linux-kernel - [PATCH] fb: udlfb: fix scheduling while atomic.

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Date:	Sat,  5 Jan 2013 12:42:09 +0100
From:	Alexander Holler <holler@...oftware.de>
To:	linux-kernel@...r.kernel.org
Cc:	linux-fbdev@...r.kernel.org, Bernie Thompson <bernie@...gable.com>,
	Florian Tobias Schandinat <FlorianSchandinat@....de>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Steve Glendinning <steve.glendinning@...well.net>,
	Dave Airlie <airlied@...hat.com>,
	Alexander Holler <holler@...oftware.de>,
	<stable@...r.kernel.org>
Subject: [PATCH] fb: udlfb: fix scheduling while atomic.

The console functions are using spinlocks while calling fb-driver ops
but udlfb waits for a semaphore in many ops. This results in the BUG
"scheduling while atomic". One of those call flows is e.g.

vt_console_print() (spinlock printing_lock)
	(...)
	dlfb_ops_imageblit()
                        dlfb_handle_damage()
                                dlfb_get_urb()
					down_timeout(semaphore)
BUG: scheduling while atomic
(...)
vt_console_print() (release spinlock printing_lock)

Fix this through a workqueue for dlfb_handle_damage().

Cc: <stable@...r.kernel.org>
Signed-off-by: Alexander Holler <holler@...oftware.de>
---
 drivers/video/udlfb.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 51 insertions(+), 2 deletions(-)

diff --git a/drivers/video/udlfb.c b/drivers/video/udlfb.c
index 86d449e..5aadcb2 100644
--- a/drivers/video/udlfb.c
+++ b/drivers/video/udlfb.c
@@ -569,7 +569,7 @@ static int dlfb_render_hline(struct dlfb_data *dev, struct urb **urb_ptr,
 	return 0;
 }
 
-int dlfb_handle_damage(struct dlfb_data *dev, int x, int y,
+int dlfb_handle_damage_queued(struct dlfb_data *dev, int x, int y,
 	       int width, int height, char *data)
 {
 	int i, ret;
@@ -630,6 +630,44 @@ error:
 	return 0;
 }
 
+static struct workqueue_struct *dlfb_handle_damage_wq;
+
+struct dlfb_handle_damage_work {
+	struct work_struct my_work;
+	struct dlfb_data *dev;
+	char *data;
+	int x, y, width, height;
+};
+
+static void dlfb_handle_damage_work(struct work_struct *work)
+{
+	struct dlfb_handle_damage_work *my_work =
+		(struct dlfb_handle_damage_work *)work;
+
+	dlfb_handle_damage_queued(my_work->dev, my_work->x, my_work->y,
+			my_work->width, my_work->height, my_work->data);
+	kfree(work);
+	return;
+}
+
+void dlfb_handle_damage(struct dlfb_data *dev, int x, int y,
+	       int width, int height, char *data)
+{
+	struct dlfb_handle_damage_work *work =
+		kmalloc(sizeof(struct dlfb_handle_damage_work), GFP_KERNEL);
+
+	if (work) {
+		INIT_WORK((struct work_struct *)work, dlfb_handle_damage_work);
+		work->dev = dev;
+		work->x = x;
+		work->y = y;
+		work->width = width;
+		work->height = height;
+		work->data = data;
+		queue_work(dlfb_handle_damage_wq, (struct work_struct *)work);
+	}
+}
+
 /*
  * Path triggered by usermode clients who write to filesystem
  * e.g. cat filename > /dev/fb1
@@ -945,6 +983,9 @@ static void dlfb_free_framebuffer(struct dlfb_data *dev)
 
 		unregister_framebuffer(info);
 
+		if (dlfb_handle_damage_wq)
+			destroy_workqueue(dlfb_handle_damage_wq);
+
 		if (info->cmap.len != 0)
 			fb_dealloc_cmap(&info->cmap);
 		if (info->monspecs.modedb)
@@ -1626,13 +1667,13 @@ static int dlfb_usb_probe(struct usb_interface *interface,
 		dev->sku_pixel_limit = pixel_limit;
 	}
 
-
 	if (!dlfb_alloc_urb_list(dev, WRITES_IN_FLIGHT, MAX_TRANSFER)) {
 		retval = -ENOMEM;
 		pr_err("dlfb_alloc_urb_list failed\n");
 		goto error;
 	}
 
+
 	kref_get(&dev->kref); /* matching kref_put in free_framebuffer_work */
 
 	/* We don't register a new USB class. Our client interface is fbdev */
@@ -1694,6 +1735,13 @@ static void dlfb_init_framebuffer_work(struct work_struct *work)
 		goto error;
 	}
 
+	dlfb_handle_damage_wq = alloc_workqueue("udlfb_damage",
+						WQ_MEM_RECLAIM, 0);
+	if (dlfb_handle_damage_wq == NULL) {
+		pr_err("unable to allocate workqueue\n");
+		goto error;
+	}
+
 	/* ready to begin using device */
 
 	atomic_set(&dev->usb_active, 1);
@@ -1702,6 +1750,7 @@ static void dlfb_init_framebuffer_work(struct work_struct *work)
 	dlfb_ops_check_var(&info->var, info);
 	dlfb_ops_set_par(info);
 
+
 	retval = register_framebuffer(info);
 	if (retval < 0) {
 		pr_err("register_framebuffer failed %d\n", retval);
-- 
1.7.11.7

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