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poweroff: add a config option for people needing VERY early poweroff

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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2018-02-19 15:52:35 +01:00
parent 7398892ac0
commit 95121d98e6
1 changed files with 54 additions and 0 deletions
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54
init/halt.c
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@ -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: