[PATCH] drm/gem: add mutex lock when using drm_gem_mmap_obj

[YoungJun Cho]

On Jun 26, 2013 4:13 PM, "Maarten Lankhorst" <
maarten.lankhorst at canonical.com> wrote:
>
> Op 26-06-13 04:14, Seung-Woo Kim schreef:
> > From: YoungJun Cho <yj44.cho at samsung.com>
> >
> > The drm_gem_mmap_obj() has to be protected with dev->struct_mutex,
> > but some caller functions do not. So it adds mutex lock to missing
> > callers and adds WARN_ON assertion whether drm_gem_mmap_obj() is
> > called with mutex lock or not.
> >
> > Signed-off-by: YoungJun Cho <yj44.cho at samsung.com>
> > Signed-off-by: Seung-Woo Kim <sw0312.kim at samsung.com>
> > Signed-off-by: Kyungmin Park <kyungmin.park at samsung.com>
> > CC: Laurent Pinchart <laurent.pinchart+renesas at ideasonboard.com>
> > CC: Rob Clark <robdclark at gmail.com>
> > ---
> > This patch is based on drm-next branch.
> >
> >  drivers/gpu/drm/drm_gem.c                 |    4 ++++
> >  drivers/gpu/drm/drm_gem_cma_helper.c      |    3 +++
> >  drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c |    3 +++
> >  3 files changed, 10 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> > index 4321713..b19bba0 100644
> > --- a/drivers/gpu/drm/drm_gem.c
> > +++ b/drivers/gpu/drm/drm_gem.c
> > @@ -661,6 +661,8 @@ EXPORT_SYMBOL(drm_gem_vm_close);
> >   * the GEM object is not looked up based on its fake offset. To
implement the
> >   * DRM mmap operation, drivers should use the drm_gem_mmap() function.
> >   *
> > + * NOTE: This function has to be protected with dev->struct_mutex
> > + *
> >   * Return 0 or success or -EINVAL if the object size is smaller than
the VMA
> >   * size, or if no gem_vm_ops are provided.
> >   */
> > @@ -669,6 +671,8 @@ int drm_gem_mmap_obj(struct drm_gem_object *obj,
unsigned long obj_size,
> >  {
> >       struct drm_device *dev = obj->dev;
> >
> > +     WARN_ON(!mutex_is_locked(&dev->struct_mutex));
> >
> Please don't use mutex_is_locked, use lockdep_assert_held, so the cost
only exists when PROVE_LOCKING is used..
>
> I know some current code does it wrong, but that is the correct function
to use.
>
> ~Maarten
>

Thank you for nice comments!
I will update it again.

Best regards YJ
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