-level halt/reboot/poweroff
+ * (initiated by SIGUSR1/SIGTERM/SIGUSR2).
+ * Wait for completion before proceeding.
+ */
#define SHUTDOWN 0x40
+/*
+ * exec() on SIGQUIT. SHUTDOWN actions are started and waited for,
+ * then all processes are killed, then init exec's 1st RESTART action,
+ * replacing itself by it. If no RESTART action specified,
+ * SIGQUIT has no effect.
+ */
#define RESTART 0x80
-/* Set up a linked list of init_actions, to be read from inittab */
+
+/* A linked list of init_actions, to be read from inittab */
struct init_action {
struct init_action *next;
pid_t pid;
@@ -65,13 +97,6 @@ enum {
static void halt_reboot_pwoff(int sig) NORETURN;
-static void loop_forever(void) NORETURN;
-static void loop_forever(void)
-{
- while (1)
- sleep(1);
-}
-
/* Print a message to the specified device.
* "where" may be bitwise-or'd from L_LOG | L_CONSOLE
* NB: careful, we can be called after vfork!
@@ -241,6 +266,7 @@ static void open_stdio_to_tty(const char* tty_name, int exit_on_failure)
/* empty tty_name means "use init's tty", else... */
if (tty_name[0]) {
int fd;
+
close(STDIN_FILENO);
/* fd can be only < 0 or 0: */
fd = device_open(tty_name, O_RDWR);
@@ -252,7 +278,8 @@ static void open_stdio_to_tty(const char* tty_name, int exit_on_failure)
if (DEBUG_INIT)
_exit(2);
/* NB: we don't reach this if we were called after vfork.
- * Thus halt_reboot_pwoff() itself need not be vfork-safe. */
+ * Thus halt_reboot_pwoff() itself needs not be vfork-safe.
+ */
halt_reboot_pwoff(SIGUSR1); /* halt the system */
}
dup2(STDIN_FILENO, STDOUT_FILENO);
@@ -313,89 +340,37 @@ static void init_exec(const char *command)
static pid_t run(const struct init_action *a)
{
pid_t pid;
- sigset_t nmask, omask;
- /* Block sigchild while forking (why?) */
- sigemptyset(&nmask);
- sigaddset(&nmask, SIGCHLD);
- sigprocmask(SIG_BLOCK, &nmask, &omask);
if (BB_MMU && (a->action_type & ASKFIRST))
pid = fork();
else
pid = vfork();
- sigprocmask(SIG_SETMASK, &omask, NULL);
-
if (pid < 0)
message(L_LOG | L_CONSOLE, "can't fork");
if (pid)
- return pid;
+ return pid; /* Parent or error */
/* Child */
/* Reset signal handlers that were set by the parent process */
+//TODO: block signals across fork(), prevent them to affect child before
+//signals are reset?
bb_signals(0
+ (1 << SIGUSR1)
+ (1 << SIGUSR2)
- + (1 << SIGINT)
+ (1 << SIGTERM)
- + (1 << SIGHUP)
+ (1 << SIGQUIT)
- + (1 << SIGCONT)
- + (1 << SIGSTOP)
+ + (1 << SIGINT)
+ + (1 << SIGHUP)
+ (1 << SIGTSTP)
, SIG_DFL);
- /* Create a new session and make ourself the process
- * group leader */
+ /* Create a new session and make ourself the process group leader */
setsid();
/* Open the new terminal device */
open_stdio_to_tty(a->terminal, 1 /* - exit if open fails */);
-// NB: do not enable unless you change vfork to fork above
-#ifdef BUT_RUN_ACTIONS_ALREADY_DOES_WAITING
- /* If the init Action requires us to wait, then force the
- * supplied terminal to be the controlling tty. */
- if (a->action_type & (SYSINIT | WAIT | CTRLALTDEL | SHUTDOWN | RESTART)) {
- /* Now fork off another process to just hang around */
- pid = fork();
- if (pid < 0) {
- message(L_LOG | L_CONSOLE, "can't fork");
- _exit(EXIT_FAILURE);
- }
-
- if (pid > 0) {
- /* Parent - wait till the child is done */
- bb_signals(0
- + (1 << SIGINT)
- + (1 << SIGTSTP)
- + (1 << SIGQUIT)
- , SIG_IGN);
- signal(SIGCHLD, SIG_DFL);
-
- waitfor(pid);
- /* See if stealing the controlling tty back is necessary */
- if (tcgetpgrp(0) != getpid())
- _exit(EXIT_SUCCESS);
-
- /* Use a temporary process to steal the controlling tty. */
- pid = fork();
- if (pid < 0) {
- message(L_LOG | L_CONSOLE, "can't fork");
- _exit(EXIT_FAILURE);
- }
- if (pid == 0) {
- setsid();
- ioctl(0, TIOCSCTTY, 1);
- _exit(EXIT_SUCCESS);
- }
- waitfor(pid);
- _exit(EXIT_SUCCESS);
- }
- /* Child - fall though to actually execute things */
- }
-#endif
-
/* NB: on NOMMU we can't wait for input in child, so
* "askfirst" will work the same as "respawn". */
if (BB_MMU && (a->action_type & ASKFIRST)) {
@@ -449,21 +424,32 @@ static pid_t run(const struct init_action *a)
static void delete_init_action(struct init_action *action)
{
- struct init_action *a, *b = NULL;
+ struct init_action *a, **nextp;
- for (a = init_action_list; a; b = a, a = a->next) {
+ nextp = &init_action_list;
+ while ((a = *nextp) != NULL) {
if (a == action) {
- if (b == NULL) {
- init_action_list = a->next;
- } else {
- b->next = a->next;
- }
+ *nextp = a->next;
free(a);
break;
}
+ nextp = &a->next;
}
}
+static struct init_action *mark_terminated(int pid)
+{
+ struct init_action *a;
+
+ for (a = init_action_list; a; a = a->next) {
+ if (a->pid == pid) {
+ a->pid = 0;
+ return a;
+ }
+ }
+ return NULL;
+}
+
static void waitfor(pid_t pid)
{
/* waitfor(run(x)): protect against failed fork inside run() */
@@ -472,176 +458,71 @@ static void waitfor(pid_t pid)
/* Wait for any child (prevent zombies from exiting orphaned processes)
* but exit the loop only when specified one has exited. */
- while (wait(NULL) != pid)
- continue;
+ while (1) {
+ pid_t wpid = wait(NULL);
+ mark_terminated(wpid);
+ /* Unsafe. SIGTSTP handler might have wait'ed it already */
+ /*if (wpid == pid) break;*/
+ /* More reliable */
+ if (kill(pid, 0))
+ break;
+ }
}
/* Run all commands of a particular type */
static void run_actions(int action_type)
{
- struct init_action *a, *tmp;
-
- for (a = init_action_list; a; a = tmp) {
- tmp = a->next;
- if (a->action_type & action_type) {
- // Pointless: run() will error out if open of device fails.
- ///* a->terminal of "" means "init's console" */
- //if (a->terminal[0] && access(a->terminal, R_OK | W_OK)) {
- // //message(L_LOG | L_CONSOLE, "Device %s cannot be opened in RW mode", a->terminal /*, strerror(errno)*/);
- // delete_init_action(a);
- //} else
- if (a->action_type & (SYSINIT | WAIT | CTRLALTDEL | SHUTDOWN | RESTART)) {
- waitfor(run(a));
- delete_init_action(a);
- } else if (a->action_type & ONCE) {
- run(a);
- delete_init_action(a);
- } else if (a->action_type & (RESPAWN | ASKFIRST)) {
- /* Only run stuff with pid==0. If they have
- * a pid, that means it is still running */
- if (a->pid == 0) {
- a->pid = run(a);
- }
- }
- }
- }
-}
-
-static void low_level_reboot(unsigned long magic)
-{
- pid_t pid;
- /* We have to fork here, since the kernel calls do_exit(EXIT_SUCCESS) in
- * linux/kernel/sys.c, which can cause the machine to panic when
- * the init process is killed.... */
- pid = vfork();
- if (pid == 0) { /* child */
- reboot(magic);
- _exit(EXIT_SUCCESS);
- }
- waitfor(pid);
-}
-
-static void kill_all_processes(void)
-{
- /* run everything to be run at "shutdown". This is done _prior_
- * to killing everything, in case people wish to use scripts to
- * shut things down gracefully... */
- run_actions(SHUTDOWN);
-
- /* first disable all our signals */
- sigprocmask_allsigs(SIG_BLOCK);
-
- message(L_CONSOLE | L_LOG, "The system is going down NOW!");
-
- /* Allow Ctrl-Alt-Del to reboot system. */
- low_level_reboot(RB_ENABLE_CAD);
-
- /* Send signals to every process _except_ pid 1 */
- message(L_CONSOLE | L_LOG, "Sending SIG%s to all processes", "TERM");
- kill(-1, SIGTERM);
- sync();
- sleep(1);
-
- message(L_CONSOLE | L_LOG, "Sending SIG%s to all processes", "KILL");
- kill(-1, SIGKILL);
- sync();
- sleep(1);
-}
-
-static void halt_reboot_pwoff(int sig)
-{
- const char *m = "halt";
- int rb;
-
- kill_all_processes();
-
- rb = RB_HALT_SYSTEM;
- if (sig == SIGTERM) {
- m = "reboot";
- rb = RB_AUTOBOOT;
- } else if (sig == SIGUSR2) {
- m = "poweroff";
- rb = RB_POWER_OFF;
- }
- message(L_CONSOLE | L_LOG, "Requesting system %s", m);
- /* allow time for last message to reach serial console */
- sleep(2);
- low_level_reboot(rb);
- loop_forever();
-}
-
-/* Handler for QUIT - exec "restart" action,
- * else (no such action defined) do nothing */
-static void restart_handler(int sig UNUSED_PARAM)
-{
struct init_action *a;
for (a = init_action_list; a; a = a->next) {
- if (a->action_type & RESTART) {
- kill_all_processes();
-
- /* unblock all signals (blocked in kill_all_processes()) */
- sigprocmask_allsigs(SIG_UNBLOCK);
-
- /* Open the new terminal device */
- open_stdio_to_tty(a->terminal, 0 /* - halt if open fails */);
+ if (!(a->action_type & action_type))
+ continue;
- messageD(L_CONSOLE | L_LOG, "Trying to re-exec %s", a->command);
- init_exec(a->command);
- sleep(2);
- low_level_reboot(RB_HALT_SYSTEM);
- loop_forever();
+ if (a->action_type & (SYSINIT | WAIT | ONCE | CTRLALTDEL | SHUTDOWN)) {
+ pid_t pid = run(a);
+ if (a->action_type & (SYSINIT | WAIT | CTRLALTDEL | SHUTDOWN))
+ waitfor(pid);
+ }
+ if (a->action_type & (RESPAWN | ASKFIRST)) {
+ /* Only run stuff with pid == 0. If pid != 0,
+ * it is already running
+ */
+ if (a->pid == 0)
+ a->pid = run(a);
}
}
}
-static void ctrlaltdel_signal(int sig UNUSED_PARAM)
-{
- run_actions(CTRLALTDEL);
-}
-
-/* The SIGCONT handler is set to record_signo().
- * It just sets bb_got_signal = SIGCONT. */
-
-/* The SIGSTOP & SIGTSTP handler */
-static void stop_handler(int sig UNUSED_PARAM)
-{
- int saved_errno = errno;
-
- bb_got_signal = 0;
- while (bb_got_signal == 0)
- pause();
-
- errno = saved_errno;
-}
-
static void new_init_action(uint8_t action_type, const char *command, const char *cons)
{
- struct init_action *a, *last;
-
-// Why?
-// if (strcmp(cons, bb_dev_null) == 0 && (action & ASKFIRST))
-// return;
-
- /* Append to the end of the list */
- for (a = last = init_action_list; a; a = a->next) {
- /* don't enter action if it's already in the list,
- * but do overwrite existing actions */
+ struct init_action *a, **nextp;
+
+//BUG
+//old:
+//::shutdown:umount -a -r
+//::shutdown:swapoff -a
+//new: swapped:
+//::shutdown:swapoff -a
+//::shutdown:umount -a -r
+//on SIGHUP, new one will be loaded, but order will be wrong.
+ nextp = &init_action_list;
+ while ((a = *nextp) != NULL) {
+ /* Don't enter action if it's already in the list,
+ * just overwrite existing one's type.
+ * This prevents losing running RESPAWNs.
+ */
if ((strcmp(a->command, command) == 0)
&& (strcmp(a->terminal, cons) == 0)
) {
a->action_type = action_type;
return;
}
- last = a;
+ nextp = &a->next;
}
+ /* Append to the end of the list */
a = xzalloc(sizeof(*a));
- if (last) {
- last->next = a;
- } else {
- init_action_list = a;
- }
+ *nextp = a;
a->action_type = action_type;
safe_strncpy(a->command, command, sizeof(a->command));
safe_strncpy(a->terminal, cons, sizeof(a->terminal));
@@ -665,7 +546,7 @@ static void parse_inittab(void)
if (parser == NULL)
#endif
{
- /* No inittab file -- set up some default behavior */
+ /* No inittab file - set up some default behavior */
/* Reboot on Ctrl-Alt-Del */
new_init_action(CTRLALTDEL, "reboot", "");
/* Umount all filesystems on halt/reboot */
@@ -694,7 +575,7 @@ static void parse_inittab(void)
PARSE_NORMAL & ~(PARSE_TRIM | PARSE_COLLAPSE))) {
/* order must correspond to SYSINIT..RESTART constants */
static const char actions[] ALIGN1 =
- "sysinit\0""respawn\0""askfirst\0""wait\0""once\0"
+ "sysinit\0""wait\0""once\0""respawn\0""askfirst\0"
"ctrlaltdel\0""shutdown\0""restart\0";
int action;
char *tty = token[0];
@@ -722,14 +603,172 @@ static void parse_inittab(void)
#endif
}
+static void low_level_reboot(unsigned magic) NORETURN;
+static void low_level_reboot(unsigned magic)
+{
+ pid_t pid;
+
+ /* Allow time for last message to reach serial console, etc */
+ sleep(1);
+
+ /* We have to fork here, since the kernel calls do_exit(EXIT_SUCCESS)
+ * in linux/kernel/sys.c, which can cause the machine to panic when
+ * the init process exits... */
+ pid = vfork();
+ if (pid == 0) { /* child */
+ reboot(magic);
+ _exit(EXIT_SUCCESS);
+ }
+ waitfor(pid);
+ while (1)
+ sleep(1);
+}
+
+static void kill_all_processes(void)
+{
+ /* Run everything to be run at "shutdown". This is done _prior_
+ * to killing everything, in case people wish to use scripts to
+ * shut things down gracefully... */
+ run_actions(SHUTDOWN);
+
+ message(L_CONSOLE | L_LOG, "The system is going down NOW!");
+
+ /* Allow Ctrl-Alt-Del to reboot system. */
+ reboot(RB_ENABLE_CAD); /* misnomer */
+
+ /* Send signals to every process _except_ pid 1 */
+ message(L_CONSOLE | L_LOG, "Sending SIG%s to all processes", "TERM");
+ kill(-1, SIGTERM);
+ sync();
+ sleep(1);
+
+ message(L_CONSOLE, "Sending SIG%s to all processes", "KILL");
+ kill(-1, SIGKILL);
+ sync();
+ sleep(1);
+}
+
+/* Signal handling by init:
+ *
+ * For process with PID==1, on entry kernel sets all signals to SIG_DFL
+ * and unmasks all signals. However, for process with PID==1,
+ * default action (SIG_DFL) on any signal is to ignore it,
+ * even for special signals SIGKILL and SIGCONT.
+ * (SIGSTOP is still handled specially, at least in 2.6.20)
+ * Also, any signal can be caught or blocked.
+ *
+ * We install two kinds of handlers, "immediate" and "delayed".
+ *
+ * Immediate handlers execute at any time, even while, say, sysinit
+ * is running.
+ *
+ * Delayed handlers just set a flag variable. The variable is checked
+ * in the main loop and acted upon.
+ *
+ * halt/poweroff/reboot and restart have immediate handlers.
+ * They only traverse linked list of struct action's, never modify it,
+ * this should be safe to do even in signal handler. Also they
+ * never return.
+ *
+ * SIGSTOP and SIGTSTP have immediate handlers. They just wait
+ * for SIGCONT to happen.
+ *
+ * SIGHUP has a delayed handler, because modifying linked list
+ * of struct action's from a signal handler while it is manipulated
+ * by the program may be disastrous.
+ *
+ * Ctrl-Alt-Del has a delayed handler. Not a must, but allowing
+ * it to happen even somewhere inside "sysinit" would be a bit awkward.
+ *
+ * There is a tiny probability that SIGHUP and Ctrl-Alt-Del will collide
+ * and only one will be remebered and acted upon.
+ */
+
+static void halt_reboot_pwoff(int sig)
+{
+ const char *m;
+ unsigned rb;
+
+ kill_all_processes();
+
+ m = "halt";
+ rb = RB_HALT_SYSTEM;
+ if (sig == SIGTERM) {
+ m = "reboot";
+ rb = RB_AUTOBOOT;
+ } else if (sig == SIGUSR2) {
+ m = "poweroff";
+ rb = RB_POWER_OFF;
+ }
+ message(L_CONSOLE, "Requesting system %s", m);
+ low_level_reboot(rb);
+ /* not reached */
+}
+
+/* The SIGSTOP/SIGTSTP handler
+ * NB: inside it, all signals except SIGCONT are masked
+ * via appropriate setup in sigaction().
+ */
+static void stop_handler(int sig UNUSED_PARAM)
+{
+ int saved_errno;
+ smallint saved_bb_got_signal;
+
+ saved_errno = errno;
+ saved_bb_got_signal = bb_got_signal;
+ signal(SIGCONT, record_signo);
+
+ while (1) {
+ pid_t wpid;
+
+ if (bb_got_signal == SIGCONT)
+ break;
+ /* NB: this can accidentally wait() for a process
+ * which we waitfor() elsewhere! waitfor() must have
+ * code which is resilient against this.
+ */
+ wpid = wait_any_nohang(NULL);
+ if (wpid > 0)
+ mark_terminated(wpid);
+ sleep(1);
+ }
+
+ signal(SIGCONT, SIG_DFL);
+ bb_got_signal = saved_bb_got_signal;
+ errno = saved_errno;
+}
+
+/* Handler for QUIT - exec "restart" action,
+ * else (no such action defined) do nothing */
+static void restart_handler(int sig UNUSED_PARAM)
+{
+ struct init_action *a;
+
+ for (a = init_action_list; a; a = a->next) {
+ if (!(a->action_type & RESTART))
+ continue;
+
+ /* Starting from here, we won't return.
+ * Thus don't need to worry about preserving errno
+ * and such.
+ */
+ kill_all_processes();
+ open_stdio_to_tty(a->terminal, 0 /* - halt if open fails */);
+ messageD(L_CONSOLE, "Trying to re-exec %s", a->command);
+ init_exec(a->command);
+ low_level_reboot(RB_HALT_SYSTEM);
+ /* not reached */
+ }
+}
+
#if ENABLE_FEATURE_USE_INITTAB
-static void reload_inittab(int sig UNUSED_PARAM)
+static void reload_inittab(void)
{
struct init_action *a, *tmp;
message(L_LOG, "reloading /etc/inittab");
- /* disable old entrys */
+ /* Disable old entries */
for (a = init_action_list; a; a = a->next) {
a->action_type = ONCE;
}
@@ -738,47 +777,57 @@ static void reload_inittab(int sig UNUSED_PARAM)
if (ENABLE_FEATURE_KILL_REMOVED) {
/* Be nice and send SIGTERM first */
- for (a = init_action_list; a; a = a->next) {
- pid_t pid = a->pid;
- if ((a->action_type & ONCE) && pid != 0) {
- kill(pid, SIGTERM);
- }
- }
+ for (a = init_action_list; a; a = a->next)
+ if (a->pid != 0)
+ kill(a->pid, SIGTERM);
#if CONFIG_FEATURE_KILL_DELAY
/* NB: parent will wait in NOMMU case */
if ((BB_MMU ? fork() : vfork()) == 0) { /* child */
sleep(CONFIG_FEATURE_KILL_DELAY);
- for (a = init_action_list; a; a = a->next) {
- pid_t pid = a->pid;
- if ((a->action_type & ONCE) && pid != 0) {
- kill(pid, SIGKILL);
- }
- }
+ for (a = init_action_list; a; a = a->next)
+ if (a->pid != 0)
+ kill(a->pid, SIGKILL);
_exit(EXIT_SUCCESS);
}
#endif
}
- /* remove unused entrys */
+ /* Remove old and unused entries */
for (a = init_action_list; a; a = tmp) {
tmp = a->next;
- if ((a->action_type & (ONCE | SYSINIT | WAIT)) && a->pid == 0) {
+ if (a->action_type & (ONCE | SYSINIT | WAIT))
delete_init_action(a);
- }
}
- run_actions(RESPAWN | ASKFIRST);
+ /* Not needed: */
+ /* run_actions(RESPAWN | ASKFIRST); */
+ /* - we return to main loop, which does this automagically */
}
-#else
-void reload_inittab(int sig);
#endif
+static int check_delayed_sigs(void)
+{
+ int sigs_seen = 0;
+
+ while (1) {
+ smallint sig = bb_got_signal;
+
+ if (!sig)
+ return sigs_seen;
+ bb_got_signal = 0;
+ sigs_seen = 1;
+#if ENABLE_FEATURE_USE_INITTAB
+ if (sig == SIGHUP)
+ reload_inittab();
+#endif
+ if (sig == SIGINT)
+ run_actions(CTRLALTDEL);
+ }
+}
+
int init_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int init_main(int argc UNUSED_PARAM, char **argv)
{
- struct init_action *a;
- pid_t wpid;
-
- die_sleep = 30 * 24*60*60; /* if xmalloc will ever die... */
+ die_sleep = 30 * 24*60*60; /* if xmalloc would ever die... */
if (argv[1] && !strcmp(argv[1], "-q")) {
return kill(1, SIGHUP);
@@ -791,28 +840,9 @@ int init_main(int argc UNUSED_PARAM, char **argv)
) {
bb_show_usage();
}
- /* Set up sig handlers -- be sure to
- * clear all of these in run() */
-// TODO: handlers should just set a flag variable.
-// Move signal handling from handlers to main loop -
-// we have bad races otherwise.
-// E.g. parse_inittab() vs. delete_init_action()...
- signal(SIGQUIT, restart_handler);
- bb_signals(0
- + (1 << SIGUSR1) /* halt */
- + (1 << SIGUSR2) /* poweroff */
- + (1 << SIGTERM) /* reboot */
- , halt_reboot_pwoff);
- signal(SIGINT, ctrlaltdel_signal);
- signal(SIGCONT, record_signo);
- bb_signals(0
- + (1 << SIGSTOP)
- + (1 << SIGTSTP)
- , stop_handler);
-
- /* Turn off rebooting via CTL-ALT-DEL -- we get a
+ /* Turn off rebooting via CTL-ALT-DEL - we get a
* SIGINT on CAD so we can shut things down gracefully... */
- low_level_reboot(RB_DISABLE_CAD);
+ reboot(RB_DISABLE_CAD); /* misnomer */
}
/* Figure out where the default console should be */
@@ -857,11 +887,11 @@ int init_main(int argc UNUSED_PARAM, char **argv)
/* Start a shell on console */
new_init_action(RESPAWN, bb_default_login_shell, "");
} else {
- /* Not in single user mode -- see what inittab says */
+ /* Not in single user mode - see what inittab says */
/* NOTE that if CONFIG_FEATURE_USE_INITTAB is NOT defined,
* then parse_inittab() simply adds in some default
- * actions(i.e., runs INIT_SCRIPT and then starts a pair
+ * actions(i.e., INIT_SCRIPT and a pair
* of "askfirst" shells */
parse_inittab();
}
@@ -888,44 +918,91 @@ int init_main(int argc UNUSED_PARAM, char **argv)
while (*++argv)
memset(*argv, 0, strlen(*argv));
- /* Now run everything that needs to be run */
+ /* Set up signal handlers */
+ if (!DEBUG_INIT) {
+ struct sigaction sa;
+ bb_signals(0
+ + (1 << SIGUSR1) /* halt */
+ + (1 << SIGTERM) /* reboot */
+ + (1 << SIGUSR2) /* poweroff */
+ , halt_reboot_pwoff);
+ signal(SIGQUIT, restart_handler); /* re-exec another init */
+
+ /* Stop handler must allow only SIGCONT inside itself */
+ memset(&sa, 0, sizeof(sa));
+ sigfillset(&sa.sa_mask);
+ sigdelset(&sa.sa_mask, SIGCONT);
+ sa.sa_handler = stop_handler;
+ /* NB: sa_flags doesn't have SA_RESTART.
+ * It must be able to interrupt wait().
+ */
+ sigaction_set(SIGTSTP, &sa); /* pause */
+ /* Does not work as intended, at least in 2.6.20.
+ * SIGSTOP is simply ignored by init:
+ */
+ sigaction_set(SIGSTOP, &sa); /* pause */
+
+ /* SIGINT (Ctrl-Alt-Del) must interrupt wait(),
+ * setting handler without SA_RESTART flag.
+ */
+ bb_signals_recursive_norestart((1 << SIGINT), record_signo);
+ }
+
+ /* Now run everything that needs to be run */
/* First run the sysinit command */
run_actions(SYSINIT);
-
+ check_delayed_sigs();
/* Next run anything that wants to block */
run_actions(WAIT);
-
+ check_delayed_sigs();
/* Next run anything to be run only once */
run_actions(ONCE);
- /* Redefine SIGHUP to reread /etc/inittab */
- signal(SIGHUP, ENABLE_FEATURE_USE_INITTAB ? reload_inittab : SIG_IGN);
+ /* Set up "reread /etc/inittab" handler.
+ * Handler is set up without SA_RESTART, it will interrupt syscalls.
+ */
+ if (!DEBUG_INIT && ENABLE_FEATURE_USE_INITTAB)
+ bb_signals_recursive_norestart((1 << SIGHUP), record_signo);
- /* Now run the looping stuff for the rest of forever */
+ /* Now run the looping stuff for the rest of forever.
+ * NB: if delayed signal happened, avoid blocking in wait().
+ */
while (1) {
- /* run the respawn/askfirst stuff */
+ pid_t wpid;
+ int got_sigs;
+
+ got_sigs = check_delayed_sigs();
+
+ /* (Re)run the respawn/askfirst stuff */
run_actions(RESPAWN | ASKFIRST);
- /* Don't consume all CPU time -- sleep a bit */
+ got_sigs |= check_delayed_sigs();
+
+ /* Don't consume all CPU time - sleep a bit */
sleep(1);
- /* Wait for any child process to exit */
+ got_sigs |= check_delayed_sigs();
+
+ /* Wait for any child process to exit.
+ * NB: "delayed" signals will also interrupt this wait(),
+ * bb_signals_recursive_norestart() set them up for that.
+ * This guarantees we won't be stuck here
+ * till next orphan dies.
+ */
+ if (got_sigs)
+ goto dont_block;
wpid = wait(NULL);
while (wpid > 0) {
- /* Find out who died and clean up their corpse */
- for (a = init_action_list; a; a = a->next) {
- if (a->pid == wpid) {
- /* Set the pid to 0 so that the process gets
- * restarted by run_actions() */
- a->pid = 0;
- message(L_LOG, "process '%s' (pid %d) exited. "
- "Scheduling for restart.",
- a->command, wpid);
- }
+ struct init_action *a = mark_terminated(wpid);
+ if (a) {
+ message(L_LOG, "process '%s' (pid %d) exited. "
+ "Scheduling for restart.",
+ a->command, wpid);
}
- /* see if anyone else is waiting to be reaped */
+ /* See if anyone else is waiting to be reaped */
+ dont_block:
wpid = wait_any_nohang(NULL);
}
- }
+ } /* while (1) */
}