MINOR: task: introduce work lists
Sometimes we need to delegate some list processing to a function running
on another thread. In this case the list element will simply be queued
into a dedicated self-locked list and the task responsible for this list
will be woken up, calling the associated function which will run over the
list.
This is what work_list does. Such lists will be dedicated to a limited
type of work but will significantly ease such remote handling. A function
is provided to create these per-thread lists, their tasks and to properly
bind each task to a distinct thread, so that the caller only has to store
the resulting pointer to the start of the structure.
These structures should not be abused though as each head will consume
4 pointers per thread, hence 32 bytes per thread or 2 kB for 64 threads.
diff --git a/include/types/task.h b/include/types/task.h
index ab909d0..a949058 100644
--- a/include/types/task.h
+++ b/include/types/task.h
@@ -106,6 +106,23 @@
* expire timer. The scheduler will requeue the task at the proper location.
*/
+
+/* A work_list is a thread-safe way to enqueue some work to be run on another
+ * thread. It consists of a list, a task and a general-purpose argument.
+ * A work is appended to the list by atomically adding a list element to the
+ * list and waking up the associated task, which is done using work_add(). The
+ * caller must be careful about how operations are run as it will definitely
+ * happen that the element being enqueued is processed by the other thread
+ * before the call returns. Some locking conventions between the caller and the
+ * callee might sometimes be necessary. The task is always woken up with reason
+ * TASK_WOKEN_OTHER and a context pointing to the work_list entry.
+ */
+struct work_list {
+ struct list head;
+ struct task *task;
+ void *arg;
+};
+
#endif /* _TYPES_TASK_H */
/*