workqueue: use new hashtable implementation

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

This patch depends on d9b482c ("hashtable: introduce a small and naive
hashtable") which was merged in v3.6.

Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 15 insertions, 71 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index fbc6576a83c3..acd417be8199 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];
+        DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
                                                 /* L: hash of busy workers */
 
         struct worker_pool      pools[NR_WORKER_POOLS];
@@ -285,8 +284,7 @@ EXPORT_SYMBOL_GPL(system_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, i, pos, worker, hentry)
 
 static inline int __next_gcwq_cpu(int cpu, const struct cpumask *mask,
                                   unsigned int sw)
@@ -859,63 +857,6 @@ 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
@@ -934,8 +875,14 @@ 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, tmp, hentry, (unsigned long)work)
+                if (worker->current_work == work)
+                        return worker;
+
+        return NULL;
 }
 
 /**
@@ -2166,7 +2113,6 @@ __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;
@@ -2198,7 +2144,7 @@ __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;
@@ -2206,7 +2152,7 @@ __acquires(&gcwq->lock)
 
         /* claim and dequeue */
         debug_work_deactivate(work);
-        hlist_add_head(&worker->hentry, bwh);
+        hash_add(gcwq->busy_hash, &worker->hentry, (unsigned long)worker);
         worker->current_work = work;
         worker->current_cwq = cwq;
         work_color = get_work_color(work);
@@ -2264,7 +2210,7 @@ __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);
@@ -3831,7 +3777,6 @@ out_unlock:
 static int __init init_workqueues(void)
 {
         unsigned int cpu;
-        int i;
 
         /* make sure we have enough bits for OFFQ CPU number */
         BUILD_BUG_ON((1LU << (BITS_PER_LONG - WORK_OFFQ_CPU_SHIFT)) <
@@ -3849,8 +3794,7 @@ 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);
 
                 for_each_worker_pool(pool, gcwq) {
                         pool->gcwq = gcwq;