workqueue: separate iteration role from worker_idr

worker_idr has the iteration (iterating for attached workers) and
worker ID duties. These two duties don't have to be tied together. We
can separate them and use a list for tracking attached workers and
iteration.

Before this separation, it wasn't possible to add rescuer workers to
worker_idr due to rescuer workers couldn't allocate ID dynamically
because ID-allocation depends on memory-allocation, which rescuer
can't depend on.

After separation, we can easily add the rescuer workers to the list for
iteration without any memory-allocation. It is required when we attach
the rescuer worker to the pool in later patch.

tj: Minor description updates.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/kernel/workqueue_internal.h b/kernel/workqueue_internal.h
index 7e2204db0b1a..8888e0672442 100644
--- a/kernel/workqueue_internal.h
+++ b/kernel/workqueue_internal.h
@@ -37,6 +37,8 @@ struct worker {
         struct task_struct      *task;          /* I: worker task */
         struct worker_pool      *pool;          /* I: the associated pool */
                                                 /* L: for rescuers */
+        struct list_head        node;           /* M: anchored at pool->workers */
+                                                /* M: runs through worker->node */
 
         unsigned long           last_active;    /* L: last active timestamp */
         unsigned int            flags;          /* X: flags */