Commit 6b11f9d8 authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Bartlomiej Zolnierkiewicz
Browse files

udlfb: fix sleeping inside spinlock 



If a framebuffer device is used as a console, the rendering calls
(copyarea, fillrect, imageblit) may be done with the console spinlock
held. On udlfb, these function call dlfb_handle_damage that takes a
blocking semaphore before acquiring an URB.

In order to fix the bug, this patch changes the calls copyarea, fillrect
and imageblit to offload USB work to a workqueue.

A side effect of this patch is 3x improvement in console scrolling speed
because the device doesn't have to be updated after each copyarea call.

Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Cc: Bernie Thompson <bernie@plugable.com>
Cc: Ladislav Michl <ladis@linux-mips.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarBartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
parent bd86b6c5

drivers/video/fbdev/udlfb.c

+53 −3
Original line number Diff line number Diff line
@@ -657,6 +657,50 @@ error: 
	return 0;

}



static void dlfb_init_damage(struct dlfb_data *dlfb)

{

	dlfb->damage_x = INT_MAX;

	dlfb->damage_x2 = 0;

	dlfb->damage_y = INT_MAX;

	dlfb->damage_y2 = 0;

}



static void dlfb_damage_work(struct work_struct *w)

{

	struct dlfb_data *dlfb = container_of(w, struct dlfb_data, damage_work);

	int x, x2, y, y2;



	spin_lock_irq(&dlfb->damage_lock);

	x = dlfb->damage_x;

	x2 = dlfb->damage_x2;

	y = dlfb->damage_y;

	y2 = dlfb->damage_y2;

	dlfb_init_damage(dlfb);

	spin_unlock_irq(&dlfb->damage_lock);



	if (x < x2 && y < y2)

		dlfb_handle_damage(dlfb, x, y, x2 - x, y2 - y);

}



static void dlfb_offload_damage(struct dlfb_data *dlfb, int x, int y, int width, int height)

{

	unsigned long flags;

	int x2 = x + width;

	int y2 = y + height;



	if (x >= x2 || y >= y2)

		return;



	spin_lock_irqsave(&dlfb->damage_lock, flags);

	dlfb->damage_x = min(x, dlfb->damage_x);

	dlfb->damage_x2 = max(x2, dlfb->damage_x2);

	dlfb->damage_y = min(y, dlfb->damage_y);

	dlfb->damage_y2 = max(y2, dlfb->damage_y2);

	spin_unlock_irqrestore(&dlfb->damage_lock, flags);



	schedule_work(&dlfb->damage_work);

}



/*

 * Path triggered by usermode clients who write to filesystem

 * e.g. cat filename > /dev/fb1
@@ -693,7 +737,7 @@ static void dlfb_ops_copyarea(struct fb_info *info, 


	sys_copyarea(info, area);



	dlfb_handle_damage(dlfb, area->dx, area->dy,

	dlfb_offload_damage(dlfb, area->dx, area->dy,

			area->width, area->height);

}
@@ -704,7 +748,7 @@ static void dlfb_ops_imageblit(struct fb_info *info, 


	sys_imageblit(info, image);



	dlfb_handle_damage(dlfb, image->dx, image->dy,

	dlfb_offload_damage(dlfb, image->dx, image->dy,

			image->width, image->height);

}
@@ -715,7 +759,7 @@ static void dlfb_ops_fillrect(struct fb_info *info, 


	sys_fillrect(info, rect);



	dlfb_handle_damage(dlfb, rect->dx, rect->dy, rect->width,

	dlfb_offload_damage(dlfb, rect->dx, rect->dy, rect->width,

			      rect->height);

}
@@ -940,6 +984,8 @@ static void dlfb_ops_destroy(struct fb_info *info) 
{

	struct dlfb_data *dlfb = info->par;



	cancel_work_sync(&dlfb->damage_work);



	if (info->cmap.len != 0)

		fb_dealloc_cmap(&info->cmap);

	if (info->monspecs.modedb)
@@ -1636,6 +1682,10 @@ static int dlfb_usb_probe(struct usb_interface *intf, 
	dlfb->ops = dlfb_ops;

	info->fbops = &dlfb->ops;



	dlfb_init_damage(dlfb);

	spin_lock_init(&dlfb->damage_lock);

	INIT_WORK(&dlfb->damage_work, dlfb_damage_work);



	INIT_LIST_HEAD(&info->modelist);



	if (!dlfb_alloc_urb_list(dlfb, WRITES_IN_FLIGHT, MAX_TRANSFER)) {

include/video/udlfb.h

+6 −0
Original line number Diff line number Diff line
@@ -48,6 +48,12 @@ struct dlfb_data { 
	int base8;

	u32 pseudo_palette[256];

	int blank_mode; /*one of FB_BLANK_ */

	int damage_x;

	int damage_y;

	int damage_x2;

	int damage_y2;

	spinlock_t damage_lock;

	struct work_struct damage_work;

	struct fb_ops ops;

	/* blit-only rendering path metrics, exposed through sysfs */

	atomic_t bytes_rendered; /* raw pixel-bytes driver asked to render */

CRA Git | Maintained and supported by SUSTech CRA and CCSE