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    Subject[patch 10/39] [PATCH] i386/x86-64: Dont IPI to offline cpus on shutdown
    -stable review patch.  If anyone has any objections, please let us know.
    ------------------

    So why are we calling smp_send_stop from machine_halt?

    We don't.

    Looking more closely at the bug report the problem here
    is that halt -p is called which triggers not a halt but
    an attempt to power off.

    machine_power_off calls machine_shutdown which calls smp_send_stop.

    If pm_power_off is set we should never make it out machine_power_off
    to the call of do_exit. So pm_power_off must not be set in this case.
    When pm_power_off is not set we expect machine_power_off to devolve
    into machine_halt.

    So how do we fix this?

    Playing too much with smp_send_stop is dangerous because it
    must also be safe to be called from panic.

    It looks like the obviously correct fix is to only call
    machine_shutdown when pm_power_off is defined. Doing
    that will make Andi's assumption about not scheduling
    true and generally simplify what must be supported.

    This turns machine_power_off into a noop like machine_halt
    when pm_power_off is not defined.

    If the expected behavior is that sys_reboot(LINUX_REBOOT_CMD_POWER_OFF)
    becomes sys_reboot(LINUX_REBOOT_CMD_HALT) if pm_power_off is NULL
    this is not quite a comprehensive fix as we pass a different parameter
    to the reboot notifier and we set system_state to a different value
    before calling device_shutdown().

    Unfortunately any fix more comprehensive I can think of is not
    obviously correct. The core problem is that there is no architecture
    independent way to detect if machine_power will become a noop, without
    calling it.

    Signed-off-by: Andi Kleen <ak@suse.de>
    Signed-off-by: Linus Torvalds <torvalds@osdl.org>
    Signed-off-by: Chris Wright <chrisw@sous-sol.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
    ---

    arch/i386/kernel/reboot.c | 7 ++++---
    arch/x86_64/kernel/reboot.c | 10 ++++++----
    2 files changed, 10 insertions(+), 7 deletions(-)

    diff --git a/arch/i386/kernel/reboot.c b/arch/i386/kernel/reboot.c
    index 2fa5803..d207242 100644
    --- linux-2.6.15.4.orig/arch/i386/kernel/reboot.c
    +++ linux-2.6.15.4/arch/i386/kernel/reboot.c
    @@ -12,6 +12,7 @@
    #include <linux/efi.h>
    #include <linux/dmi.h>
    #include <linux/ctype.h>
    +#include <linux/pm.h>
    #include <asm/uaccess.h>
    #include <asm/apic.h>
    #include <asm/desc.h>
    @@ -355,10 +356,10 @@ void machine_halt(void)

    void machine_power_off(void)
    {
    - machine_shutdown();
    -
    - if (pm_power_off)
    + if (pm_power_off) {
    + machine_shutdown();
    pm_power_off();
    + }
    }


    --- linux-2.6.15.4.orig/arch/x86_64/kernel/reboot.c
    +++ linux-2.6.15.4/arch/x86_64/kernel/reboot.c
    @@ -6,6 +6,7 @@
    #include <linux/kernel.h>
    #include <linux/ctype.h>
    #include <linux/string.h>
    +#include <linux/pm.h>
    #include <asm/io.h>
    #include <asm/kdebug.h>
    #include <asm/delay.h>
    @@ -154,10 +155,11 @@ void machine_halt(void)

    void machine_power_off(void)
    {
    - if (!reboot_force) {
    - machine_shutdown();
    - }
    - if (pm_power_off)
    + if (pm_power_off) {
    + if (!reboot_force) {
    + machine_shutdown();
    + }
    pm_power_off();
    + }
    }

    --
    -
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