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/fsl-diu-fb.c b/drivers/video/fsl-diu-fb.c
index f153c58..0bf2190 100644
--- a/drivers/video/fsl-diu-fb.c
+++ b/drivers/video/fsl-diu-fb.c
@@ -750,24 +750,26 @@
static int map_video_memory(struct fb_info *info)
{
phys_addr_t phys;
+ u32 smem_len = info->fix.line_length * info->var.yres_virtual;
pr_debug("info->var.xres_virtual = %d\n", info->var.xres_virtual);
pr_debug("info->var.yres_virtual = %d\n", info->var.yres_virtual);
pr_debug("info->fix.line_length = %d\n", info->fix.line_length);
+ pr_debug("MAP_VIDEO_MEMORY: smem_len = %u\n", smem_len);
- info->fix.smem_len = info->fix.line_length * info->var.yres_virtual;
- pr_debug("MAP_VIDEO_MEMORY: smem_len = %d\n", info->fix.smem_len);
- info->screen_base = fsl_diu_alloc(info->fix.smem_len, &phys);
+ info->screen_base = fsl_diu_alloc(smem_len, &phys);
if (info->screen_base == NULL) {
printk(KERN_ERR "Unable to allocate fb memory\n");
return -ENOMEM;
}
+ mutex_lock(&info->mm_lock);
info->fix.smem_start = (unsigned long) phys;
+ info->fix.smem_len = smem_len;
+ mutex_unlock(&info->mm_lock);
info->screen_size = info->fix.smem_len;
pr_debug("Allocated fb @ paddr=0x%08lx, size=%d.\n",
- info->fix.smem_start,
- info->fix.smem_len);
+ info->fix.smem_start, info->fix.smem_len);
pr_debug("screen base %p\n", info->screen_base);
return 0;
@@ -776,9 +778,11 @@
static void unmap_video_memory(struct fb_info *info)
{
fsl_diu_free(info->screen_base, info->fix.smem_len);
+ mutex_lock(&info->mm_lock);
info->screen_base = NULL;
info->fix.smem_start = 0;
info->fix.smem_len = 0;
+ mutex_unlock(&info->mm_lock);
}
/*