[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>

1 files changed, 9 insertions, 5 deletions

diff --git a/kernel/power/user.c b/kernel/power/user.c
index 3f1539fbe48a..0ef5e4ba39e5 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;