workqueue: Convert to state machine callbacks

Get rid of the prio ordering of the separate notifiers and use a proper state
callback pair.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160713153335.197083890@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

5 files changed, 61 insertions, 74 deletions

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index ca2dd865a34e..797d9c8e9a1b 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -55,15 +55,6 @@ extern ssize_t arch_cpu_release(const char *, size_t);
 #endif
 struct notifier_block;
 
-/*
- * CPU notifier priorities.
- */
-enum {
-        /* bring up workqueues before normal notifiers and down after */
-        CPU_PRI_WORKQUEUE_UP    = 5,
-        CPU_PRI_WORKQUEUE_DOWN  = -5,
-};
-
 #define CPU_ONLINE              0x0002 /* CPU (unsigned)v is up */
 #define CPU_UP_PREPARE          0x0003 /* CPU (unsigned)v coming up */
 #define CPU_UP_CANCELED         0x0004 /* CPU (unsigned)v NOT coming up */
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index acfeda137df8..60557a9e783d 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -12,6 +12,7 @@ enum cpuhp_state {
         CPUHP_PERF_BFIN,
         CPUHP_PERF_POWER,
         CPUHP_PERF_SUPERH,
+        CPUHP_WORKQUEUE_PREP,
         CPUHP_NOTIFY_PREPARE,
         CPUHP_BRINGUP_CPU,
         CPUHP_AP_IDLE_DEAD,
@@ -49,6 +50,7 @@ enum cpuhp_state {
         CPUHP_AP_PERF_S390_SF_ONLINE,
         CPUHP_AP_PERF_ARM_CCI_ONLINE,
         CPUHP_AP_PERF_ARM_CCN_ONLINE,
+        CPUHP_AP_WORKQUEUE_ONLINE,
         CPUHP_AP_NOTIFY_ONLINE,
         CPUHP_AP_ONLINE_DYN,
         CPUHP_AP_ONLINE_DYN_END         = CPUHP_AP_ONLINE_DYN + 30,
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index ca73c503b92a..26cc1df280d6 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -625,4 +625,10 @@ void wq_watchdog_touch(int cpu);
 static inline void wq_watchdog_touch(int cpu) { }
 #endif  /* CONFIG_WQ_WATCHDOG */
 
+#ifdef CONFIG_SMP
+int workqueue_prepare_cpu(unsigned int cpu);
+int workqueue_online_cpu(unsigned int cpu);
+int workqueue_offline_cpu(unsigned int cpu);
+#endif
+
 #endif
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 3705d9043c08..af53f820fec9 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1185,6 +1185,11 @@ static struct cpuhp_step cpuhp_bp_states[] = {
                 .startup = perf_event_init_cpu,
                 .teardown = perf_event_exit_cpu,
         },
+        [CPUHP_WORKQUEUE_PREP] = {
+                .name = "workqueue prepare",
+                .startup = workqueue_prepare_cpu,
+                .teardown = NULL,
+        },
         /*
          * Preparatory and dead notifiers. Will be replaced once the notifiers
          * are converted to states.
@@ -1267,6 +1272,11 @@ static struct cpuhp_step cpuhp_ap_states[] = {
                 .startup = perf_event_init_cpu,
                 .teardown = perf_event_exit_cpu,
         },
+        [CPUHP_AP_WORKQUEUE_ONLINE] = {
+                .name = "workqueue online",
+                .startup = workqueue_online_cpu,
+                .teardown = workqueue_offline_cpu,
+        },
 
         /*
          * Online/down_prepare notifiers. Will be removed once the notifiers
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index e1c0e996b5ae..c9dd5fbdbf33 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -4611,84 +4611,65 @@ static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
                                                   pool->attrs->cpumask) < 0);
 }
 
-/*
- * Workqueues should be brought up before normal priority CPU notifiers.
- * This will be registered high priority CPU notifier.
- */
-static int workqueue_cpu_up_callback(struct notifier_block *nfb,
-                                               unsigned long action,
-                                               void *hcpu)
+int workqueue_prepare_cpu(unsigned int cpu)
+{
+        struct worker_pool *pool;
+
+        for_each_cpu_worker_pool(pool, cpu) {
+                if (pool->nr_workers)
+                        continue;
+                if (!create_worker(pool))
+                        return -ENOMEM;
+        }
+        return 0;
+}
+
+int workqueue_online_cpu(unsigned int cpu)
 {
-        int cpu = (unsigned long)hcpu;
         struct worker_pool *pool;
         struct workqueue_struct *wq;
         int pi;
 
-        switch (action & ~CPU_TASKS_FROZEN) {
-        case CPU_UP_PREPARE:
-                for_each_cpu_worker_pool(pool, cpu) {
-                        if (pool->nr_workers)
-                                continue;
-                        if (!create_worker(pool))
-                                return NOTIFY_BAD;
-                }
-                break;
-
-        case CPU_DOWN_FAILED:
-        case CPU_ONLINE:
-                mutex_lock(&wq_pool_mutex);
+        mutex_lock(&wq_pool_mutex);
 
-                for_each_pool(pool, pi) {
-                        mutex_lock(&pool->attach_mutex);
+        for_each_pool(pool, pi) {
+                mutex_lock(&pool->attach_mutex);
 
-                        if (pool->cpu == cpu)
-                                rebind_workers(pool);
-                        else if (pool->cpu < 0)
-                                restore_unbound_workers_cpumask(pool, cpu);
+                if (pool->cpu == cpu)
+                        rebind_workers(pool);
+                else if (pool->cpu < 0)
+                        restore_unbound_workers_cpumask(pool, cpu);
 
-                        mutex_unlock(&pool->attach_mutex);
-                }
+                mutex_unlock(&pool->attach_mutex);
+        }
 
-                /* update NUMA affinity of unbound workqueues */
-                list_for_each_entry(wq, &workqueues, list)
-                        wq_update_unbound_numa(wq, cpu, true);
+        /* update NUMA affinity of unbound workqueues */
+        list_for_each_entry(wq, &workqueues, list)
+                wq_update_unbound_numa(wq, cpu, true);
 
-                mutex_unlock(&wq_pool_mutex);
-                break;
-        }
-        return NOTIFY_OK;
+        mutex_unlock(&wq_pool_mutex);
+        return 0;
 }
 
-/*
- * Workqueues should be brought down after normal priority CPU notifiers.
- * This will be registered as low priority CPU notifier.
- */
-static int workqueue_cpu_down_callback(struct notifier_block *nfb,
-                                                 unsigned long action,
-                                                 void *hcpu)
+int workqueue_offline_cpu(unsigned int cpu)
 {
-        int cpu = (unsigned long)hcpu;
         struct work_struct unbind_work;
         struct workqueue_struct *wq;
 
-        switch (action & ~CPU_TASKS_FROZEN) {
-        case CPU_DOWN_PREPARE:
-                /* unbinding per-cpu workers should happen on the local CPU */
-                INIT_WORK_ONSTACK(&unbind_work, wq_unbind_fn);
-                queue_work_on(cpu, system_highpri_wq, &unbind_work);
-
-                /* update NUMA affinity of unbound workqueues */
-                mutex_lock(&wq_pool_mutex);
-                list_for_each_entry(wq, &workqueues, list)
-                        wq_update_unbound_numa(wq, cpu, false);
-                mutex_unlock(&wq_pool_mutex);
-
-                /* wait for per-cpu unbinding to finish */
-                flush_work(&unbind_work);
-                destroy_work_on_stack(&unbind_work);
-                break;
-        }
-        return NOTIFY_OK;
+        /* unbinding per-cpu workers should happen on the local CPU */
+        INIT_WORK_ONSTACK(&unbind_work, wq_unbind_fn);
+        queue_work_on(cpu, system_highpri_wq, &unbind_work);
+
+        /* update NUMA affinity of unbound workqueues */
+        mutex_lock(&wq_pool_mutex);
+        list_for_each_entry(wq, &workqueues, list)
+                wq_update_unbound_numa(wq, cpu, false);
+        mutex_unlock(&wq_pool_mutex);
+
+        /* wait for per-cpu unbinding to finish */
+        flush_work(&unbind_work);
+        destroy_work_on_stack(&unbind_work);
+        return 0;
 }
 
 #ifdef CONFIG_SMP
@@ -5490,9 +5471,6 @@ static int __init init_workqueues(void)
 
         pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
 
-        cpu_notifier(workqueue_cpu_up_callback, CPU_PRI_WORKQUEUE_UP);
-        hotcpu_notifier(workqueue_cpu_down_callback, CPU_PRI_WORKQUEUE_DOWN);
-
         wq_numa_init();
 
         /* initialize CPU pools */