[RFC v3 4/7] workqueue: use new hashtable implementation

[Sasha Levin <levinsasha928@gmail.com>]

Switch workqueues to use the new hashtable implementation. This reduces the amount of
generic unrelated code in the workqueues.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
---
 kernel/workqueue.c |   89 ++++++++++-----------------------------------------
 1 files changed, 18 insertions(+), 71 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 692d976..548fa87 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -41,6 +41,7 @@
 #include <linux/debug_locks.h>
 #include <linux/lockdep.h>
 #include <linux/idr.h>
+#include <linux/hashtable.h>
 
 #include "workqueue_sched.h"
 
@@ -82,8 +83,6 @@ enum {
 	NR_WORKER_POOLS		= 2,		/* # worker pools per gcwq */
 
 	BUSY_WORKER_HASH_ORDER	= 6,		/* 64 pointers */
-	BUSY_WORKER_HASH_SIZE	= 1 << BUSY_WORKER_HASH_ORDER,
-	BUSY_WORKER_HASH_MASK	= BUSY_WORKER_HASH_SIZE - 1,
 
 	MAX_IDLE_WORKERS_RATIO	= 4,		/* 1/4 of busy can be idle */
 	IDLE_WORKER_TIMEOUT	= 300 * HZ,	/* keep idle ones for 5 mins */
@@ -180,7 +179,7 @@ struct global_cwq {
 	unsigned int		flags;		/* L: GCWQ_* flags */
 
 	/* workers are chained either in busy_hash or pool idle_list */
-	struct hlist_head	busy_hash[BUSY_WORKER_HASH_SIZE];
+	DEFINE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
 						/* L: hash of busy workers */
 
 	struct worker_pool	pools[2];	/* normal and highpri pools */
@@ -288,8 +287,8 @@ EXPORT_SYMBOL_GPL(system_nrt_freezable_wq);
 	     (pool) < &(gcwq)->pools[NR_WORKER_POOLS]; (pool)++)
 
 #define for_each_busy_worker(worker, i, pos, gcwq)			\
-	for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++)			\
-		hlist_for_each_entry(worker, pos, &gcwq->busy_hash[i], hentry)
+	hash_for_each(gcwq->busy_hash, BUSY_WORKER_HASH_ORDER, i, pos,	\
+		worker, hentry)
 
 static inline int __next_gcwq_cpu(int cpu, const struct cpumask *mask,
 				  unsigned int sw)
@@ -822,63 +821,6 @@ static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
 }
 
 /**
- * busy_worker_head - return the busy hash head for a work
- * @gcwq: gcwq of interest
- * @work: work to be hashed
- *
- * Return hash head of @gcwq for @work.
- *
- * CONTEXT:
- * spin_lock_irq(gcwq->lock).
- *
- * RETURNS:
- * Pointer to the hash head.
- */
-static struct hlist_head *busy_worker_head(struct global_cwq *gcwq,
-					   struct work_struct *work)
-{
-	const int base_shift = ilog2(sizeof(struct work_struct));
-	unsigned long v = (unsigned long)work;
-
-	/* simple shift and fold hash, do we need something better? */
-	v >>= base_shift;
-	v += v >> BUSY_WORKER_HASH_ORDER;
-	v &= BUSY_WORKER_HASH_MASK;
-
-	return &gcwq->busy_hash[v];
-}
-
-/**
- * __find_worker_executing_work - find worker which is executing a work
- * @gcwq: gcwq of interest
- * @bwh: hash head as returned by busy_worker_head()
- * @work: work to find worker for
- *
- * Find a worker which is executing @work on @gcwq.  @bwh should be
- * the hash head obtained by calling busy_worker_head() with the same
- * work.
- *
- * CONTEXT:
- * spin_lock_irq(gcwq->lock).
- *
- * RETURNS:
- * Pointer to worker which is executing @work if found, NULL
- * otherwise.
- */
-static struct worker *__find_worker_executing_work(struct global_cwq *gcwq,
-						   struct hlist_head *bwh,
-						   struct work_struct *work)
-{
-	struct worker *worker;
-	struct hlist_node *tmp;
-
-	hlist_for_each_entry(worker, tmp, bwh, hentry)
-		if (worker->current_work == work)
-			return worker;
-	return NULL;
-}
-
-/**
  * find_worker_executing_work - find worker which is executing a work
  * @gcwq: gcwq of interest
  * @work: work to find worker for
@@ -897,8 +839,15 @@ static struct worker *__find_worker_executing_work(struct global_cwq *gcwq,
 static struct worker *find_worker_executing_work(struct global_cwq *gcwq,
 						 struct work_struct *work)
 {
-	return __find_worker_executing_work(gcwq, busy_worker_head(gcwq, work),
-					    work);
+	struct worker *worker;
+	struct hlist_node *tmp;
+
+	hash_for_each_possible(gcwq->busy_hash, worker, BUSY_WORKER_HASH_ORDER,
+						tmp, hentry, (unsigned long)work)
+		if (worker->current_work == work)
+			return worker;
+
+	return NULL;
 }
 
 /**
@@ -1932,7 +1881,6 @@ __acquires(&gcwq->lock)
 	struct cpu_workqueue_struct *cwq = get_work_cwq(work);
 	struct worker_pool *pool = worker->pool;
 	struct global_cwq *gcwq = pool->gcwq;
-	struct hlist_head *bwh = busy_worker_head(gcwq, work);
 	bool cpu_intensive = cwq->wq->flags & WQ_CPU_INTENSIVE;
 	work_func_t f = work->func;
 	int work_color;
@@ -1964,7 +1912,7 @@ __acquires(&gcwq->lock)
 	 * already processing the work.  If so, defer the work to the
 	 * currently executing one.
 	 */
-	collision = __find_worker_executing_work(gcwq, bwh, work);
+	collision = find_worker_executing_work(gcwq, work);
 	if (unlikely(collision)) {
 		move_linked_works(work, &collision->scheduled, NULL);
 		return;
@@ -1972,7 +1920,8 @@ __acquires(&gcwq->lock)
 
 	/* claim and process */
 	debug_work_deactivate(work);
-	hlist_add_head(&worker->hentry, bwh);
+	hash_add(gcwq->busy_hash, BUSY_WORKER_HASH_ORDER, &worker->hentry,
+			(unsigned long)worker);
 	worker->current_work = work;
 	worker->current_cwq = cwq;
 	work_color = get_work_color(work);
@@ -2027,7 +1976,7 @@ __acquires(&gcwq->lock)
 		worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
 
 	/* we're done with it, release */
-	hlist_del_init(&worker->hentry);
+	hash_del(&worker->hentry);
 	worker->current_work = NULL;
 	worker->current_cwq = NULL;
 	cwq_dec_nr_in_flight(cwq, work_color, false);
@@ -3690,7 +3639,6 @@ out_unlock:
 static int __init init_workqueues(void)
 {
 	unsigned int cpu;
-	int i;
 
 	cpu_notifier(workqueue_cpu_up_callback, CPU_PRI_WORKQUEUE_UP);
 	cpu_notifier(workqueue_cpu_down_callback, CPU_PRI_WORKQUEUE_DOWN);
@@ -3704,8 +3652,7 @@ static int __init init_workqueues(void)
 		gcwq->cpu = cpu;
 		gcwq->flags |= GCWQ_DISASSOCIATED;
 
-		for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++)
-			INIT_HLIST_HEAD(&gcwq->busy_hash[i]);
+		hash_init(gcwq->busy_hash, BUSY_WORKER_HASH_ORDER);
 
 		for_each_worker_pool(pool, gcwq) {
 			pool->gcwq = gcwq;
-- 
1.7.8.6