[PATCH] swsusp: debugging

Add a swsusp debugging mode.  This does everything that's needed for a suspend
except for actually suspending.  So we can look in the log messages and work
out a) what code is being slow and b) which drivers are misbehaving.

(1)
# echo testproc > /sys/power/disk
# echo disk > /sys/power/state

This should turn off the non-boot CPU, freeze all processes, wait for 5
seconds and then thaw the processes and the CPU.

(2)
# echo test > /sys/power/disk
# echo disk > /sys/power/state

This should turn off the non-boot CPU, freeze all processes, shrink
memory, suspend all devices, wait for 5 seconds, resume the devices etc.

Cc: Pavel Machek <pavel@ucw.cz>
Cc: Stefan Seyfried <seife@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

4 files changed, 60 insertions, 11 deletions

diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power
index d882f8093871..dcff4d0623ad 100644
--- a/Documentation/ABI/testing/sysfs-power
+++ b/Documentation/ABI/testing/sysfs-power
@@ -21,7 +21,7 @@ Description:
                 these states.
 
 What:           /sys/power/disk
-Date:           August 2006
+Date:           September 2006
 Contact:        Rafael J. Wysocki <rjw@sisk.pl>
 Description:
                 The /sys/power/disk file controls the operating mode of the
@@ -39,6 +39,19 @@ Description:
                 'reboot' - the memory image will be saved by the kernel and
                 the system will be rebooted.
 
+                Additionally, /sys/power/disk can be used to turn on one of the
+                two testing modes of the suspend-to-disk mechanism: 'testproc'
+                or 'test'.  If the suspend-to-disk mechanism is in the
+                'testproc' mode, writing 'disk' to /sys/power/state will cause
+                the kernel to disable nonboot CPUs and freeze tasks, wait for 5
+                seconds, unfreeze tasks and enable nonboot CPUs.  If it is in
+                the 'test' mode, writing 'disk' to /sys/power/state will cause
+                the kernel to disable nonboot CPUs and freeze tasks, shrink
+                memory, suspend devices, wait for 5 seconds, resume devices,
+                unfreeze tasks and enable nonboot CPUs.  Then, we are able to
+                look in the log messages and work out, for example, which code
+                is being slow and which device drivers are misbehaving.
+
                 The suspend-to-disk method may be chosen by writing to this
                 file one of the accepted strings:
 
@@ -46,6 +59,8 @@ Description:
                 'platform'
                 'shutdown'
                 'reboot'
+                'testproc'
+                'test'
 
                 It will only change to 'firmware' or 'platform' if the system
                 supports that.
diff --git a/Documentation/power/interface.txt b/Documentation/power/interface.txt
index a66bec222b16..74311d7e0f3c 100644
--- a/Documentation/power/interface.txt
+++ b/Documentation/power/interface.txt
@@ -30,6 +30,17 @@ testing). The system will support either 'firmware' or 'platform', and
 that is known a priori. But, the user may choose 'shutdown' or
 'reboot' as alternatives. 
 
+Additionally, /sys/power/disk can be used to turn on one of the two testing
+modes of the suspend-to-disk mechanism: 'testproc' or 'test'.  If the
+suspend-to-disk mechanism is in the 'testproc' mode, writing 'disk' to
+/sys/power/state will cause the kernel to disable nonboot CPUs and freeze
+tasks, wait for 5 seconds, unfreeze tasks and enable nonboot CPUs.  If it is
+in the 'test' mode, writing 'disk' to /sys/power/state will cause the kernel
+to disable nonboot CPUs and freeze tasks, shrink memory, suspend devices, wait
+for 5 seconds, resume devices, unfreeze tasks and enable nonboot CPUs.  Then,
+we are able to look in the log messages and work out, for example, which code
+is being slow and which device drivers are misbehaving.
+
 Reading from this file will display what the mode is currently set
 to. Writing to this file will accept one of
 
@@ -37,6 +48,8 @@ to. Writing to this file will accept one of
        'platform'
        'shutdown'
        'reboot'
+       'testproc'
+       'test'
 
 It will only change to 'firmware' or 'platform' if the system supports
 it. 
diff --git a/include/linux/pm.h b/include/linux/pm.h
index 6b27e07aef19..070394e846d0 100644
--- a/include/linux/pm.h
+++ b/include/linux/pm.h
@@ -116,7 +116,9 @@ typedef int __bitwise suspend_disk_method_t;
 #define PM_DISK_PLATFORM        ((__force suspend_disk_method_t) 2)
 #define PM_DISK_SHUTDOWN        ((__force suspend_disk_method_t) 3)
 #define PM_DISK_REBOOT          ((__force suspend_disk_method_t) 4)
-#define PM_DISK_MAX             ((__force suspend_disk_method_t) 5)
+#define PM_DISK_TEST            ((__force suspend_disk_method_t) 5)
+#define PM_DISK_TESTPROC        ((__force suspend_disk_method_t) 6)
+#define PM_DISK_MAX             ((__force suspend_disk_method_t) 7)
 
 struct pm_ops {
         suspend_disk_method_t pm_disk_mode;
diff --git a/kernel/power/disk.c b/kernel/power/disk.c
index d3a158a60312..b1fb7866b0b3 100644
--- a/kernel/power/disk.c
+++ b/kernel/power/disk.c
@@ -71,7 +71,7 @@ static inline void platform_finish(void)
 
 static int prepare_processes(void)
 {
-        int error;
+        int error = 0;
 
         pm_prepare_console();
 
@@ -84,6 +84,12 @@ static int prepare_processes(void)
                 goto thaw;
         }
 
+        if (pm_disk_mode == PM_DISK_TESTPROC) {
+                printk("swsusp debug: Waiting for 5 seconds.\n");
+                mdelay(5000);
+                goto thaw;
+        }
+
         /* Free memory before shutting down devices. */
         if (!(error = swsusp_shrink_memory()))
                 return 0;
@@ -120,13 +126,21 @@ int pm_suspend_disk(void)
         if (error)
                 return error;
 
+        if (pm_disk_mode == PM_DISK_TESTPROC)
+                goto Thaw;
+
         suspend_console();
         error = device_suspend(PMSG_FREEZE);
         if (error) {
                 resume_console();
                 printk("Some devices failed to suspend\n");
-                unprepare_processes();
-                return error;
+                goto Thaw;
+        }
+
+        if (pm_disk_mode == PM_DISK_TEST) {
+                printk("swsusp debug: Waiting for 5 seconds.\n");
+                mdelay(5000);
+                goto Done;
         }
 
         pr_debug("PM: snapshotting memory.\n");
@@ -143,16 +157,17 @@ int pm_suspend_disk(void)
                         power_down(pm_disk_mode);
                 else {
                         swsusp_free();
-                        unprepare_processes();
-                        return error;
+                        goto Thaw;
                 }
-        } else
+        } else {
                 pr_debug("PM: Image restored successfully.\n");
+        }
 
         swsusp_free();
  Done:
         device_resume();
         resume_console();
+ Thaw:
         unprepare_processes();
         return error;
 }
@@ -249,6 +264,8 @@ static const char * const pm_disk_modes[] = {
         [PM_DISK_PLATFORM]      = "platform",
         [PM_DISK_SHUTDOWN]      = "shutdown",
         [PM_DISK_REBOOT]        = "reboot",
+        [PM_DISK_TEST]          = "test",
+        [PM_DISK_TESTPROC]      = "testproc",
 };
 
 /**
@@ -303,17 +320,19 @@ static ssize_t disk_store(struct subsystem * s, const char * buf, size_t n)
                 }
         }
         if (mode) {
-                if (mode == PM_DISK_SHUTDOWN || mode == PM_DISK_REBOOT)
+                if (mode == PM_DISK_SHUTDOWN || mode == PM_DISK_REBOOT ||
+                     mode == PM_DISK_TEST || mode == PM_DISK_TESTPROC) {
                         pm_disk_mode = mode;
-                else {
+                } else {
                         if (pm_ops && pm_ops->enter &&
                             (mode == pm_ops->pm_disk_mode))
                                 pm_disk_mode = mode;
                         else
                                 error = -EINVAL;
                 }
-        } else
+        } else {
                 error = -EINVAL;
+        }
 
         pr_debug("PM: suspend-to-disk mode set to '%s'\n",
                  pm_disk_modes[mode]);