[RFC patch 5/5] infiniband: ehca: Use hotplug thread infrastructure

Thomas Gleixner
2012-06-13T11:01:31Z

[-- Attachment #1: infiniband-ehca-use-smp-threads.patch --]
[-- Type: text/plain, Size: 9759 bytes --]

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

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
drivers/infiniband/hw/ehca/ehca_irq.c | 240 ++++++++++++----------------------
drivers/infiniband/hw/ehca/ehca_irq.h | 5
2 files changed, 92 insertions(+), 153 deletions(-)

Index: tip/drivers/infiniband/hw/ehca/ehca_irq.c
===================================================================
--- tip.orig/drivers/infiniband/hw/ehca/ehca_irq.c
+++ tip/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;
@@ -662,10 +663,15 @@ static inline int find_next_online_cpu(s
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;
+ while (1) {
+ cpu = cpumask_next(pool->last_cpu, cpu_online_mask);
+ if (cpu >= nr_cpu_ids)
+ cpu = cpumask_first(cpu_online_mask);
+ pool->last_cpu = cpu;
+ /* Might be on the way out */
+ if (per_cpu_ptr(pool->cpu_comp_tasks, cpu)->active)
+ break;
+ }
spin_unlock_irqrestore(&pool->last_cpu_lock, flags);

return cpu;
@@ -719,19 +725,18 @@ static void queue_comp_task(struct ehca_
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);
+ spin_lock_irq(&cct->task_lock);

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) {
@@ -741,17 +746,51 @@ static void run_comp_task(struct ehca_cp
spin_unlock(&cq->task_lock);
}

- spin_unlock_irqrestore(&cct->task_lock, flags);
+ spin_unlock_irq(&cct->task_lock);
}

-static int comp_task(void *__cct)
+static void comp_task_park(unsigned int cpu)
{
- struct ehca_cpu_comp_task *cct = __cct;
- int cql_empty;
+ struct ehca_cpu_comp_task *cct = per_cpu_ptr(pool->cpu_comp_tasks, cpu);
+ struct ehca_cpu_comp_task *target;
+ struct ehca_cq *cq, *tmp;
+ LIST_HEAD(list);
+
+ 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);
+
+ cpu = find_next_online_cpu(pool);
+ target = per_cpu_ptr(pool->cpu_comp_tasks, 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);
+ }
+ spin_unlock_irq(&target->task_lock);
+}
+
+static void comp_task_stop(unsigned int cpu, bool online)
+{
+ struct ehca_cpu_comp_task *cct = per_cpu_ptr(pool->cpu_comp_tasks, cpu);
+
+ spin_lock_irq(&cct->task_lock);
+ cct->cq_jobs = 0;
+ cct->active = 0;
+ WARN_ON(!list_empty(&cct->cq_list));
+ spin_unlock_irq(&cct->task_lock);
+}
+
+static int comp_task(void *td)
+{
+ struct ehca_cpu_comp_task *cct = this_cpu_ptr(pool->cpu_comp_tasks);
DECLARE_WAITQUEUE(wait, current);
+ int cql_empty;

- set_current_state(TASK_INTERRUPTIBLE);
- while (!kthread_should_stop()) {
+ while (!smpboot_thread_check_parking(td)) {
+ set_current_state(TASK_INTERRUPTIBLE);
add_wait_queue(&cct->wait_queue, &wait);

spin_lock_irq(&cct->task_lock);
@@ -768,131 +807,21 @@ static int comp_task(void *__cct)
cql_empty = list_empty(&cct->cq_list);
spin_unlock_irq(&cct->task_lock);
if (!cql_empty)
- run_comp_task(__cct);
-
- set_current_state(TASK_INTERRUPTIBLE);
+ run_comp_task(cct);
}
- __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;
-}
-
-static void destroy_comp_task(struct ehca_comp_pool *pool,
- int cpu)
-{
- 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);
-
- task = cct->task;
- cct->task = NULL;
- cct->cq_jobs = 0;
-
- spin_unlock_irqrestore(&cct->task_lock, flags_cct);
-
- if (task)
- kthread_stop(task);
-}
-
-static void __cpuinit take_over_work(struct ehca_comp_pool *pool, 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);
-
-}
-
-static int __cpuinit comp_pool_callback(struct notifier_block *nfb,
- unsigned long action,
- void *hcpu)
-{
- unsigned int cpu = (unsigned long)hcpu;
- struct ehca_cpu_comp_task *cct;
-
- 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;
- }
-
- return NOTIFY_OK;
-}
-
-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_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 +834,47 @@ 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);
+ init_waitqueue_head(&cct->wait_queue);
}

- 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);
}
Index: tip/drivers/infiniband/hw/ehca/ehca_irq.h
===================================================================
--- tip.orig/drivers/infiniband/hw/ehca/ehca_irq.h
+++ tip/drivers/infiniband/hw/ehca/ehca_irq.h
@@ -60,13 +60,14 @@ void ehca_process_eq(struct ehca_shca *s
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;
};