pm: rework disabling of user mode helpers during suspend/hibernation

We currently use a PM notifier to disable user mode helpers before suspend
and hibernation and to re-enable them during resume.  However, this is not
an ideal solution, because if any drivers want to upload firmware into
memory before suspend, they have to use a PM notifier for this purpose and
there is no guarantee that the ordering of PM notifiers will be as
expected (ie.  the notifier that disables user mode helpers has to be run
after the driver's notifier used for uploading the firmware).

For this reason, it seems better to move the disabling and enabling of
user mode helpers to separate functions that will be called by the PM core
as necessary.

[akpm@linux-foundation.org: remove unneeded ifdefs]
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/power/disk.c

diff --git a/kernel/power/disk.c b/kernel/power/disk.c
index bbd85c6..331f983 100644
--- a/kernel/power/disk.c
+++ b/kernel/power/disk.c
@@ -14,6 +14,7 @@
 #include <linux/reboot.h>
 #include <linux/string.h>
 #include <linux/device.h>
+#include <linux/kmod.h>
 #include <linux/delay.h>
 #include <linux/fs.h>
 #include <linux/mount.h>
@@ -520,6 +521,10 @@
 	if (error)
 		goto Exit;
 
+	error = usermodehelper_disable();
+	if (error)
+		goto Exit;
+
 	/* Allocate memory management structures */
 	error = create_basic_memory_bitmaps();
 	if (error)
@@ -558,6 +563,7 @@
 	thaw_processes();
  Finish:
 	free_basic_memory_bitmaps();
+	usermodehelper_enable();
  Exit:
 	pm_notifier_call_chain(PM_POST_HIBERNATION);
 	pm_restore_console();
@@ -634,6 +640,10 @@
 	if (error)
 		goto Finish;
 
+	error = usermodehelper_disable();
+	if (error)
+		goto Finish;
+
 	error = create_basic_memory_bitmaps();
 	if (error)
 		goto Finish;
@@ -656,6 +666,7 @@
 	thaw_processes();
  Done:
 	free_basic_memory_bitmaps();
+	usermodehelper_enable();
  Finish:
 	pm_notifier_call_chain(PM_POST_RESTORE);
 	pm_restore_console();

kernel/power/main.c

diff --git a/kernel/power/main.c b/kernel/power/main.c
index 540b16b6..19122cf 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -14,6 +14,7 @@
 #include <linux/string.h>
 #include <linux/delay.h>
 #include <linux/errno.h>
+#include <linux/kmod.h>
 #include <linux/init.h>
 #include <linux/console.h>
 #include <linux/cpu.h>
@@ -237,6 +238,10 @@
 	if (error)
 		goto Finish;
 
+	error = usermodehelper_disable();
+	if (error)
+		goto Finish;
+
 	if (suspend_freeze_processes()) {
 		error = -EAGAIN;
 		goto Thaw;
@@ -256,6 +261,7 @@
 
  Thaw:
 	suspend_thaw_processes();
+	usermodehelper_enable();
  Finish:
 	pm_notifier_call_chain(PM_POST_SUSPEND);
 	pm_restore_console();
@@ -376,6 +382,7 @@
 static void suspend_finish(void)
 {
 	suspend_thaw_processes();
+	usermodehelper_enable();
 	pm_notifier_call_chain(PM_POST_SUSPEND);
 	pm_restore_console();
 }

kernel/power/user.c

diff --git a/kernel/power/user.c b/kernel/power/user.c
index a6332a3..005b93d 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -212,13 +212,20 @@
 	case SNAPSHOT_FREEZE:
 		if (data->frozen)
 			break;
+
 		printk("Syncing filesystems ... ");
 		sys_sync();
 		printk("done.\n");
 
-		error = freeze_processes();
+		error = usermodehelper_disable();
 		if (error)
+			break;
+
+		error = freeze_processes();
+		if (error) {
 			thaw_processes();
+			usermodehelper_enable();
+		}
 		if (!error)
 			data->frozen = 1;
 		break;
@@ -227,6 +234,7 @@
 		if (!data->frozen || data->ready)
 			break;
 		thaw_processes();
+		usermodehelper_enable();
 		data->frozen = 0;
 		break;