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PM / Hibernate: Freeze kernel threads after preallocating memory

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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>
This commit is contained in:
Rafael J. Wysocki 2011-09-26 20:32:27 +02:00
parent 8f88893c05
commit 2aede851dd
5 changed files with 33 additions and 20 deletions
Download patch file Download diff file Expand all files Collapse all files

12
kernel/power/hibernate.c
View file

@ -334,12 +334,16 @@ int hibernation_snapshot(int platform_mode)
if (error)
goto Close;
error = dpm_prepare(PMSG_FREEZE);
if (error)
goto Complete_devices;
/* Preallocate image memory before shutting down devices. */
error = hibernate_preallocate_memory();
if (error)
goto Close;
error = freeze_kernel_threads();
if (error)
goto Close;
error = dpm_prepare(PMSG_FREEZE);
if (error)
goto Complete_devices;