Re: [PATCH] disable non-boot CPUs before poweroff

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Mark Lord wrote:

We need to disable all CPUs other than the boot CPU (usually 0)
before attempting to power-off modern SMP machines.
This seems to fix the hang-on-poweroff issue
that one of my SMP boxes exhibits.  More testing required.

Signed-off-by: Mark Lord <[email protected]>
---

--- linux/kernel/sys.c.orig    2007-09-13 09:49:11.000000000 -0400
+++ linux/kernel/sys.c    2007-09-28 09:48:54.000000000 -0400
@@ -32,6 +32,7 @@
#include <linux/getcpu.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/seccomp.h>
+#include <linux/cpu.h>

#include <linux/compat.h>
#include <linux/syscalls.h>
@@ -879,6 +880,7 @@
    if (pm_power_off_prepare)
        pm_power_off_prepare();
    sysdev_shutdown();
+    disable_nonboot_cpus();
    printk(KERN_EMERG "Power down.\n");
    machine_power_off();
}

Okay, verified now.  Prior to this patch, *both* CPUs were still up and running
when machine_power_off() got called, and there was no guarantee that CPU0 was
the one calling machine_power_off().   BUG.

The above patch guarantees that only the single boot CPU is running
and calling machine_power_off().

Hopefully this buries the SMP-power-off bogeyman for good!

Cheers
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