path: root/Documentation/cpu-hotplug.txt
diff options
authorRafael J. Wysocki <rjw@sisk.pl>2007-05-09 02:35:10 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-09 12:30:56 -0700
commit8bb7844286fb8c9fce6f65d8288aeb09d03a5e0d (patch)
treef4e305edaedbde05774bb1e4acd89a9475661d2e /Documentation/cpu-hotplug.txt
parentf37bc2712b54ec641e0c0c8634f1a4b61d9956c0 (diff)
Add suspend-related notifications for CPU hotplug
Since nonboot CPUs are now disabled after tasks and devices have been frozen and the CPU hotplug infrastructure is used for this purpose, we need special CPU hotplug notifications that will help the CPU-hotplug-aware subsystems distinguish normal CPU hotplug events from CPU hotplug events related to a system-wide suspend or resume operation in progress. This patch introduces such notifications and causes them to be used during suspend and resume transitions. It also changes all of the CPU-hotplug-aware subsystems to take these notifications into consideration (for now they are handled in the same way as the corresponding "normal" ones). [oleg@tv-sign.ru: cleanups] Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Cc: Gautham R Shenoy <ego@in.ibm.com> Cc: Pavel Machek <pavel@ucw.cz> Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/cpu-hotplug.txt')
1 files changed, 7 insertions, 2 deletions
diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt
index cc60d29b954c..b6d24c22274b 100644
--- a/Documentation/cpu-hotplug.txt
+++ b/Documentation/cpu-hotplug.txt
@@ -217,14 +217,17 @@ Q: What happens when a CPU is being logically offlined?
A: The following happen, listed in no particular order :-)
- A notification is sent to in-kernel registered modules by sending an event
+ CPU_DOWN_PREPARE or CPU_DOWN_PREPARE_FROZEN, depending on whether or not the
+ CPU is being offlined while tasks are frozen due to a suspend operation in
+ progress
- All process is migrated away from this outgoing CPU to a new CPU
- All interrupts targeted to this CPU is migrated to a new CPU
- timers/bottom half/task lets are also migrated to a new CPU
- Once all services are migrated, kernel calls an arch specific routine
__cpu_disable() to perform arch specific cleanup.
- Once this is successful, an event for successful cleanup is sent by an event
+ CPU_DEAD (or CPU_DEAD_FROZEN if tasks are frozen due to a suspend while the
+ CPU is being offlined).
"It is expected that each service cleans up when the CPU_DOWN_PREPARE
notifier is called, when CPU_DEAD is called its expected there is nothing
@@ -242,9 +245,11 @@ A: This is what you would need in your kernel code to receive notifications.
switch (action) {
case CPU_DEAD:

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