On Wed, Nov 06, 2019 at 08:52:58AM +0000, Chris Wilson wrote:
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@xxxxxxxxx>
>> Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@xxxxxxxxx>
>> ---
>> 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.
I am seeing,
CHECK drivers/gpu/drm/i915/gem/i915_gem_context.c
drivers/gpu/drm/i915/gem/i915_gem_context.c:1009:29: warning: incorrect type in argument 1 (different address spaces)
drivers/gpu/drm/i915/gem/i915_gem_context.c:1009:29: expected struct i915_address_space *vm
drivers/gpu/drm/i915/gem/i915_gem_context.c:1009:29: got struct i915_address_space [noderef] <asn:4> *vm
drivers/gpu/drm/i915/gem/i915_gem_context.c:1958:25: warning: incorrect type in argument 1 (different address spaces)
drivers/gpu/drm/i915/gem/i915_gem_context.c:1958:25: expected struct i915_gem_engines *e
drivers/gpu/drm/i915/gem/i915_gem_context.c:1958:25: got struct i915_gem_engines [noderef] <asn:4> *engines
drivers/gpu/drm/i915/gem/i915_gem_context.c:1993:15: warning: incorrect type in assignment (different address spaces)
drivers/gpu/drm/i915/gem/i915_gem_context.c:1993:15: expected struct i915_gem_engines *clone
drivers/gpu/drm/i915/gem/i915_gem_context.c:1993:15: got struct i915_gem_engines [noderef] <asn:4> *engines
Sure, for correctness see clone_vm().
Ok, I can put a common helper function like vm_get_rcu_safe(ctx).
Niranjana
-Chris
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