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authorRafael J. Wysocki <rjw@sisk.pl>2011-09-26 20:32:27 +0200
committerRafael J. Wysocki <rjw@sisk.pl>2011-10-16 23:28:52 +0200
commit2aede851ddf08666f68ffc17be446420e9d2a056 (patch)
treef63a0477c9fe618cd374065bac4cb5f172aaf7db /Documentation/power
parent8f88893c05f2f677f18f2ce5591b4bed5d4a7535 (diff)
PM / Hibernate: Freeze kernel threads after preallocating memory
There is a problem with the current ordering of hibernate code which leads to deadlocks in some filesystems' memory shrinkers. Namely, some filesystems use freezable kernel threads that are inactive when the hibernate memory preallocation is carried out. Those same filesystems use memory shrinkers that may be triggered by the hibernate memory preallocation. If those memory shrinkers wait for the frozen kernel threads, the hibernate process deadlocks (this happens with XFS, for one example). Apparently, it is not technically viable to redesign the filesystems in question to avoid the situation described above, so the only possible solution of this issue is to defer the freezing of kernel threads until the hibernate memory preallocation is done, which is implemented by this change. Unfortunately, this requires the memory preallocation to be done before the "prepare" stage of device freeze, so after this change the only way drivers can allocate additional memory for their freeze routines in a clean way is to use PM notifiers. Reported-by: Christoph <cr2005@u-club.de> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Diffstat (limited to 'Documentation/power')
-rw-r--r--Documentation/power/devices.txt4
1 files changed, 0 insertions, 4 deletions
diff --git a/Documentation/power/devices.txt b/Documentation/power/devices.txt
index 29b7a9817f5..646a89e0c07 100644
--- a/Documentation/power/devices.txt
+++ b/Documentation/power/devices.txt
@@ -281,10 +281,6 @@ When the system goes into the standby or memory sleep state, the phases are:
time.) Unlike the other suspend-related phases, during the prepare
phase the device tree is traversed top-down.
- In addition to that, if device drivers need to allocate additional
- memory to be able to hadle device suspend correctly, that should be
- done in the prepare phase.
-
After the prepare callback method returns, no new children may be
registered below the device. The method may also prepare the device or
driver in some way for the upcoming system power transition (for