There have been many reports of init failing to reboot and/or failing to halt
over the years. Well I finally took the time to track this down. It turns out
that inside linux/kernel/sys.c the kernel will call
machine_halt();
do_exit(0);
when halting, or will call
machine_power_off();
do_exit(0);
during a reboot. Unlike sysv init, we call reboot from within the init
process, so if the call to machine_halt() or machine_power_off() returns, the call to do_exit(0) will cause the kernel to panic. Which is a very
bad thing to happen.
So I just added this little patch to fork and call the reboot
syscall from within the forked child process, thereby neatly
avoiding the problem.
But IMHO, both calls to do_exit(0) within linux/kernel/sys.c
are bugs and should be fixed.
-Erik
diff --git a/init/init.c b/init/init.c
index be91d6a..8adff1c 100644
--- a/init/init.c
+++ b/init/init.c
@@ -46,6 +46,10 @@
#ifdef CONFIG_SYSLOGD
# include <sys/syslog.h>
#endif
+#if (__GNU_LIBRARY__ > 5) || defined(__dietlibc__)
+#include <sys/reboot.h>
+#endif
+
#if defined(__UCLIBC__) && !defined(__UCLIBC_HAS_MMU__)
#define fork vfork
@@ -80,13 +84,6 @@
};
-#if (__GNU_LIBRARY__ > 5) || defined(__dietlibc__)
-#include <sys/reboot.h>
-#define init_reboot(magic) reboot(magic)
-#else
-#define init_reboot(magic) reboot(0xfee1dead, 672274793, magic)
-#endif
-
#ifndef _PATH_STDPATH
#define _PATH_STDPATH "/usr/bin:/bin:/usr/sbin:/sbin"
#endif
@@ -663,6 +660,23 @@
}
#ifndef DEBUG_INIT
+static void init_reboot(unsigned long magic)
+{
+ pid_t pid;
+ /* We have to fork here, since the kernel calls do_exit(0) in
+ * linux/kernel/sys.c, which can cause the machint to panic when
+ * the init process is killed.... */
+ if ((pid = fork()) == 0) {
+#if (__GNU_LIBRARY__ > 5) || defined(__dietlibc__)
+ reboot(magic);
+#else
+ reboot(0xfee1dead, 672274793, magic);
+#endif
+ _exit(0);
+ }
+ waitpid (pid, NULL, 0);
+}
+
static void shutdown_system(void)
{
sigset_t block_signals;