freezer: set PF_SUSPEND_TASK flag on tasks that call freeze_processes
authorColin Cross <ccross@android.com>
Thu, 25 Jul 2013 00:41:33 +0000 (17:41 -0700)
committerDan Willemsen <dwillemsen@nvidia.com>
Sat, 14 Sep 2013 20:40:05 +0000 (13:40 -0700)
commitee50ab880b3481a6fe982c67b531c4997fc5aa95
tree0487a685166e5ea33a959d7f3f7fd86f463fed3c
parentea763310fd51b997f771b3a74d27b0039c638df5
freezer: set PF_SUSPEND_TASK flag on tasks that call freeze_processes

Calling freeze_processes sets a global flag that will cause any
process that calls try_to_freeze to enter the refrigerator.  It
skips sending a signal to the current task, but if the current
task ever hits try_to_freeze, all threads will be frozen and the
system will deadlock.

Set a new flag, PF_SUSPEND_TASK, on the task that calls
freeze_processes.  The flag notifies the freezer that the thread
is involved in suspend and should not be frozen.  Also add a
WARN_ON in thaw_processes if the caller does not have the
PF_SUSPEND_TASK flag set to catch if a different task calls
thaw_processes than the one that called freeze_processes, leaving
a task with PF_SUSPEND_TASK permanently set on it.

Threads that spawn off a task with PF_SUSPEND_TASK set (which
swsusp does) will also have PF_SUSPEND_TASK set, preventing them
from freezing while they are helping with suspend, but they need
to be dead by the time suspend is triggered, otherwise they may
run when userspace is expected to be frozen.  Add a WARN_ON in
thaw_processes if more than one thread has the PF_SUSPEND_TASK
flag set.

Reported-and-tested-by: Michael Leun <lkml20130126@newton.leun.net>
Signed-off-by: Colin Cross <ccross@android.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
(cherry picked from commit 2b44c4db2e2f1765d35163a861d301038e0c8a75)
Change-Id: I12e00d2ba61db827c07b8f4ef48e88a722f02d71
Reviewed-on: http://git-master/r/259126
Reviewed-by: Prashant Gaikwad <pgaikwad@nvidia.com>
Tested-by: Prashant Gaikwad <pgaikwad@nvidia.com>
Reviewed-by: Bharat Nihalani <bnihalani@nvidia.com>
include/linux/sched.h
kernel/freezer.c
kernel/power/process.c