95121d98e
Denys Vlasenko
2018-02-19
Subject
poweroff: add a config option for people needing VERY early poweroff
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init/halt.c+54 -0
| @@ -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: | |