Documentation/power/freezing-of-tasks.rst

11 kernel threads are controlled during hibernation or system-wide suspend (on some
17 There are three per-task flags used for that, PF_NOFREEZE, PF_FROZEN
20 regarded as 'freezable' and treated in a special way before the system enters a
25 freeze_processes() (defined in kernel/power/process.c) is called.  A system-wide
26 variable system_freezing_cnt (as opposed to a per-task flag) is used to indicate
27 whether the system is to undergo a freezing operation. And freeze_processes()
44 signal-handling code, but the freezable kernel threads need to call it
67 After the system memory state has been restored from a hibernation image and
74 -------------------------------------------------------------------------
77   - freezes only userspace tasks
80   - freezes all tasks (including kernel threads) because we can't freeze
84   - thaws only kernel threads; this is particularly useful if we need to do
89   - thaws all tasks (including kernel threads) because we can't thaw userspace
111    filesystem-related information that must be consistent with the state of the
112    on-disk data and metadata after the system memory state has been restored
115    tasks that might cause the on-disk filesystems' data and metadata to be
117    system is finally powered off. The majority of these are user space
162    space processes should not notice that such a system-wide operation has
189    (https://lists.linux-foundation.org/pipermail/linux-pm/2007-May/012309.html).
211 Documentation/driver-api/pm/notifiers.rst.
219 piece of code from system-wide sleep such as suspend/hibernation is not
222 CPU-Hotplug code (kernel/cpu.c) for an example.