commit 1a7a93bd33f48a369de29f6f2b56251127bf6ab4
author Tim Murray <timmurray@google.com> Mon Jul 25 19:21:17 2016 -0700
committer Tim Murray <timmurray@google.com> Thu Jul 28 11:31:18 2016 -0700
tree cd21cd5e393b1f7312dee8541721c28ddeaf7143
parent df8fac5bafe7033a600c8e75370d3f7cab1ddcc0

kgsl: convert some workqueues to use kthreads

adreno_dispatch_work and _kgsl_event_worker are both low-latency
low-runtime functions that are in the critical path of GPU
rendering. Moving them out of workqueues and into a dedicated FIFO
kthread avoids significant jitter.

bug 30342017

Change-Id: I5feb4e829064d422b4b9af2acb449afd1f981899

drivers/gpu/msm/adreno_dispatch.c

diff --git a/drivers/gpu/msm/adreno_dispatch.c b/drivers/gpu/msm/adreno_dispatch.c
index 5d3b2b8..67fd2f2 100644
--- a/drivers/gpu/msm/adreno_dispatch.c
+++ b/drivers/gpu/msm/adreno_dispatch.c
@@ -2096,7 +2096,7 @@
 	mutex_unlock(&device->mutex);
 }
 
-static void adreno_dispatcher_work(struct work_struct *work)
+static void adreno_dispatcher_work(struct kthread_work *work)
 {
 	struct adreno_dispatcher *dispatcher =
 		container_of(work, struct adreno_dispatcher, work);
@@ -2156,7 +2156,7 @@
 	struct adreno_device *adreno_dev = ADRENO_DEVICE(device);
 	struct adreno_dispatcher *dispatcher = &adreno_dev->dispatcher;
 
-	kgsl_schedule_work(&dispatcher->work);
+	queue_kthread_work(&kgsl_driver.worker, &dispatcher->work);
 }
 
 /**
@@ -2438,7 +2438,7 @@
 	setup_timer(&dispatcher->fault_timer, adreno_dispatcher_fault_timer,
 		(unsigned long) adreno_dev);
 
-	INIT_WORK(&dispatcher->work, adreno_dispatcher_work);
+	init_kthread_work(&dispatcher->work, adreno_dispatcher_work);
 
 	init_completion(&dispatcher->idle_gate);
 	complete_all(&dispatcher->idle_gate);

drivers/gpu/msm/adreno_dispatch.h

diff --git a/drivers/gpu/msm/adreno_dispatch.h b/drivers/gpu/msm/adreno_dispatch.h
index 699c3e4..fee4317 100644
--- a/drivers/gpu/msm/adreno_dispatch.h
+++ b/drivers/gpu/msm/adreno_dispatch.h
@@ -91,7 +91,7 @@
 	atomic_t fault;
 	struct plist_head pending;
 	spinlock_t plist_lock;
-	struct work_struct work;
+	struct kthread_work work;
 	struct kobject kobj;
 	struct completion idle_gate;
 	unsigned int disp_preempt_fair_sched;

drivers/gpu/msm/kgsl.c

diff --git a/drivers/gpu/msm/kgsl.c b/drivers/gpu/msm/kgsl.c
index 92ec8083..25f1f9d 100644
--- a/drivers/gpu/msm/kgsl.c
+++ b/drivers/gpu/msm/kgsl.c
@@ -4037,6 +4037,8 @@
 static int __init kgsl_core_init(void)
 {
 	int result = 0;
+	struct sched_param param = { .sched_priority = 2 };
+
 	/* alloc major and minor device numbers */
 	result = alloc_chrdev_region(&kgsl_driver.major, 0, KGSL_DEVICE_MAX,
 		"kgsl");
@@ -4101,6 +4103,18 @@
 	kgsl_driver.mem_workqueue = alloc_workqueue("kgsl-mementry",
 		WQ_UNBOUND | WQ_MEM_RECLAIM, 0);
 
+	init_kthread_worker(&kgsl_driver.worker);
+
+	kgsl_driver.worker_thread = kthread_run(kthread_worker_fn,
+		&kgsl_driver.worker, "kgsl_worker_thread");
+
+	if (IS_ERR(kgsl_driver.worker_thread)) {
+		pr_err("unable to start kgsl thread\n");
+		goto err;
+	}
+
+	sched_setscheduler(kgsl_driver.worker_thread, SCHED_FIFO, &param);
+
 	kgsl_events_init();
 
 	result = kgsl_cmdbatch_init();

drivers/gpu/msm/kgsl.h

diff --git a/drivers/gpu/msm/kgsl.h b/drivers/gpu/msm/kgsl.h
index 90dc550..8460476 100644
--- a/drivers/gpu/msm/kgsl.h
+++ b/drivers/gpu/msm/kgsl.h
@@ -26,6 +26,7 @@
 #include <linux/mm.h>
 #include <linux/dma-attrs.h>
 #include <linux/uaccess.h>
+#include <linux/kthread.h>
 #include <asm/cacheflush.h>
 
 /* The number of memstore arrays limits the number of contexts allowed.
@@ -132,6 +133,8 @@
 	unsigned int full_cache_threshold;
 	struct workqueue_struct *workqueue;
 	struct workqueue_struct *mem_workqueue;
+	struct kthread_worker worker;
+	struct task_struct *worker_thread;
 };
 
 extern struct kgsl_driver kgsl_driver;
@@ -273,7 +276,7 @@
 	void *priv;
 	struct list_head node;
 	unsigned int created;
-	struct work_struct work;
+	struct kthread_work work;
 	int result;
 	struct kgsl_event_group *group;
 };

drivers/gpu/msm/kgsl_events.c

diff --git a/drivers/gpu/msm/kgsl_events.c b/drivers/gpu/msm/kgsl_events.c
index 6e8abf3..859511b 100644
--- a/drivers/gpu/msm/kgsl_events.c
+++ b/drivers/gpu/msm/kgsl_events.c
@@ -32,7 +32,7 @@
 {
 	list_del(&event->node);
 	event->result = result;
-	queue_work(device->events_wq, &event->work);
+	queue_kthread_work(&kgsl_driver.worker, &event->work);
 }
 
 /**
@@ -42,7 +42,7 @@
  * Each event callback has its own work struct and is run on a event specific
  * workqeuue.  This is the worker that queues up the event callback function.
  */
-static void _kgsl_event_worker(struct work_struct *work)
+static void _kgsl_event_worker(struct kthread_work *work)
 {
 	struct kgsl_event *event = container_of(work, struct kgsl_event, work);
 	int id = KGSL_CONTEXT_ID(event->context);
@@ -282,7 +282,7 @@
 	event->created = jiffies;
 	event->group = group;
 
-	INIT_WORK(&event->work, _kgsl_event_worker);
+	init_kthread_work(&event->work, _kgsl_event_worker);
 
 	trace_kgsl_register_event(KGSL_CONTEXT_ID(context), timestamp, func);
 
@@ -297,7 +297,7 @@
 
 	if (timestamp_cmp(retired, timestamp) >= 0) {
 		event->result = KGSL_EVENT_RETIRED;
-		queue_work(device->events_wq, &event->work);
+		queue_kthread_work(&kgsl_driver.worker, &event->work);
 		spin_unlock(&group->lock);
 		return 0;
 	}