[PATCH] Disable CPU hotplug during suspend

The current suspend code has to be run on one CPU, so we use the CPU
hotplug to take the non-boot CPUs offline on SMP machines.  However, we
should also make sure that these CPUs will not be enabled by someone else
after we have disabled them.

The functions disable_nonboot_cpus() and enable_nonboot_cpus() are moved to
kernel/cpu.c, because they now refer to some stuff in there that should
better be static.  Also it's better if disable_nonboot_cpus() returns an
error instead of panicking if something goes wrong, and
enable_nonboot_cpus() has no reason to panic(), because the CPUs may have
been enabled by the userland before it tries to take them online.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

5 files changed, 19 insertions, 76 deletions

diff --git a/kernel/power/Makefile b/kernel/power/Makefile
index 8d0af3d..38725f5 100644
--- a/kernel/power/Makefile
+++ b/kernel/power/Makefile
@@ -7,6 +7,4 @@ obj-y				:= main.o process.o console.o
 obj-$(CONFIG_PM_LEGACY)		+= pm.o
 obj-$(CONFIG_SOFTWARE_SUSPEND)	+= swsusp.o disk.o snapshot.o swap.o user.o
 
-obj-$(CONFIG_SUSPEND_SMP)	+= smp.o
-
 obj-$(CONFIG_MAGIC_SYSRQ)	+= poweroff.o
diff --git a/kernel/power/disk.c b/kernel/power/disk.c
index e13e740..7c7b9b6 100644
--- a/kernel/power/disk.c
+++ b/kernel/power/disk.c
@@ -18,6 +18,7 @@
 #include <linux/fs.h>
 #include <linux/mount.h>
 #include <linux/pm.h>
+#include <linux/cpu.h>
 
 #include "power.h"
 
@@ -72,7 +73,10 @@ static int prepare_processes(void)
 	int error;
 
 	pm_prepare_console();
-	disable_nonboot_cpus();
+
+	error = disable_nonboot_cpus();
+	if (error)
+		goto enable_cpus;
 
 	if (freeze_processes()) {
 		error = -EBUSY;
@@ -84,6 +88,7 @@ static int prepare_processes(void)
 		return 0;
 thaw:
 	thaw_processes();
+enable_cpus:
 	enable_nonboot_cpus();
 	pm_restore_console();
 	return error;
diff --git a/kernel/power/main.c b/kernel/power/main.c
index 6d295c7..4d40332 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -16,6 +16,7 @@
 #include <linux/init.h>
 #include <linux/pm.h>
 #include <linux/console.h>
+#include <linux/cpu.h>
 
 #include "power.h"
 
@@ -51,7 +52,7 @@ void pm_set_ops(struct pm_ops * ops)
 
 static int suspend_prepare(suspend_state_t state)
 {
-	int error = 0;
+	int error;
 	unsigned int free_pages;
 
 	if (!pm_ops || !pm_ops->enter)
@@ -59,12 +60,9 @@ static int suspend_prepare(suspend_state_t state)
 
 	pm_prepare_console();
 
-	disable_nonboot_cpus();
-
-	if (num_online_cpus() != 1) {
-		error = -EPERM;
+	error = disable_nonboot_cpus();
+	if (error)
 		goto Enable_cpu;
-	}
 
 	if (freeze_processes()) {
 		error = -EAGAIN;
diff --git a/kernel/power/smp.c b/kernel/power/smp.c
deleted file mode 100644
index 5957312..0000000
--- a/kernel/power/smp.c
+++ /dev/null
@@ -1,62 +0,0 @@
-/*
- * drivers/power/smp.c - Functions for stopping other CPUs.
- *
- * Copyright 2004 Pavel Machek <pavel@suse.cz>
- * Copyright (C) 2002-2003 Nigel Cunningham <ncunningham@clear.net.nz>
- *
- * This file is released under the GPLv2.
- */
-
-#undef DEBUG
-
-#include <linux/smp_lock.h>
-#include <linux/interrupt.h>
-#include <linux/suspend.h>
-#include <linux/module.h>
-#include <linux/cpu.h>
-#include <asm/atomic.h>
-#include <asm/tlbflush.h>
-
-/* This is protected by pm_sem semaphore */
-static cpumask_t frozen_cpus;
-
-void disable_nonboot_cpus(void)
-{
-	int cpu, error;
-
-	error = 0;
-	cpus_clear(frozen_cpus);
-	printk("Freezing cpus ...\n");
-	for_each_online_cpu(cpu) {
-		if (cpu == 0)
-			continue;
-		error = cpu_down(cpu);
-		if (!error) {
-			cpu_set(cpu, frozen_cpus);
-			printk("CPU%d is down\n", cpu);
-			continue;
-		}
-		printk("Error taking cpu %d down: %d\n", cpu, error);
-	}
-	BUG_ON(raw_smp_processor_id() != 0);
-	if (error)
-		panic("cpus not sleeping");
-}
-
-void enable_nonboot_cpus(void)
-{
-	int cpu, error;
-
-	printk("Thawing cpus ...\n");
-	for_each_cpu_mask(cpu, frozen_cpus) {
-		error = cpu_up(cpu);
-		if (!error) {
-			printk("CPU%d is up\n", cpu);
-			continue;
-		}
-		printk("Error taking cpu %d up: %d\n", cpu, error);
-		panic("Not enough cpus");
-	}
-	cpus_clear(frozen_cpus);
-}
-
diff --git a/kernel/power/user.c b/kernel/power/user.c
index 3f1539f..0ef5e4b 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -19,6 +19,7 @@
 #include <linux/swapops.h>
 #include <linux/pm.h>
 #include <linux/fs.h>
+#include <linux/cpu.h>
 
 #include <asm/uaccess.h>
 
@@ -139,12 +140,15 @@ static int snapshot_ioctl(struct inode *inode, struct file *filp,
 		if (data->frozen)
 			break;
 		down(&pm_sem);
-		disable_nonboot_cpus();
-		if (freeze_processes()) {
-			thaw_processes();
-			enable_nonboot_cpus();
-			error = -EBUSY;
+		error = disable_nonboot_cpus();
+		if (!error) {
+			error = freeze_processes();
+			if (error) {
+				thaw_processes();
+				error = -EBUSY;
+			}
 		}
+		enable_nonboot_cpus();
 		up(&pm_sem);
 		if (!error)
 			data->frozen = 1;