[Intel-gfx] [PATCH 3/3] drm/i915: Use rcu_dereference for rcu protected pointer

[Chris Wilson]

Quoting Niranjan Vishwanathapura (2019-11-06 02:16:42)
> On Wed, Nov 06, 2019 at 12:36:47AM +0000, Chris Wilson wrote:
> >Quoting Niranjana Vishwanathapura (2019-11-06 00:02:05)
> >> 'ctx\->vm' is rcu protected, so use rcu_dereference inside
> >> read side critical section. It fixes a sparse warning.
> >>
> >> Cc: Chris P Wilson <chris.p.wilson at intel.com>
> >> Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura at intel.com>
> >> ---
> >>  drivers/gpu/drm/i915/gem/i915_gem_context.c | 9 +++++----
> >>  1 file changed, 5 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> >> index de6e55af82cf..d3a622f60fd9 100644
> >> --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> >> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> >> @@ -1002,12 +1002,13 @@ static int get_ppgtt(struct drm_i915_file_private *file_priv,
> >>         struct i915_address_space *vm;
> >>         int ret;
> >>
> >> -       if (!rcu_access_pointer(ctx->vm))
> >> -               return -ENODEV;
> >
> >This is correctly serialised by the caller.
> 
> Ok, is this worth fixing the sparse warning?

  CHECK   drivers/gpu/drm/i915/gem/i915_gem_context.c
drivers/gpu/drm/i915/gem/i915_gem_context.c:2087:17: error: bad integer constant expression
drivers/gpu/drm/i915/gem/i915_gem_context.c:2088:17: error: bad integer constant expression
drivers/gpu/drm/i915/gem/i915_gem_context.c:2089:17: error: bad integer constant expression
drivers/gpu/drm/i915/gem/i915_gem_context.c:2090:17: error: bad integer constant expression
drivers/gpu/drm/i915/gem/i915_gem_context.c:2091:17: error: bad integer constant expression
drivers/gpu/drm/i915/gem/i915_gem_context.c:2092:17: error: bad integer constant expression

Odd.

Sure, for correctness see clone_vm().
-Chris