infiniband: Ehca: Use hotplug thread infrastructure

Get rid of the hotplug notifiers and use the generic hotplug thread
infrastructure.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/20120716103948.775527032@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 92 insertions, 164 deletions

diff --git a/drivers/infiniband/hw/ehca/ehca_irq.c b/drivers/infiniband/hw/ehca/ehca_irq.c
index 53589000fd07..4eeac40cd943 100644
--- a/drivers/infiniband/hw/ehca/ehca_irq.c
+++ b/drivers/infiniband/hw/ehca/ehca_irq.c
@@ -42,6 +42,7 @@
  */
 
 #include <linux/slab.h>
+#include <linux/smpboot.h>
 
 #include "ehca_classes.h"
 #include "ehca_irq.h"
@@ -652,7 +653,7 @@ void ehca_tasklet_eq(unsigned long data)
         ehca_process_eq((struct ehca_shca*)data, 1);
 }
 
-static inline int find_next_online_cpu(struct ehca_comp_pool *pool)
+static int find_next_online_cpu(struct ehca_comp_pool *pool)
 {
         int cpu;
         unsigned long flags;
@@ -662,17 +663,20 @@ static inline int find_next_online_cpu(struct ehca_comp_pool *pool)
                 ehca_dmp(cpu_online_mask, cpumask_size(), "");
 
         spin_lock_irqsave(&pool->last_cpu_lock, flags);
-        cpu = cpumask_next(pool->last_cpu, cpu_online_mask);
-        if (cpu >= nr_cpu_ids)
-                cpu = cpumask_first(cpu_online_mask);
-        pool->last_cpu = cpu;
+        do {
+                cpu = cpumask_next(pool->last_cpu, cpu_online_mask);
+                if (cpu >= nr_cpu_ids)
+                        cpu = cpumask_first(cpu_online_mask);
+                pool->last_cpu = cpu;
+        } while (!per_cpu_ptr(pool->cpu_comp_tasks, cpu)->active)
         spin_unlock_irqrestore(&pool->last_cpu_lock, flags);
 
         return cpu;
 }
 
 static void __queue_comp_task(struct ehca_cq *__cq,
-                              struct ehca_cpu_comp_task *cct)
+                              struct ehca_cpu_comp_task *cct,
+                              struct task_struct *thread)
 {
         unsigned long flags;
 
@@ -683,7 +687,7 @@ static void __queue_comp_task(struct ehca_cq *__cq,
                 __cq->nr_callbacks++;
                 list_add_tail(&__cq->entry, &cct->cq_list);
                 cct->cq_jobs++;
-                wake_up(&cct->wait_queue);
+                wake_up_process(thread);
         } else
                 __cq->nr_callbacks++;
 
@@ -695,6 +699,7 @@ static void queue_comp_task(struct ehca_cq *__cq)
 {
         int cpu_id;
         struct ehca_cpu_comp_task *cct;
+        struct task_struct *thread;
         int cq_jobs;
         unsigned long flags;
 
@@ -702,7 +707,8 @@ static void queue_comp_task(struct ehca_cq *__cq)
         BUG_ON(!cpu_online(cpu_id));
 
         cct = per_cpu_ptr(pool->cpu_comp_tasks, cpu_id);
-        BUG_ON(!cct);
+        thread = per_cpu_ptr(pool->cpu_comp_threads, cpu_id);
+        BUG_ON(!cct || !thread);
 
         spin_lock_irqsave(&cct->task_lock, flags);
         cq_jobs = cct->cq_jobs;
@@ -710,28 +716,25 @@ static void queue_comp_task(struct ehca_cq *__cq)
         if (cq_jobs > 0) {
                 cpu_id = find_next_online_cpu(pool);
                 cct = per_cpu_ptr(pool->cpu_comp_tasks, cpu_id);
-                BUG_ON(!cct);
+                thread = per_cpu_ptr(pool->cpu_comp_threads, cpu_id);
+                BUG_ON(!cct || !thread);
         }
-
-        __queue_comp_task(__cq, cct);
+        __queue_comp_task(__cq, cct, thread);
 }
 
 static void run_comp_task(struct ehca_cpu_comp_task *cct)
 {
         struct ehca_cq *cq;
-        unsigned long flags;
-
-        spin_lock_irqsave(&cct->task_lock, flags);
 
         while (!list_empty(&cct->cq_list)) {
                 cq = list_entry(cct->cq_list.next, struct ehca_cq, entry);
-                spin_unlock_irqrestore(&cct->task_lock, flags);
+                spin_unlock_irq(&cct->task_lock);
 
                 comp_event_callback(cq);
                 if (atomic_dec_and_test(&cq->nr_events))
                         wake_up(&cq->wait_completion);
 
-                spin_lock_irqsave(&cct->task_lock, flags);
+                spin_lock_irq(&cct->task_lock);
                 spin_lock(&cq->task_lock);
                 cq->nr_callbacks--;
                 if (!cq->nr_callbacks) {
@@ -740,159 +743,76 @@ static void run_comp_task(struct ehca_cpu_comp_task *cct)
                 }
                 spin_unlock(&cq->task_lock);
         }
-
-        spin_unlock_irqrestore(&cct->task_lock, flags);
 }
 
-static int comp_task(void *__cct)
+static void comp_task_park(unsigned int cpu)
 {
-        struct ehca_cpu_comp_task *cct = __cct;
-        int cql_empty;
-        DECLARE_WAITQUEUE(wait, current);
-
-        set_current_state(TASK_INTERRUPTIBLE);
-        while (!kthread_should_stop()) {
-                add_wait_queue(&cct->wait_queue, &wait);
-
-                spin_lock_irq(&cct->task_lock);
-                cql_empty = list_empty(&cct->cq_list);
-                spin_unlock_irq(&cct->task_lock);
-                if (cql_empty)
-                        schedule();
-                else
-                        __set_current_state(TASK_RUNNING);
-
-                remove_wait_queue(&cct->wait_queue, &wait);
+        struct ehca_cpu_comp_task *cct = per_cpu_ptr(pool->cpu_comp_tasks, cpu);
+        struct ehca_cpu_comp_task *target;
+        struct task_struct *thread;
+        struct ehca_cq *cq, *tmp;
+        LIST_HEAD(list);
 
-                spin_lock_irq(&cct->task_lock);
-                cql_empty = list_empty(&cct->cq_list);
-                spin_unlock_irq(&cct->task_lock);
-                if (!cql_empty)
-                        run_comp_task(__cct);
+        spin_lock_irq(&cct->task_lock);
+        cct->cq_jobs = 0;
+        cct->active = 0;
+        list_splice_init(&cct->cq_list, &list);
+        spin_unlock_irq(&cct->task_lock);
 
-                set_current_state(TASK_INTERRUPTIBLE);
+        cpu = find_next_online_cpu(pool);
+        target = per_cpu_ptr(pool->cpu_comp_tasks, cpu);
+        thread = per_cpu_ptr(pool->cpu_comp_threads, cpu);
+        spin_lock_irq(&target->task_lock);
+        list_for_each_entry_safe(cq, tmp, &list, entry) {
+                list_del(&cq->entry);
+                __queue_comp_task(cq, target, thread);
         }
-        __set_current_state(TASK_RUNNING);
-
-        return 0;
-}
-
-static struct task_struct *create_comp_task(struct ehca_comp_pool *pool,
-                                            int cpu)
-{
-        struct ehca_cpu_comp_task *cct;
-
-        cct = per_cpu_ptr(pool->cpu_comp_tasks, cpu);
-        spin_lock_init(&cct->task_lock);
-        INIT_LIST_HEAD(&cct->cq_list);
-        init_waitqueue_head(&cct->wait_queue);
-        cct->task = kthread_create_on_node(comp_task, cct, cpu_to_node(cpu),
-                                           "ehca_comp/%d", cpu);
-
-        return cct->task;
+        spin_unlock_irq(&target->task_lock);
 }
 
-static void destroy_comp_task(struct ehca_comp_pool *pool,
-                              int cpu)
+static void comp_task_stop(unsigned int cpu, bool online)
 {
-        struct ehca_cpu_comp_task *cct;
-        struct task_struct *task;
-        unsigned long flags_cct;
-
-        cct = per_cpu_ptr(pool->cpu_comp_tasks, cpu);
-
-        spin_lock_irqsave(&cct->task_lock, flags_cct);
+        struct ehca_cpu_comp_task *cct = per_cpu_ptr(pool->cpu_comp_tasks, cpu);
 
-        task = cct->task;
-        cct->task = NULL;
+        spin_lock_irq(&cct->task_lock);
         cct->cq_jobs = 0;
-
-        spin_unlock_irqrestore(&cct->task_lock, flags_cct);
-
-        if (task)
-                kthread_stop(task);
+        cct->active = 0;
+        WARN_ON(!list_empty(&cct->cq_list));
+        spin_unlock_irq(&cct->task_lock);
 }
 
-static void __cpuinit take_over_work(struct ehca_comp_pool *pool, int cpu)
+static int comp_task_should_run(unsigned int cpu)
 {
         struct ehca_cpu_comp_task *cct = per_cpu_ptr(pool->cpu_comp_tasks, cpu);
-        LIST_HEAD(list);
-        struct ehca_cq *cq;
-        unsigned long flags_cct;
-
-        spin_lock_irqsave(&cct->task_lock, flags_cct);
-
-        list_splice_init(&cct->cq_list, &list);
-
-        while (!list_empty(&list)) {
-                cq = list_entry(cct->cq_list.next, struct ehca_cq, entry);
-
-                list_del(&cq->entry);
-                __queue_comp_task(cq, this_cpu_ptr(pool->cpu_comp_tasks));
-        }
-
-        spin_unlock_irqrestore(&cct->task_lock, flags_cct);
 
+        return cct->cq_jobs;
 }
 
-static int __cpuinit comp_pool_callback(struct notifier_block *nfb,
-                                        unsigned long action,
-                                        void *hcpu)
+static int comp_task(unsigned int cpu)
 {
-        unsigned int cpu = (unsigned long)hcpu;
-        struct ehca_cpu_comp_task *cct;
+        struct ehca_cpu_comp_task *cct = this_cpu_ptr(pool->cpu_comp_tasks);
+        int cql_empty;
 
-        switch (action) {
-        case CPU_UP_PREPARE:
-        case CPU_UP_PREPARE_FROZEN:
-                ehca_gen_dbg("CPU: %x (CPU_PREPARE)", cpu);
-                if (!create_comp_task(pool, cpu)) {
-                        ehca_gen_err("Can't create comp_task for cpu: %x", cpu);
-                        return notifier_from_errno(-ENOMEM);
-                }
-                break;
-        case CPU_UP_CANCELED:
-        case CPU_UP_CANCELED_FROZEN:
-                ehca_gen_dbg("CPU: %x (CPU_CANCELED)", cpu);
-                cct = per_cpu_ptr(pool->cpu_comp_tasks, cpu);
-                kthread_bind(cct->task, cpumask_any(cpu_online_mask));
-                destroy_comp_task(pool, cpu);
-                break;
-        case CPU_ONLINE:
-        case CPU_ONLINE_FROZEN:
-                ehca_gen_dbg("CPU: %x (CPU_ONLINE)", cpu);
-                cct = per_cpu_ptr(pool->cpu_comp_tasks, cpu);
-                kthread_bind(cct->task, cpu);
-                wake_up_process(cct->task);
-                break;
-        case CPU_DOWN_PREPARE:
-        case CPU_DOWN_PREPARE_FROZEN:
-                ehca_gen_dbg("CPU: %x (CPU_DOWN_PREPARE)", cpu);
-                break;
-        case CPU_DOWN_FAILED:
-        case CPU_DOWN_FAILED_FROZEN:
-                ehca_gen_dbg("CPU: %x (CPU_DOWN_FAILED)", cpu);
-                break;
-        case CPU_DEAD:
-        case CPU_DEAD_FROZEN:
-                ehca_gen_dbg("CPU: %x (CPU_DEAD)", cpu);
-                destroy_comp_task(pool, cpu);
-                take_over_work(pool, cpu);
-                break;
+        spin_lock_irq(&cct->task_lock);
+        cql_empty = list_empty(&cct->cq_list);
+        if (!cql_empty) {
+                __set_current_state(TASK_RUNNING);
+                run_comp_task(cct);
         }
-
-        return NOTIFY_OK;
+        spin_unlock_irq(&cct->task_lock);
 }
 
-static struct notifier_block comp_pool_callback_nb __cpuinitdata = {
-        .notifier_call  = comp_pool_callback,
-        .priority       = 0,
+static struct smp_hotplug_thread comp_pool_threads = {
+        .thread_should_run      = comp_task_should_run,
+        .thread_fn              = comp_task,
+        .thread_comm            = "ehca_comp/%u",
+        .cleanup                = comp_task_stop,
+        .park                   = comp_task_park,
 };
 
 int ehca_create_comp_pool(void)
 {
-        int cpu;
-        struct task_struct *task;
+        int cpu, ret = -ENOMEM;
 
         if (!ehca_scaling_code)
                 return 0;
@@ -905,38 +825,46 @@ int ehca_create_comp_pool(void)
         pool->last_cpu = cpumask_any(cpu_online_mask);
 
         pool->cpu_comp_tasks = alloc_percpu(struct ehca_cpu_comp_task);
-        if (pool->cpu_comp_tasks == NULL) {
-                kfree(pool);
-                return -EINVAL;
-        }
+        if (!pool->cpu_comp_tasks)
+                goto out_pool;
 
-        for_each_online_cpu(cpu) {
-                task = create_comp_task(pool, cpu);
-                if (task) {
-                        kthread_bind(task, cpu);
-                        wake_up_process(task);
-                }
+        pool->cpu_comp_threads = alloc_percpu(struct task_struct *);
+        if (!pool->cpu_comp_threads)
+                goto out_tasks;
+
+        for_each_present_cpu(cpu) {
+                struct ehca_cpu_comp_task *cct;
+
+                cct = per_cpu_ptr(pool->cpu_comp_tasks, cpu);
+                spin_lock_init(&cct->task_lock);
+                INIT_LIST_HEAD(&cct->cq_list);
         }
 
-        register_hotcpu_notifier(&comp_pool_callback_nb);
+        comp_pool_threads.store = pool->cpu_comp_threads;
+        ret = smpboot_register_percpu_thread(&comp_pool_threads);
+        if (ret)
+                goto out_threads;
 
-        printk(KERN_INFO "eHCA scaling code enabled\n");
+        pr_info("eHCA scaling code enabled\n");
+        return ret;
 
-        return 0;
+out_threads:
+        free_percpu(pool->cpu_comp_threads);
+out_tasks:
+        free_percpu(pool->cpu_comp_tasks);
+out_pool:
+        kfree(pool);
+        return ret;
 }
 
 void ehca_destroy_comp_pool(void)
 {
-        int i;
-
         if (!ehca_scaling_code)
                 return;
 
-        unregister_hotcpu_notifier(&comp_pool_callback_nb);
-
-        for_each_online_cpu(i)
-                destroy_comp_task(pool, i);
+        smpboot_unregister_percpu_thread(&comp_pool_threads);
 
+        free_percpu(pool->cpu_comp_threads);
         free_percpu(pool->cpu_comp_tasks);
         kfree(pool);
 }
diff --git a/drivers/infiniband/hw/ehca/ehca_irq.h b/drivers/infiniband/hw/ehca/ehca_irq.h
index 3346cb06cea6..5370199f08c7 100644
--- a/drivers/infiniband/hw/ehca/ehca_irq.h
+++ b/drivers/infiniband/hw/ehca/ehca_irq.h
@@ -58,15 +58,15 @@ void ehca_tasklet_eq(unsigned long data);
 void ehca_process_eq(struct ehca_shca *shca, int is_irq);
 
 struct ehca_cpu_comp_task {
-        wait_queue_head_t wait_queue;
         struct list_head cq_list;
-        struct task_struct *task;
         spinlock_t task_lock;
         int cq_jobs;
+        int active;
 };
 
 struct ehca_comp_pool {
-        struct ehca_cpu_comp_task *cpu_comp_tasks;
+        struct ehca_cpu_comp_task __percpu *cpu_comp_tasks;
+        struct task_struct * __percpu *cpu_comp_threads;
         int last_cpu;
         spinlock_t last_cpu_lock;
 };