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-rw-r--r--Documentation/power/freezing-of-tasks.txt21
1 files changed, 21 insertions, 0 deletions
diff --git a/Documentation/power/freezing-of-tasks.txt b/Documentation/power/freezing-of-tasks.txt
index ebd7490ef1df..ec715cd78fbb 100644
--- a/Documentation/power/freezing-of-tasks.txt
+++ b/Documentation/power/freezing-of-tasks.txt
@@ -63,6 +63,27 @@ devices have been reinitialized, the function thaw_processes() is called in
order to clear the PF_FROZEN flag for each frozen task. Then, the tasks that
have been frozen leave __refrigerator() and continue running.
+
+Rationale behind the functions dealing with freezing and thawing of tasks:
+-------------------------------------------------------------------------
+
+freeze_processes():
+ - freezes only userspace tasks
+
+freeze_kernel_threads():
+ - freezes all tasks (including kernel threads) because we can't freeze
+ kernel threads without freezing userspace tasks
+
+thaw_kernel_threads():
+ - thaws only kernel threads; this is particularly useful if we need to do
+ anything special in between thawing of kernel threads and thawing of
+ userspace tasks, or if we want to postpone the thawing of userspace tasks
+
+thaw_processes():
+ - thaws all tasks (including kernel threads) because we can't thaw userspace
+ tasks without thawing kernel threads
+
+
III. Which kernel threads are freezable?
Kernel threads are not freezable by default. However, a kernel thread may clear