powerpc: Put the gpr save/restore functions in their own section

[karo-tx-linux.git] / Documentation / power / freezing-of-tasks.txt

diff --git a/Documentation/power/freezing-of-tasks.txt b/Documentation/power/freezing-of-tasks.txt
index ec715cd78fbb7028bde53c0664a513701b162858..6ec291ea1c78c64e4e1ec35ad614336859ab4c31 100644 (file)
--- a/Documentation/power/freezing-of-tasks.txt
+++ b/Documentation/power/freezing-of-tasks.txt
@@ -9,7 +9,7 @@ architectures).
 
 II. How does it work?
 
 
 II. How does it work?
 

-There are four per-task flags used for that, PF_NOFREEZE, PF_FROZEN, TIF_FREEZE
+There are three per-task flags used for that, PF_NOFREEZE, PF_FROZEN

 and PF_FREEZER_SKIP (the last one is auxiliary).  The tasks that have
 PF_NOFREEZE unset (all user space processes and some kernel threads) are
 regarded as 'freezable' and treated in a special way before the system enters a
 and PF_FREEZER_SKIP (the last one is auxiliary).  The tasks that have
 PF_NOFREEZE unset (all user space processes and some kernel threads) are
 regarded as 'freezable' and treated in a special way before the system enters a


@@ -17,30 +17,31 @@ suspend state as well as before a hibernation image is created (in what follows
 we only consider hibernation, but the description also applies to suspend).
 
 Namely, as the first step of the hibernation procedure the function
 we only consider hibernation, but the description also applies to suspend).
 
 Namely, as the first step of the hibernation procedure the function

-freeze_processes() (defined in kernel/power/process.c) is called.  It executes
-try_to_freeze_tasks() that sets TIF_FREEZE for all of the freezable tasks and
-either wakes them up, if they are kernel threads, or sends fake signals to them,
-if they are user space processes.  A task that has TIF_FREEZE set, should react
-to it by calling the function called __refrigerator() (defined in
-kernel/freezer.c), which sets the task's PF_FROZEN flag, changes its state
-to TASK_UNINTERRUPTIBLE and makes it loop until PF_FROZEN is cleared for it.
-Then, we say that the task is 'frozen' and therefore the set of functions
-handling this mechanism is referred to as 'the freezer' (these functions are
-defined in kernel/power/process.c, kernel/freezer.c & include/linux/freezer.h).
-User space processes are generally frozen before kernel threads.
+freeze_processes() (defined in kernel/power/process.c) is called.  A system-wide
+variable system_freezing_cnt (as opposed to a per-task flag) is used to indicate
+whether the system is to undergo a freezing operation. And freeze_processes()
+sets this variable.  After this, it executes try_to_freeze_tasks() that sends a
+fake signal to all user space processes, and wakes up all the kernel threads.
+All freezable tasks must react to that by calling try_to_freeze(), which
+results in a call to __refrigerator() (defined in kernel/freezer.c), which sets
+the task's PF_FROZEN flag, changes its state to TASK_UNINTERRUPTIBLE and makes
+it loop until PF_FROZEN is cleared for it. Then, we say that the task is
+'frozen' and therefore the set of functions handling this mechanism is referred
+to as 'the freezer' (these functions are defined in kernel/power/process.c,
+kernel/freezer.c & include/linux/freezer.h). User space processes are generally
+frozen before kernel threads.

 
 __refrigerator() must not be called directly.  Instead, use the
 try_to_freeze() function (defined in include/linux/freezer.h), that checks
 
 __refrigerator() must not be called directly.  Instead, use the
 try_to_freeze() function (defined in include/linux/freezer.h), that checks

-the task's TIF_FREEZE flag and makes the task enter __refrigerator() if the
-flag is set.
+if the task is to be frozen and makes the task enter __refrigerator().

 
 For user space processes try_to_freeze() is called automatically from the
 signal-handling code, but the freezable kernel threads need to call it
 explicitly in suitable places or use the wait_event_freezable() or
 wait_event_freezable_timeout() macros (defined in include/linux/freezer.h)
 
 For user space processes try_to_freeze() is called automatically from the
 signal-handling code, but the freezable kernel threads need to call it
 explicitly in suitable places or use the wait_event_freezable() or
 wait_event_freezable_timeout() macros (defined in include/linux/freezer.h)

-that combine interruptible sleep with checking if TIF_FREEZE is set and calling
-try_to_freeze().  The main loop of a freezable kernel thread may look like the
-following one:
+that combine interruptible sleep with checking if the task is to be frozen and
+calling try_to_freeze().  The main loop of a freezable kernel thread may look
+like the following one:

 
        set_freezable();
        do {
 
        set_freezable();
        do {


@@ -53,7 +54,7 @@ following one:
 (from drivers/usb/core/hub.c::hub_thread()).
 
 If a freezable kernel thread fails to call try_to_freeze() after the freezer has
 (from drivers/usb/core/hub.c::hub_thread()).
 
 If a freezable kernel thread fails to call try_to_freeze() after the freezer has

-set TIF_FREEZE for it, the freezing of tasks will fail and the entire
+initiated a freezing operation, the freezing of tasks will fail and the entire

 hibernation operation will be cancelled.  For this reason, freezable kernel
 threads must call try_to_freeze() somewhere or use one of the
 wait_event_freezable() and wait_event_freezable_timeout() macros.
 hibernation operation will be cancelled.  For this reason, freezable kernel
 threads must call try_to_freeze() somewhere or use one of the
 wait_event_freezable() and wait_event_freezable_timeout() macros.