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| author | Rafael J. Wysocki <rjw@sisk.pl> | 2006-09-25 23:32:58 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-09-26 08:49:04 -0700 |
| commit | c5c6ba4e08ab9c9e390a0f3a7d9a5c332f5cc6ef (patch) | |
| tree | 4e13a9eebd8f3901dcc187c585369ef843d1e1a7 /Documentation/power | |
| parent | 7d145aa3abf4d96c91f37c012facd5cfbb9010d1 (diff) | |
| download | lwn-c5c6ba4e08ab9c9e390a0f3a7d9a5c332f5cc6ef.tar.gz lwn-c5c6ba4e08ab9c9e390a0f3a7d9a5c332f5cc6ef.zip | |
[PATCH] PM: Add pm_trace switch
Add the pm_trace attribute in /sys/power which has to be explicitly set to
one to really enable the "PM tracing" code compiled in when CONFIG_PM_TRACE
is set (which modifies the machine's CMOS clock in unpredictable ways).
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>
Diffstat (limited to 'Documentation/power')
| -rw-r--r-- | Documentation/power/interface.txt | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/Documentation/power/interface.txt b/Documentation/power/interface.txt index 4117802af0f8..a66bec222b16 100644 --- a/Documentation/power/interface.txt +++ b/Documentation/power/interface.txt @@ -52,3 +52,18 @@ suspend image will be as small as possible. Reading from this file will display the current image size limit, which is set to 500 MB by default. + +/sys/power/pm_trace controls the code which saves the last PM event point in +the RTC across reboots, so that you can debug a machine that just hangs +during suspend (or more commonly, during resume). Namely, the RTC is only +used to save the last PM event point if this file contains '1'. Initially it +contains '0' which may be changed to '1' by writing a string representing a +nonzero integer into it. + +To use this debugging feature you should attempt to suspend the machine, then +reboot it and run + + dmesg -s 1000000 | grep 'hash matches' + +CAUTION: Using it will cause your machine's real-time (CMOS) clock to be +set to a random invalid time after a resume. |