Re: [PATCH 3/3] drm/i915: Use rcu_dereference for rcu protected pointer

Re: [PATCH 3/3] drm/i915: Use rcu_dereference for rcu protected pointer

[Chris Wilson]

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@intel.com>
> Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@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.
-Chris
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Re: [Intel-gfx] [PATCH 3/3] drm/i915: Use rcu_dereference for rcu protected pointer

[Chris Wilson]

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@intel.com>
> Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@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.
-Chris
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Re: [PATCH 2/3] drm/i915: Check for ips_mchdev being NULL

[Chris Wilson]

Quoting Niranjana Vishwanathapura (2019-11-06 00:02:04)
> Guard against uninitalized (NULL) ips_mchdev before
> dereferencing.

Because?
-Chris
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Re: [Intel-gfx] [PATCH 2/3] drm/i915: Check for ips_mchdev being NULL

[Chris Wilson]

Quoting Niranjana Vishwanathapura (2019-11-06 00:02:04)
> Guard against uninitalized (NULL) ips_mchdev before
> dereferencing.

Because?
-Chris
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Re: [PATCH 1/3] drm/i915: Remove unwanted rcu_read_lock/unlock

[Chris Wilson]

Quoting Niranjana Vishwanathapura (2019-11-06 00:02:03)
> We don't need rcu read side critical section to call pid_nr(),
> remove it.
> 
> Cc: Chris P Wilson <chris.p.wilson@intel.com>
> Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_gpu_error.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
> index e8b67f5e521d..1f2f266f26af 100644
> --- a/drivers/gpu/drm/i915/i915_gpu_error.c
> +++ b/drivers/gpu/drm/i915/i915_gpu_error.c
> @@ -1230,10 +1230,7 @@ static void record_request(const struct i915_request *request,
>         erq->start = i915_ggtt_offset(request->ring->vma);
>         erq->head = request->head;
>         erq->tail = request->tail;
> -
> -       rcu_read_lock();
>         erq->pid = ctx->pid ? pid_nr(ctx->pid) : 0;
> -       rcu_read_unlock();

Ok, that was just cut'n'paste from pid_task()
Reviewed-by: Chris Wilson <chris.p.wilson@intel.com>
-Chris
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Re: [Intel-gfx] [PATCH 1/3] drm/i915: Remove unwanted rcu_read_lock/unlock

[Chris Wilson]

Quoting Niranjana Vishwanathapura (2019-11-06 00:02:03)
> We don't need rcu read side critical section to call pid_nr(),
> remove it.
> 
> Cc: Chris P Wilson <chris.p.wilson@intel.com>
> Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_gpu_error.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
> index e8b67f5e521d..1f2f266f26af 100644
> --- a/drivers/gpu/drm/i915/i915_gpu_error.c
> +++ b/drivers/gpu/drm/i915/i915_gpu_error.c
> @@ -1230,10 +1230,7 @@ static void record_request(const struct i915_request *request,
>         erq->start = i915_ggtt_offset(request->ring->vma);
>         erq->head = request->head;
>         erq->tail = request->tail;
> -
> -       rcu_read_lock();
>         erq->pid = ctx->pid ? pid_nr(ctx->pid) : 0;
> -       rcu_read_unlock();

Ok, that was just cut'n'paste from pid_task()
Reviewed-by: Chris Wilson <chris.p.wilson@intel.com>
-Chris
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Re: [PATCH 2/3] drm/i915: Check for ips_mchdev being NULL

[Niranjan Vishwanathapura]

On Wed, Nov 06, 2019 at 12:37:14AM +0000, Chris Wilson wrote:
>Quoting Niranjana Vishwanathapura (2019-11-06 00:02:04)
>> Guard against uninitalized (NULL) ips_mchdev before
>> dereferencing.
>
>Because?

I am seeing some exported functions like i915_read_mch_val() that try to
dereference ips_mchdev via mchdev_get(). I don't know full usage here,
but probably make these APIs fail safe?

Niranjana

>-Chris
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Re: [Intel-gfx] [PATCH 2/3] drm/i915: Check for ips_mchdev being NULL

[Niranjan Vishwanathapura]

On Wed, Nov 06, 2019 at 12:37:14AM +0000, Chris Wilson wrote:
>Quoting Niranjana Vishwanathapura (2019-11-06 00:02:04)
>> Guard against uninitalized (NULL) ips_mchdev before
>> dereferencing.
>
>Because?

I am seeing some exported functions like i915_read_mch_val() that try to
dereference ips_mchdev via mchdev_get(). I don't know full usage here,
but probably make these APIs fail safe?

Niranjana

>-Chris
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Re: [PATCH 3/3] drm/i915: Use rcu_dereference for rcu protected pointer

[Niranjan Vishwanathapura]

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@intel.com>
>> Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@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?

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

[Niranjan Vishwanathapura]

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@intel.com>
>> Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@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?

>-Chris
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Re: [PATCH 2/3] drm/i915: Check for ips_mchdev being NULL

[Chris Wilson]

Quoting Niranjan Vishwanathapura (2019-11-06 02:14:45)
> On Wed, Nov 06, 2019 at 12:37:14AM +0000, Chris Wilson wrote:
> >Quoting Niranjana Vishwanathapura (2019-11-06 00:02:04)
> >> Guard against uninitalized (NULL) ips_mchdev before
> >> dereferencing.
> >
> >Because?
> 
> I am seeing some exported functions like i915_read_mch_val() that try to
> dereference ips_mchdev via mchdev_get(). I don't know full usage here,
> but probably make these APIs fail safe?

Are you also going to make those functions safe when the module isn't
there? If that module interface is used outside of the registration
period, then the binding with the caller went horribly astray.
-Chris
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Re: [Intel-gfx] [PATCH 2/3] drm/i915: Check for ips_mchdev being NULL

[Chris Wilson]

Quoting Niranjan Vishwanathapura (2019-11-06 02:14:45)
> On Wed, Nov 06, 2019 at 12:37:14AM +0000, Chris Wilson wrote:
> >Quoting Niranjana Vishwanathapura (2019-11-06 00:02:04)
> >> Guard against uninitalized (NULL) ips_mchdev before
> >> dereferencing.
> >
> >Because?
> 
> I am seeing some exported functions like i915_read_mch_val() that try to
> dereference ips_mchdev via mchdev_get(). I don't know full usage here,
> but probably make these APIs fail safe?

Are you also going to make those functions safe when the module isn't
there? If that module interface is used outside of the registration
period, then the binding with the caller went horribly astray.
-Chris
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Re: [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@intel.com>
> >> Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@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
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Re: [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@intel.com>
> >> Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@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
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Re: [PATCH 3/3] drm/i915: Use rcu_dereference for rcu protected pointer

[Niranjan Vishwanathapura]

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@intel.com>
>> >> Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@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.

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

[Niranjan Vishwanathapura]

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@intel.com>
>> >> Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@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.

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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Re: [PATCH 3/3] drm/i915: Use rcu_dereference for rcu protected pointer

[Chris Wilson]

Quoting Niranjan Vishwanathapura (2019-11-07 05:05:26)
> On Wed, Nov 06, 2019 at 08:52:58AM +0000, Chris Wilson wrote:
> >Sure, for correctness see clone_vm().
> 
> Ok, I can put a common helper function like vm_get_rcu_safe(ctx).

https://patchwork.freedesktop.org/patch/339110/?series=69044&rev=1
-Chris
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Re: [Intel-gfx] [PATCH 3/3] drm/i915: Use rcu_dereference for rcu protected pointer

[Chris Wilson]

Quoting Niranjan Vishwanathapura (2019-11-07 05:05:26)
> On Wed, Nov 06, 2019 at 08:52:58AM +0000, Chris Wilson wrote:
> >Sure, for correctness see clone_vm().
> 
> Ok, I can put a common helper function like vm_get_rcu_safe(ctx).

https://patchwork.freedesktop.org/patch/339110/?series=69044&rev=1
-Chris
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