[PATCH] spi: use kthread_create_worker() helper

[Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>]

Since commit 4977caef05aa ("kthread: work could not be queued when worker
being destroyed") there is a warning when kworker is used without the
internal 'task' entry properly initialized. Fix this by using
a kthread_create_worker() helper instead of open-coding a kworker
initialization.

This fixes a following warning during SPI controller probe, observed on
the Samsung Exynos 5420-based Peach-Pit Chromebook with recent linux-next
kernel:

------------[ cut here ]------------
WARNING: CPU: 3 PID: 1 at kernel/kthread.c:817 kthread_queue_work+0xac/0xd4
Modules linked in:
CPU: 3 PID: 1 Comm: swapper/0 Not tainted 5.8.0-rc4-00017-g4977caef05aa #1193
Hardware name: Samsung Exynos (Flattened Device Tree)
[<c011184c>] (unwind_backtrace) from [<c010d250>] (show_stack+0x10/0x14)
[<c010d250>] (show_stack) from [<c0517f64>] (dump_stack+0xbc/0xe8)
[<c0517f64>] (dump_stack) from [<c01270a8>] (__warn+0xf0/0x108)
[<c01270a8>] (__warn) from [<c0127170>] (warn_slowpath_fmt+0xb0/0xb8)
[<c0127170>] (warn_slowpath_fmt) from [<c01512a4>] (kthread_queue_work+0xac/0xd4)
[<c01512a4>] (kthread_queue_work) from [<c06c38d4>] (spi_start_queue+0x58/0x74)
[<c06c38d4>] (spi_start_queue) from [<c06c50d4>] (spi_register_controller+0x53c/0xbe8)
[<c06c50d4>] (spi_register_controller) from [<c06c57b4>] (devm_spi_register_controller+0x34/0x6c)
[<c06c57b4>] (devm_spi_register_controller) from [<c06cad60>] (s3c64xx_spi_probe+0x3e0/0x7ec)
[<c06cad60>] (s3c64xx_spi_probe) from [<c064dc8c>] (platform_drv_probe+0x6c/0xa4)
[<c064dc8c>] (platform_drv_probe) from [<c064b2c0>] (really_probe+0x200/0x48c)
[<c064b2c0>] (really_probe) from [<c064b6b4>] (driver_probe_device+0x78/0x1fc)
[<c064b6b4>] (driver_probe_device) from [<c064ba9c>] (device_driver_attach+0x58/0x60)
[<c064ba9c>] (device_driver_attach) from [<c064bb80>] (__driver_attach+0xdc/0x174)
[<c064bb80>] (__driver_attach) from [<c06490cc>] (bus_for_each_dev+0x68/0xb4)
[<c06490cc>] (bus_for_each_dev) from [<c064a400>] (bus_add_driver+0x158/0x214)
[<c064a400>] (bus_add_driver) from [<c064ca54>] (driver_register+0x78/0x110)
[<c064ca54>] (driver_register) from [<c0102378>] (do_one_initcall+0x8c/0x424)
[<c0102378>] (do_one_initcall) from [<c1001158>] (kernel_init_freeable+0x190/0x204)
[<c1001158>] (kernel_init_freeable) from [<c0ab6d44>] (kernel_init+0x8/0x118)
[<c0ab6d44>] (kernel_init) from [<c0100114>] (ret_from_fork+0x14/0x20)
Exception stack(0xedd01fb0 to 0xedd01ff8)
...
irq event stamp: 173882
hardirqs last  enabled at (173881): [<c0abf294>] _raw_spin_unlock_irqrestore+0x68/0x70
hardirqs last disabled at (173882): [<c0abece0>] _raw_spin_lock_irqsave+0x1c/0x58
softirqs last  enabled at (171200): [<c027240c>] bdi_register_va+0x178/0x2fc
softirqs last disabled at (171198): [<c027239c>] bdi_register_va+0x108/0x2fc
---[ end trace 0fe37f6a9b7e6bc7 ]---

Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
---
 drivers/spi/spi.c       | 26 ++++++++++++--------------
 include/linux/spi/spi.h |  6 ++----
 2 files changed, 14 insertions(+), 18 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 805a51b6f54c..19a03a8d6199 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1368,7 +1368,7 @@ static void __spi_pump_messages(struct spi_controller *ctlr, bool in_kthread)
 
 	/* If another context is idling the device then defer */
 	if (ctlr->idling) {
-		kthread_queue_work(&ctlr->kworker, &ctlr->pump_messages);
+		kthread_queue_work(ctlr->kworker, &ctlr->pump_messages);
 		spin_unlock_irqrestore(&ctlr->queue_lock, flags);
 		return;
 	}
@@ -1382,7 +1382,7 @@ static void __spi_pump_messages(struct spi_controller *ctlr, bool in_kthread)
 
 		/* Only do teardown in the thread */
 		if (!in_kthread) {
-			kthread_queue_work(&ctlr->kworker,
+			kthread_queue_work(ctlr->kworker,
 					   &ctlr->pump_messages);
 			spin_unlock_irqrestore(&ctlr->queue_lock, flags);
 			return;
@@ -1616,7 +1616,7 @@ static void spi_set_thread_rt(struct spi_controller *ctlr)
 {
 	dev_info(&ctlr->dev,
 		"will run message pump with realtime priority\n");
-	sched_set_fifo(ctlr->kworker_task);
+	sched_set_fifo(ctlr->kworker->task);
 }
 
 static int spi_init_queue(struct spi_controller *ctlr)
@@ -1624,13 +1624,12 @@ static int spi_init_queue(struct spi_controller *ctlr)
 	ctlr->running = false;
 	ctlr->busy = false;
 
-	kthread_init_worker(&ctlr->kworker);
-	ctlr->kworker_task = kthread_run(kthread_worker_fn, &ctlr->kworker,
-					 "%s", dev_name(&ctlr->dev));
-	if (IS_ERR(ctlr->kworker_task)) {
-		dev_err(&ctlr->dev, "failed to create message pump task\n");
-		return PTR_ERR(ctlr->kworker_task);
+	ctlr->kworker = kthread_create_worker(0, dev_name(&ctlr->dev));
+	if (IS_ERR(ctlr->kworker)) {
+		dev_err(&ctlr->dev, "failed to create message pump kworker\n");
+		return PTR_ERR(ctlr->kworker);
 	}
+
 	kthread_init_work(&ctlr->pump_messages, spi_pump_messages);
 
 	/*
@@ -1714,7 +1713,7 @@ void spi_finalize_current_message(struct spi_controller *ctlr)
 	ctlr->cur_msg = NULL;
 	ctlr->cur_msg_prepared = false;
 	ctlr->fallback = false;
-	kthread_queue_work(&ctlr->kworker, &ctlr->pump_messages);
+	kthread_queue_work(ctlr->kworker, &ctlr->pump_messages);
 	spin_unlock_irqrestore(&ctlr->queue_lock, flags);
 
 	trace_spi_message_done(mesg);
@@ -1740,7 +1739,7 @@ static int spi_start_queue(struct spi_controller *ctlr)
 	ctlr->cur_msg = NULL;
 	spin_unlock_irqrestore(&ctlr->queue_lock, flags);
 
-	kthread_queue_work(&ctlr->kworker, &ctlr->pump_messages);
+	kthread_queue_work(ctlr->kworker, &ctlr->pump_messages);
 
 	return 0;
 }
@@ -1796,8 +1795,7 @@ static int spi_destroy_queue(struct spi_controller *ctlr)
 		return ret;
 	}
 
-	kthread_flush_worker(&ctlr->kworker);
-	kthread_stop(ctlr->kworker_task);
+	kthread_destroy_worker(ctlr->kworker);
 
 	return 0;
 }
@@ -1820,7 +1818,7 @@ static int __spi_queued_transfer(struct spi_device *spi,
 
 	list_add_tail(&msg->queue, &ctlr->queue);
 	if (!ctlr->busy && need_pump)
-		kthread_queue_work(&ctlr->kworker, &ctlr->pump_messages);
+		kthread_queue_work(ctlr->kworker, &ctlr->pump_messages);
 
 	spin_unlock_irqrestore(&ctlr->queue_lock, flags);
 	return 0;
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 0e67a9a3a1d3..5fcf5da13fdb 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -358,8 +358,7 @@ static inline void spi_unregister_driver(struct spi_driver *sdrv)
  * @cleanup: frees controller-specific state
  * @can_dma: determine whether this controller supports DMA
  * @queued: whether this controller is providing an internal message queue
- * @kworker: thread struct for message pump
- * @kworker_task: pointer to task for message pump kworker thread
+ * @kworker: pointer to thread struct for message pump
  * @pump_messages: work struct for scheduling work to the message pump
  * @queue_lock: spinlock to syncronise access to message queue
  * @queue: message queue
@@ -593,8 +592,7 @@ struct spi_controller {
 	 * Over time we expect SPI drivers to be phased over to this API.
 	 */
 	bool				queued;
-	struct kthread_worker		kworker;
-	struct task_struct		*kworker_task;
+	struct kthread_worker		*kworker;
 	struct kthread_work		pump_messages;
 	spinlock_t			queue_lock;
 	struct list_head		queue;
-- 
2.17.1