[PATCH] i386/x86-64: Don't IPI to offline cpus on shutdown
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>
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@ -12,6 +12,7 @@
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#include <linux/efi.h>
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#include <linux/dmi.h>
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#include <linux/ctype.h>
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#include <linux/pm.h>
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#include <asm/uaccess.h>
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#include <asm/apic.h>
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#include <asm/desc.h>
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@ -355,10 +356,10 @@ void machine_halt(void)
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void machine_power_off(void)
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{
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machine_shutdown();
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if (pm_power_off)
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if (pm_power_off) {
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machine_shutdown();
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pm_power_off();
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}
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}
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@ -6,6 +6,7 @@
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#include <linux/kernel.h>
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#include <linux/ctype.h>
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#include <linux/string.h>
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#include <linux/pm.h>
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#include <asm/io.h>
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#include <asm/kdebug.h>
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#include <asm/delay.h>
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@ -154,10 +155,11 @@ void machine_halt(void)
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void machine_power_off(void)
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{
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if (!reboot_force) {
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machine_shutdown();
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}
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if (pm_power_off)
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if (pm_power_off) {
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if (!reboot_force) {
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machine_shutdown();
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}
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pm_power_off();
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}
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}
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