[PATCH] Don't attempt to power off if power off is not implemented

The problem. It is expected that /sbin/halt -p works exactly like /sbin/halt, when the kernel does not implement power off functionality. The kernel can do a lot of work in the reboot notifiers and in device_shutdown before we even get to machine_power_off. Some of that shutdown is not safe if you are leaving the power on, and it definitely gets in the way of using sysrq or pressing ctrl-alt-del. Since the shutdown happens in generic code there is no way to fix this in architecture specific code :( Some machines are kernel oopsing today because of this. The simple solution is to turn LINUX_REBOOT_CMD_POWER_OFF into LINUX_REBOOT_CMD_HALT if power_off functionality is not implemented. This has the unfortunate side effect of disabling the power off functionality on architectures that leave pm_power_off to null and still implement something in machine_power_off. And it will break the build on some architectures that don't have a pm_power_off variable at all. On both counts I say tough. For architectures like alpha that don't implement the pm_power_off variable pm_power_off is declared in linux/pm.h and it is a generic part of our power management code, and all architectures should implement it. For architectures like parisc that have a default power off method in machine_power_off if pm_power_off is not implemented or fails. It is easy enough to set the pm_power_off variable. And nothing bad happens there, the machines just stop powering off. The current semantics are impossible without a flag at the top level so we can avoid the problem code if a power off is not implemented. pm_power_off is as good a flag as any with the bonus that it works without modification on at least x86, x86_64, powerpc, and ppc today. Andrew can you pick this up and put this in the mm tree. Kernels that don't compile or don't power off seem saner than kernels that oops or panic. Until we get the arch specific patches for the problem architectures this probably isn't smart to push into the stable kernel. Unfortunately I don't have the time at the moment to walk through every architecture and make them work. And even if I did I couldn't test it :( From: Hirokazu Takata <takata@linux-m32r.org> Add pm_power_off() for build fix of arch/m32r/kernel/process.c. From: Miklos Szeredi <miklos@szeredi.hu> UML build fix Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Hayato Fujiwara <fujiwara@linux-m32r.org> Signed-off-by: Hirokazu Takata <takata@linux-m32r.org> Signed-off-by: Miklos Szeredi <miklos@szeredi.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] Don't attempt to power off if power off is not implemented
The problem. It is expected that /sbin/halt -p works exactly like /sbin/halt, when the kernel does not implement power off functionality. The kernel can do a lot of work in the reboot notifiers and in device_shutdown before we even get to machine_power_off. Some of that shutdown is not safe if you are leaving the power on, and it definitely gets in the way of using sysrq or pressing ctrl-alt-del. Since the shutdown happens in generic code there is no way to fix this in architecture specific code :( Some machines are kernel oopsing today because of this. The simple solution is to turn LINUX_REBOOT_CMD_POWER_OFF into LINUX_REBOOT_CMD_HALT if power_off functionality is not implemented. This has the unfortunate side effect of disabling the power off functionality on architectures that leave pm_power_off to null and still implement something in machine_power_off. And it will break the build on some architectures that don't have a pm_power_off variable at all. On both counts I say tough. For architectures like alpha that don't implement the pm_power_off variable pm_power_off is declared in linux/pm.h and it is a generic part of our power management code, and all architectures should implement it. For architectures like parisc that have a default power off method in machine_power_off if pm_power_off is not implemented or fails. It is easy enough to set the pm_power_off variable. And nothing bad happens there, the machines just stop powering off. The current semantics are impossible without a flag at the top level so we can avoid the problem code if a power off is not implemented. pm_power_off is as good a flag as any with the bonus that it works without modification on at least x86, x86_64, powerpc, and ppc today. Andrew can you pick this up and put this in the mm tree. Kernels that don't compile or don't power off seem saner than kernels that oops or panic. Until we get the arch specific patches for the problem architectures this probably isn't smart to push into the stable kernel. Unfortunately I don't have the time at the moment to walk through every architecture and make them work. And even if I did I couldn't test it :( From: Hirokazu Takata <takata@linux-m32r.org> Add pm_power_off() for build fix of arch/m32r/kernel/process.c. From: Miklos Szeredi <miklos@szeredi.hu> UML build fix Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Hayato Fujiwara <fujiwara@linux-m32r.org> Signed-off-by: Hirokazu Takata <takata@linux-m32r.org> Signed-off-by: Miklos Szeredi <miklos@szeredi.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Eric W. Biederman · Linus Torvalds
1 parent 87ba81dba4
Showing 4 changed files with 17 additions and 0 deletions Side-by-side Diff
arch/alpha/kernel/process.c
arch/m32r/kernel/process.c
arch/um/kernel/reboot.c
kernel/sys.c
@@ -43,6 +43,11 @@
 #include "proto.h"
 #include "pci_impl.h"
  
+/*
+ * Power off function, if any
+ */
+void (*pm_power_off)(void) = machine_power_off;
+
 void
 cpu_idle(void)
 {
@@ -50,6 +50,10 @@
  * Powermanagement idle function, if any..
  */
 void (*pm_idle)(void) = NULL;
+EXPORT_SYMBOL(pm_idle);
+
+void (*pm_power_off)(void) = NULL;
+EXPORT_SYMBOL(pm_power_off);
  
 void disable_hlt(void)
 {
@@ -12,6 +12,8 @@
 #include "mode.h"
 #include "choose-mode.h"
  
+void (*pm_power_off)(void);
+
 #ifdef CONFIG_SMP
 static void kill_idlers(int me)
 {
@@ -489,6 +489,12 @@
 	                magic2 != LINUX_REBOOT_MAGIC2C))
 		return -EINVAL;
  
+	/* Instead of trying to make the power_off code look like
+	 * halt when pm_power_off is not set do it the easy way.
+	 */
+	if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
+		cmd = LINUX_REBOOT_CMD_HALT;
+
 	lock_kernel();
 	switch (cmd) {
 	case LINUX_REBOOT_CMD_RESTART:
...	...	@@ -43,6 +43,11 @@
43	43	#include "proto.h"
44	44	#include "pci_impl.h"
45	45
	46	+/*
	47	+ * Power off function, if any
	48	+ */
	49	+void (*pm_power_off)(void) = machine_power_off;
	50	+
46	51	void
47	52	cpu_idle(void)
48	53	{
...	...	@@ -50,6 +50,10 @@
50	50	* Powermanagement idle function, if any..
51	51	*/
52	52	void (*pm_idle)(void) = NULL;
	53	+EXPORT_SYMBOL(pm_idle);
	54	+
	55	+void (*pm_power_off)(void) = NULL;
	56	+EXPORT_SYMBOL(pm_power_off);
53	57
54	58	void disable_hlt(void)
55	59	{
...	...	@@ -12,6 +12,8 @@
12	12	#include "mode.h"
13	13	#include "choose-mode.h"
14	14
	15	+void (*pm_power_off)(void);
	16	+
15	17	#ifdef CONFIG_SMP
16	18	static void kill_idlers(int me)
17	19	{
...	...	@@ -489,6 +489,12 @@
489	489	magic2 != LINUX_REBOOT_MAGIC2C))
490	490	return -EINVAL;
491	491
	492	+ /* Instead of trying to make the power_off code look like
	493	+ * halt when pm_power_off is not set do it the easy way.
	494	+ */
	495	+ if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
	496	+ cmd = LINUX_REBOOT_CMD_HALT;
	497	+
492	498	lock_kernel();
493	499	switch (cmd) {
494	500	case LINUX_REBOOT_CMD_RESTART: