fbdev: add mutex for fb_mmap locking
Add a mutex to avoid a circular locking problem between the mm layer
semaphore and fbdev ioctl mutex through the fb_mmap() call.
Also, add mutex to all places where smem_start and smem_len fields change
so the mutex inside the fb_mmap() is actually used. Changing of these
fields before calling the framebuffer_register() are not mutexed.
This is 2.6.31 material. It removes one lockdep (fb_mmap() and
register_framebuffer()) but there is still another one (fb_release() and
register_framebuffer()). It also cleans up handling of the smem_start and
smem_len fields used by mutexed section of the fb_mmap().
Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/video/sm501fb.c b/drivers/video/sm501fb.c
index eb5d73a..98f24f0 100644
--- a/drivers/video/sm501fb.c
+++ b/drivers/video/sm501fb.c
@@ -145,7 +145,7 @@
#define SM501_MEMF_ACCEL (8)
static int sm501_alloc_mem(struct sm501fb_info *inf, struct sm501_mem *mem,
- unsigned int why, size_t size)
+ unsigned int why, size_t size, u32 smem_len)
{
struct sm501fb_par *par;
struct fb_info *fbi;
@@ -172,7 +172,7 @@
if (ptr > 0)
ptr &= ~(PAGE_SIZE - 1);
- if (fbi && ptr < fbi->fix.smem_len)
+ if (fbi && ptr < smem_len)
return -ENOMEM;
break;
@@ -197,7 +197,7 @@
case SM501_MEMF_ACCEL:
fbi = inf->fb[HEAD_CRT];
- ptr = fbi ? fbi->fix.smem_len : 0;
+ ptr = fbi ? smem_len : 0;
fbi = inf->fb[HEAD_PANEL];
if (fbi) {
@@ -413,6 +413,7 @@
unsigned int mem_type;
unsigned int clock_type;
unsigned int head_addr;
+ unsigned int smem_len;
dev_dbg(fbi->dev, "%s: %dx%d, bpp = %d, virtual %dx%d\n",
__func__, var->xres, var->yres, var->bits_per_pixel,
@@ -453,18 +454,20 @@
/* allocate fb memory within 501 */
info->fix.line_length = (var->xres_virtual * var->bits_per_pixel)/8;
- info->fix.smem_len = info->fix.line_length * var->yres_virtual;
+ smem_len = info->fix.line_length * var->yres_virtual;
dev_dbg(fbi->dev, "%s: line length = %u\n", __func__,
info->fix.line_length);
- if (sm501_alloc_mem(fbi, &par->screen, mem_type,
- info->fix.smem_len)) {
+ if (sm501_alloc_mem(fbi, &par->screen, mem_type, smem_len, smem_len)) {
dev_err(fbi->dev, "no memory available\n");
return -ENOMEM;
}
+ mutex_lock(&info->mm_lock);
info->fix.smem_start = fbi->fbmem_res->start + par->screen.sm_addr;
+ info->fix.smem_len = smem_len;
+ mutex_unlock(&info->mm_lock);
info->screen_base = fbi->fbmem + par->screen.sm_addr;
info->screen_size = info->fix.smem_len;
@@ -637,7 +640,8 @@
if ((control & SM501_DC_CRT_CONTROL_SEL) == 0) {
/* the head is displaying panel data... */
- sm501_alloc_mem(fbi, &par->screen, SM501_MEMF_CRT, 0);
+ sm501_alloc_mem(fbi, &par->screen, SM501_MEMF_CRT, 0,
+ info->fix.smem_len);
goto out_update;
}
@@ -1289,7 +1293,8 @@
par->cursor_regs = info->regs + reg_base;
- ret = sm501_alloc_mem(info, &par->cursor, SM501_MEMF_CURSOR, 1024);
+ ret = sm501_alloc_mem(info, &par->cursor, SM501_MEMF_CURSOR, 1024,
+ fbi->fix.smem_len);
if (ret < 0)
return ret;