[PATCH] spi: use kthread_create_worker() helper

[PATCH] spi: use kthread_create_worker() helper

[Marek Szyprowski]

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@samsung.com>
---
 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

Re: [PATCH] spi: use kthread_create_worker() helper

[Mark Brown]

[-- Attachment #1: Type: text/plain, Size: 1082 bytes --]

On Wed, Jul 08, 2020 at 09:09:00AM +0200, Marek Szyprowski wrote:

> ------------[ 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)

Please think hard before including complete backtraces in upstream
reports, they are very large and contain almost no useful information
relative to their size so often obscure the relevant content in your
message. If part of the backtrace is usefully illustrative (it often is
for search engines if nothing else) then it's usually better to pull out
the relevant sections.

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

Re: [PATCH] spi: use kthread_create_worker() helper

[Petr Mladek]

On Wed 2020-07-08 09:09:00, Marek Szyprowski wrote:
> Since commit 4977caef05aa ("kthread: work could not be queued when worker
> being destroyed")

This commit should disappear from linux-next soon. We did not expect
that it would cause these warnings. We first want to fix the callers
before we put it back.

> 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.

But the fix is great and makes sense on its own.

The use of kthread_create_worker() simplifies the code. It uses
the kthread worker API the right way. It will eventually allow
to remove the FIXME in kthread_worker_fn() and add more consistency
checks.

I would use the above reasoning instead of the backtrace in the commit
message. And feel free to use:

Reviewed-by: Petr Mladek <pmladek@suse.com>

Best Regards,
Petr Mladek

Re: [PATCH] spi: use kthread_create_worker() helper

[Mark Brown]

On Wed, 8 Jul 2020 09:09:00 +0200, Marek Szyprowski wrote:
> 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:
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-next

Thanks!

[1/1] spi: use kthread_create_worker() helper
      commit: 60a883d119ab9ef63f830c85bbd2f0e2e2314f4f

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark