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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: Mikulas 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: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
This commit is contained in:
Mikulas Patocka 2019-04-01 17:46:56 +02:00 committed by Bartlomiej Zolnierkiewicz
parent bd86b6c5c6
commit 6b11f9d843
2 changed files with 59 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

56
drivers/video/fbdev/udlfb.c
View File

@ -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)) {

6
include/video/udlfb.h
View File

@ -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 */