[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>

1 files changed, 16 insertions, 1 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.