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/pxafb.c b/drivers/video/pxafb.c
index 0889d50..6506117 100644
--- a/drivers/video/pxafb.c
+++ b/drivers/video/pxafb.c
@@ -815,8 +815,10 @@
ofb->video_mem_phys = virt_to_phys(ofb->video_mem);
ofb->video_mem_size = size;
+ mutex_lock(&ofb->fb.mm_lock);
ofb->fb.fix.smem_start = ofb->video_mem_phys;
ofb->fb.fix.smem_len = ofb->fb.fix.line_length * var->yres_virtual;
+ mutex_unlock(&ofb->fb.mm_lock);
ofb->fb.screen_base = ofb->video_mem;
return 0;
}