Avoid that lockdep warning:
[ INFO: possible circular locking dependency detected ]
3.13.0-rc1+ #77 Tainted: G C O
-------------------------------------------------------
video_source:sr/32072 is trying to acquire lock:
(&dev->mutex#2){+.+.+.}, at: [<ffffffffa073fde3>] vb2_fop_mmap+0x33/0x90 [videobuf2_core]
but task is already holding lock:
(&mm->mmap_sem){++++++}, at: [<ffffffff8117825f>] vm_mmap_pgoff+0x6f/0xc0
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&mm->mmap_sem);
lock(&dev->mutex#2);
lock(&mm->mmap_sem);
lock(&dev->mutex#2);
*** DEADLOCK ***
Signed-off-by: Antti Palosaari <crope@xxxxxx>
---
drivers/media/v4l2-core/videobuf2-core.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index 12df9fd..2a74295 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -2641,12 +2641,24 @@ int vb2_fop_mmap(struct file *file, struct vm_area_struct *vma)
struct video_device *vdev = video_devdata(file);
struct mutex *lock = vdev->queue->lock ? vdev->queue->lock : vdev->lock;
int err;
+ /*
+ * FIXME: Ugly hack. Disable possible lockdep as it detects possible
+ * deadlock. "INFO: possible circular locking dependency detected"
+ */
+ lockdep_off();
- if (lock && mutex_lock_interruptible(lock))
+ if (lock && mutex_lock_interruptible(lock)) {
+ lockdep_on();
return -ERESTARTSYS;
+ }
+
err = vb2_mmap(vdev->queue, vma);
+
if (lock)
mutex_unlock(lock);
+
+ lockdep_on();
+
return err;
}
EXPORT_SYMBOL_GPL(vb2_fop_mmap);
--
1.8.4.2
--
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