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authorGravatar Denys Vlasenko <vda.linux@googlemail.com>2018-02-19 15:52:35 +0100
committerGravatar Denys Vlasenko <vda.linux@googlemail.com>2018-02-19 15:52:35 +0100
commit95121d98e6da12599246d8e25c3f300e422a06fb (patch)
treedcdb5306ba795ceccb9c435967ff535a949c3422
parent7398892ac0592999397532ba168376edd402438c (diff)
downloadbusybox-95121d98e6da12599246d8e25c3f300e422a06fb.tar.gz
busybox-95121d98e6da12599246d8e25c3f300e422a06fb.tar.bz2
poweroff: add a config option for people needing VERY early poweroff
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
-rw-r--r--init/halt.c54
1 files changed, 54 insertions, 0 deletions
diff --git a/init/halt.c b/init/halt.c
index c6c857f08..e6dcb1c67 100644
--- a/init/halt.c
+++ b/init/halt.c
@@ -24,6 +24,17 @@
//config: help
//config: Stop all processes and reboot the system.
//config:
+//config:config FEATURE_WAIT_FOR_INIT
+//config: bool "Before signaling init, make sure it is ready for it"
+//config: default y
+//config: depends on HALT || POWEROFF || REBOOT
+//config: help
+//config: In rare cases, poweroff may be commanded by firmware to OS
+//config: even before init process exists. On Linux, this spawns
+//config: "/sbin/poweroff" very early. This option adds code
+//config: which checks that init is ready to receive poweroff
+//config: commands. Code size increase of ~80 bytes.
+//config:
//config:config FEATURE_CALL_TELINIT
//config: bool "Call telinit on shutdown and reboot"
//config: default y
@@ -108,6 +119,47 @@ static void write_wtmp(void)
#define write_wtmp() ((void)0)
#endif
+#if ENABLE_FEATURE_WAIT_FOR_INIT
+/* In Linux, "poweroff" may be spawned even before init.
+ * For example, with ACPI:
+ * linux/drivers/acpi/bus.c:
+ * static void sb_notify_work(struct work_struct *dummy)
+ * orderly_poweroff(true);
+ * linux/kernel/reboot.c:
+ * static int run_cmd(const char *cmd)
+ * ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
+ * poweroff_cmd[] = "/sbin/poweroff";
+ * static int __orderly_poweroff(bool force)
+ * ret = run_cmd(poweroff_cmd);
+ *
+ * We want to make sure init exists and listens to signals.
+ */
+static int init_was_not_there(void)
+{
+ enum { initial = 5 }; /* 5 seconds should be plenty for timeout */
+ int cnt = initial - 1;
+
+ /* Just existence of PID 1 does not mean it installed
+ * the handlers already.
+ */
+#if 0
+ while (kill(1, 0) != 0 && --cnt >= 0)
+ sleep(1);
+#endif
+ /* ... so let's wait for some evidence a usual startup event,
+ * mounting of /proc, happened. By that time init should be ready
+ * for signals.
+ */
+ while (access("/proc/meminfo", F_OK) != 0 && --cnt >= 0)
+ sleep(1);
+
+ /* Does it look like init wasn't there? */
+ return (cnt != initial - 1);
+}
+#else
+ /* Assume it's always there */
+# define init_was_not_there() 0
+#endif
int halt_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int halt_main(int argc UNUSED_PARAM, char **argv)
@@ -171,6 +223,8 @@ int halt_main(int argc UNUSED_PARAM, char **argv)
if (!ENABLE_FEATURE_CALL_TELINIT) {
/* bbox init assumed */
rc = kill(1, signals[which]);
+ if (init_was_not_there())
+ rc = kill(1, signals[which]);
} else {
/* SysV style init assumed */
/* runlevels: