From: Heinrich Schuchardt Date: Sat, 21 Feb 2015 23:18:49 +0000 (+0100) Subject: Doc/memory-hotplug.txt: corrections and callback function prototype X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=433b89cfb40f6bb6e6b6c899d06e40dd4f2ed100;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git Doc/memory-hotplug.txt: corrections and callback function prototype Documentation/memory-hotplug.txt describes that a callback function can be added to the notification chain by calling hotplug_memory_notifier(). The function prototype of the callback function is mssing. This missing information is added by the patch. The description of the arguments of the callback function is reworked. The constants for the event types are corrected. The possible return values are explained. Signed-off-by: Heinrich Schuchardt Signed-off-by: Jonathan Corbet --- diff --git a/Documentation/memory-hotplug.txt b/Documentation/memory-hotplug.txt index ea03abfc97e9..c5a064508a3c 100644 --- a/Documentation/memory-hotplug.txt +++ b/Documentation/memory-hotplug.txt @@ -359,38 +359,51 @@ Need more implementation yet.... -------------------------------- 8. Memory hotplug event notifier -------------------------------- -Memory hotplug has event notifier. There are 6 types of notification. +Hotplugging events are sent to a notification queue. -MEMORY_GOING_ONLINE +There are six types of notification defined in include/linux/memory.h: + +MEM_GOING_ONLINE Generated before new memory becomes available in order to be able to prepare subsystems to handle memory. The page allocator is still unable to allocate from the new memory. -MEMORY_CANCEL_ONLINE +MEM_CANCEL_ONLINE Generated if MEMORY_GOING_ONLINE fails. -MEMORY_ONLINE +MEM_ONLINE Generated when memory has successfully brought online. The callback may allocate pages from the new memory. -MEMORY_GOING_OFFLINE +MEM_GOING_OFFLINE Generated to begin the process of offlining memory. Allocations are no longer possible from the memory but some of the memory to be offlined is still in use. The callback can be used to free memory known to a subsystem from the indicated memory block. -MEMORY_CANCEL_OFFLINE +MEM_CANCEL_OFFLINE Generated if MEMORY_GOING_OFFLINE fails. Memory is available again from the memory block that we attempted to offline. -MEMORY_OFFLINE +MEM_OFFLINE Generated after offlining memory is complete. -A callback routine can be registered by +A callback routine can be registered by calling + hotplug_memory_notifier(callback_func, priority) -The second argument of callback function (action) is event types of above. -The third argument is passed by pointer of struct memory_notify. +Callback functions with higher values of priority are called before callback +functions with lower values. + +A callback function must have the following prototype: + + int callback_func( + struct notifier_block *self, unsigned long action, void *arg); + +The first argument of the callback function (self) is a pointer to the block +of the notifier chain that points to the callback function itself. +The second argument (action) is one of the event types described above. +The third argument (arg) passes a pointer of struct memory_notify. struct memory_notify { unsigned long start_pfn; @@ -412,6 +425,18 @@ node loses all memory. If this is -1, then nodemask status is not changed. If status_changed_nid* >= 0, callback should create/discard structures for the node if necessary. +The callback routine shall return one of the values +NOTIFY_DONE, NOTIFY_OK, NOTIFY_BAD, NOTIFY_STOP +defined in include/linux/notifier.h + +NOTIFY_DONE and NOTIFY_OK have no effect on the further processing. + +NOTIFY_BAD is used as response to the MEM_GOING_ONLINE, MEM_GOING_OFFLINE, +MEM_ONLINE, or MEM_OFFLINE action to cancel hotplugging. It stops +further processing of the notification queue. + +NOTIFY_STOP stops further processing of the notification queue. + -------------- 9. Future Work --------------