async: keep pending tasks on async_domain and remove async_pending

Async kept single global pending list and per-domain running lists.
When an async item is queued, it's put on the global pending list.
The item is moved to the per-domain running list when its execution
starts.

At this point, this design complicates execution and synchronization
without bringing any benefit.  The list only matters for
synchronization which doesn't care whether a given async item is
pending or executing.  Also, global synchronization is done by
iterating through all active registered async_domains, so the global
async_pending list doesn't help anything either.

Rename async_domain->running to async_domain->pending and put async
items directly there and remove when execution completes.  This
simplifies lowest_in_progress() a lot - the first item on the pending
list is the one with the lowest cookie, and async_run_entry_fn()
doesn't have to mess with moving the item from pending to running.

After the change, whether a domain is empty or not can be trivially
determined by looking at async_domain->pending.  Remove
async_domain->count and use list_empty() on pending instead.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Dan Williams <djbw@fb.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 6 deletions

diff --git a/include/linux/async.h b/include/linux/async.h
index 34ff5c610e0..a2e3f18b2ad 100644
--- a/include/linux/async.h
+++ b/include/linux/async.h
@@ -19,8 +19,7 @@ typedef u64 async_cookie_t;
 typedef void (async_func_ptr) (void *data, async_cookie_t cookie);
 struct async_domain {
 	struct list_head node;
-	struct list_head running;
-	int count;
+	struct list_head pending;
 	unsigned registered:1;
 };
 
@@ -29,8 +28,7 @@ struct async_domain {
  */
 #define ASYNC_DOMAIN(_name) \
 	struct async_domain _name = { .node = LIST_HEAD_INIT(_name.node), \
-				      .running = LIST_HEAD_INIT(_name.running), \
-				      .count = 0, \
+				      .pending = LIST_HEAD_INIT(_name.pending), \
 				      .registered = 1 }
 
 /*
@@ -39,8 +37,7 @@ struct async_domain {
  */
 #define ASYNC_DOMAIN_EXCLUSIVE(_name) \
 	struct async_domain _name = { .node = LIST_HEAD_INIT(_name.node), \
-				      .running = LIST_HEAD_INIT(_name.running), \
-				      .count = 0, \
+				      .pending = LIST_HEAD_INIT(_name.pending), \
 				      .registered = 0 }
 
 extern async_cookie_t async_schedule(async_func_ptr *ptr, void *data);