Can any kernel gurus out there explain why the final message the kernel
gives upon system shutdown changed from
System halted
in Linux 2.0 to
Power down
in Linux 2.2?
For specificity here is the relevant code from kernel/sys.c for 2.2.12
(pardon me for sending this through the mail, but it will help to make
the discussion more concrete):
/*
* Reboot system call: for obvious reasons only root may call it,
* and even root needs to set up some magic numbers in the registers
* so that some mistake won't make this reboot the whole machine.
* You can also set the meaning of the ctrl-alt-del-key here.
*
* reboot doesn't sync: do that yourself before calling this.
*/
asmlinkage int sys_reboot(int magic1, int magic2, int cmd, void * arg)
{
char buffer[256];
/* We only trust the superuser with rebooting the system. */
if (!capable(CAP_SYS_BOOT))
return -EPERM;
/* For safety, we require "magic" arguments. */
if (magic1 != LINUX_REBOOT_MAGIC1 ||
(magic2 != LINUX_REBOOT_MAGIC2 && magic2 != LINUX_REBOOT_MAGIC2A &&
magic2 != LINUX_REBOOT_MAGIC2B))
return -EINVAL;
lock_kernel();
switch (cmd) {
case LINUX_REBOOT_CMD_RESTART:
notifier_call_chain(&reboot_notifier_list, SYS_RESTART, NULL);
printk(KERN_EMERG "Restarting system.\n");
machine_restart(NULL);
break;
case LINUX_REBOOT_CMD_CAD_ON:
C_A_D = 1;
break;
case LINUX_REBOOT_CMD_CAD_OFF:
C_A_D = 0;
break;
case LINUX_REBOOT_CMD_HALT:
notifier_call_chain(&reboot_notifier_list, SYS_HALT, NULL);
printk(KERN_EMERG "System halted.\n");
machine_halt();
do_exit(0);
break;
case LINUX_REBOOT_CMD_POWER_OFF:
notifier_call_chain(&reboot_notifier_list, SYS_POWER_OFF, NULL);
printk(KERN_EMERG "Power down.\n");
machine_power_off();
do_exit(0);
break;
case LINUX_REBOOT_CMD_RESTART2:
if (strncpy_from_user(&buffer[0], (char *)arg, sizeof(buffer) -
1) < 0) {
unlock_kernel();
return -EFAULT;
}
buffer[sizeof(buffer) - 1] = '\0';
notifier_call_chain(&reboot_notifier_list, SYS_RESTART, buffer);
printk(KERN_EMERG "Restarting system with command '%s'.\n",
buffer);
machine_restart(buffer);
break;
default:
unlock_kernel();
return -EINVAL;
break;
};
unlock_kernel();
return 0;
}
So why does shutdown branch through ...POWER_OFF rather than ...HALT?
At least under a Debian 2.1 (slink)/Linux 2.2.12 combination.
Keith
