workqueue: make GCWQ_FREEZING a pool flag

Make GCWQ_FREEZING a pool flag POOL_FREEZING.  This patch doesn't
change locking - FREEZING on both pools of a CPU are set or clear
together while holding gcwq->lock.  It shouldn't cause any functional
difference.

This leaves gcwq->flags w/o any flags.  Removed.

While at it, convert BUG_ON()s in freeze_workqueue_begin() and
thaw_workqueues() to WARN_ON_ONCE().

This is part of an effort to remove global_cwq and make worker_pool
the top level abstraction, which in turn will help implementing worker
pools with user-specified attributes.

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

1 files changed, 15 insertions, 13 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 1b8af92cc2c9..1a686e481132 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -47,11 +47,6 @@
 
 enum {
         /*
-         * global_cwq flags
-         */
-        GCWQ_FREEZING           = 1 << 1,       /* freeze in progress */
-
-        /*
          * worker_pool flags
          *
          * A bound pool is either associated or disassociated with its CPU.
@@ -70,6 +65,7 @@ enum {
         POOL_MANAGE_WORKERS     = 1 << 0,       /* need to manage workers */
         POOL_MANAGING_WORKERS   = 1 << 1,       /* managing workers */
         POOL_DISASSOCIATED      = 1 << 2,       /* cpu can't serve workers */
+        POOL_FREEZING           = 1 << 3,       /* freeze in progress */
 
         /* worker flags */
         WORKER_STARTED          = 1 << 0,       /* started */
@@ -152,7 +148,6 @@ struct worker_pool {
 struct global_cwq {
         spinlock_t              lock;           /* the gcwq lock */
         unsigned int            cpu;            /* I: the associated cpu */
-        unsigned int            flags;          /* L: GCWQ_* flags */
 
         /* workers are chained either in busy_hash or pool idle_list */
         DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
@@ -3380,13 +3375,15 @@ void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
         wq->saved_max_active = max_active;
 
         for_each_cwq_cpu(cpu, wq) {
-                struct global_cwq *gcwq = get_gcwq(cpu);
+                struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
+                struct worker_pool *pool = cwq->pool;
+                struct global_cwq *gcwq = pool->gcwq;
 
                 spin_lock_irq(&gcwq->lock);
 
                 if (!(wq->flags & WQ_FREEZABLE) ||
-                    !(gcwq->flags & GCWQ_FREEZING))
-                        cwq_set_max_active(get_cwq(gcwq->cpu, wq), max_active);
+                    !(pool->flags & POOL_FREEZING))
+                        cwq_set_max_active(cwq, max_active);
 
                 spin_unlock_irq(&gcwq->lock);
         }
@@ -3676,12 +3673,15 @@ void freeze_workqueues_begin(void)
 
         for_each_gcwq_cpu(cpu) {
                 struct global_cwq *gcwq = get_gcwq(cpu);
+                struct worker_pool *pool;
                 struct workqueue_struct *wq;
 
                 spin_lock_irq(&gcwq->lock);
 
-                BUG_ON(gcwq->flags & GCWQ_FREEZING);
-                gcwq->flags |= GCWQ_FREEZING;
+                for_each_worker_pool(pool, gcwq) {
+                        WARN_ON_ONCE(pool->flags & POOL_FREEZING);
+                        pool->flags |= POOL_FREEZING;
+                }
 
                 list_for_each_entry(wq, &workqueues, list) {
                         struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
@@ -3767,8 +3767,10 @@ void thaw_workqueues(void)
 
                 spin_lock_irq(&gcwq->lock);
 
-                BUG_ON(!(gcwq->flags & GCWQ_FREEZING));
-                gcwq->flags &= ~GCWQ_FREEZING;
+                for_each_worker_pool(pool, gcwq) {
+                        WARN_ON_ONCE(!(pool->flags & POOL_FREEZING));
+                        pool->flags &= ~POOL_FREEZING;
+                }
 
                 list_for_each_entry(wq, &workqueues, list) {
                         struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);