Re: [Mesa-dev] [PATCH 1/6] gallium: clarify the constraints on sampler_view_destroy

2017-10-11 Thread Nicolai Hähnle 

On 11.10.2017 01:25, Gurchetan Singh wrote:
"The GL state tracker, which is the only one that runs into the 
multi-context subtleties (due to share groups), already guarantees that 
sampler views are destroyed before their context of creation is destroyed."


How does the GL state tracker guarantee this?  Does this guarantee also 
apply to pipe_surfaces?  Context: ChromiumOS previously ran into an 
issue where sampler_views and pipe_surfaces outlived the context that 
created them [1], and we have technical debt [2][3][4] emanating from 
this.  It would be great to remove this, if things have changed in the 
Gallium code.


st/mesa creates sampler views of two types:

1. There are sampler views associated to normal textures, which are 
created in st_sampler_view.c. Those sampler views are always created by 
the context that uses them; when the context is destroyed, they are all 
released (via st_destroy_context --> destroy_tex_sampler_cb).


2. Temporary sampler views are created in some places (e.g. for blits), 
but those are released immediately after setting them in the 
pipe_context via cso.


I'm not so sure about pipe_surface objects, nor about other state trackers.

Unfortunately, none of your links is particularly informative about the 
sequence of events that lead to whatever problems they were trying to fix :/


All I can say is that I've never seen a crash related to a sampler view 
being destroyed after its owning context with Mesa master, but I realize 
that may not be too helpful...


Cheers,
Nicolai




[1] 
https://lists.freedesktop.org/archives/mesa-dev/2011-September/011578.html
[2] 
https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/master/media-libs/mesa/files/10.3-state_tracker-gallium-fix-crash-with-st_renderbuffer.patch
[3] 
https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/master/media-libs/mesa/files/10.3-state_tracker-gallium-fix-crash-with-st_renderbuffer-freedreno.patch
[4] 
https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/master/media-libs/mesa/files/12.1-radeonsi-sampler_view_destroy.patch


On Tue, Oct 10, 2017 at 2:42 PM, Nicolai Hähnle > wrote:


Same as on IRC:

On 10.10.2017 04:06, Marek Olšák wrote:

Is there any difference with piglit/drawoverhead?


Yes, there is.


If yes, would this be useful?
https://patchwork.freedesktop.org/patch/41241/



Surprisingly, not that much. I'm going to think though a couple of
other options, but want to already push patch #3; I sent a version
that is rebased on master and disentangled from the locking stuff.

Cheers,
Nicolai



Marek


On Fri, Oct 6, 2017 at 10:38 PM, Nicolai Hähnle
> wrote:

From: Nicolai Hähnle >

r600 expects the context that created the sampler view to
still be alive
(there is a per-context list of sampler views).

svga currently bails when the context of destruction is not
the same as
creation.

The GL state tracker, which is the only one that runs into the
multi-context subtleties (due to share groups), already
guarantees that
sampler views are destroyed before their context of creation
is destroyed.

Most drivers are context-agnostic, so the warning message in
pipe_sampler_view_release doesn't really make sense.
---
   src/gallium/auxiliary/util/u_inlines.h   | 16
++--
   src/gallium/include/pipe/p_context.h     | 10 ++
   src/mesa/state_tracker/st_sampler_view.c |  1 -
   3 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/src/gallium/auxiliary/util/u_inlines.h
b/src/gallium/auxiliary/util/u_inlines.h
index 79f62c32266..790352d7800 100644
--- a/src/gallium/auxiliary/util/u_inlines.h
+++ b/src/gallium/auxiliary/util/u_inlines.h
@@ -142,45 +142,49 @@ pipe_resource_reference(struct
pipe_resource **ptr, struct pipe_resource *tex)
            struct pipe_resource *next = old_tex->next;

  
  old_tex->screen->resource_destroy(old_tex->screen, old_tex);

            old_tex = next;
         } while
(pipe_reference_described(_tex->reference, NULL,
  
(debug_reference_descriptor)debug_describe_resource));

      }
      *ptr = tex;
   }

+/**
+ * Set *ptr to \p view with proper reference counting.

Re: [Mesa-dev] [PATCH 1/6] gallium: clarify the constraints on sampler_view_destroy

2017-10-10 Thread Gurchetan Singh 
"The GL state tracker, which is the only one that runs into the
multi-context subtleties (due to share groups), already guarantees that
sampler views are destroyed before their context of creation is destroyed."

How does the GL state tracker guarantee this?  Does this guarantee also
apply to pipe_surfaces?  Context: ChromiumOS previously ran into an issue
where sampler_views and pipe_surfaces outlived the context that created
them [1], and we have technical debt [2][3][4] emanating from this.  It
would be great to remove this, if things have changed in the Gallium code.

[1]
https://lists.freedesktop.org/archives/mesa-dev/2011-September/011578.html
[2]
https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/master/media-libs/mesa/files/10.3-state_tracker-gallium-fix-crash-with-st_renderbuffer.patch
[3]
https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/master/media-libs/mesa/files/10.3-state_tracker-gallium-fix-crash-with-st_renderbuffer-freedreno.patch
[4]
https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/master/media-libs/mesa/files/12.1-radeonsi-sampler_view_destroy.patch

On Tue, Oct 10, 2017 at 2:42 PM, Nicolai Hähnle  wrote:

> Same as on IRC:
>
> On 10.10.2017 04:06, Marek Olšák wrote:
>
>> Is there any difference with piglit/drawoverhead?
>>
>
> Yes, there is.
>
>
> If yes, would this be useful?
>> https://patchwork.freedesktop.org/patch/41241/
>>
>
> Surprisingly, not that much. I'm going to think though a couple of other
> options, but want to already push patch #3; I sent a version that is
> rebased on master and disentangled from the locking stuff.
>
> Cheers,
> Nicolai
>
>
>
>> Marek
>>
>>
>> On Fri, Oct 6, 2017 at 10:38 PM, Nicolai Hähnle 
>> wrote:
>>
>>> From: Nicolai Hähnle 
>>>
>>> r600 expects the context that created the sampler view to still be alive
>>> (there is a per-context list of sampler views).
>>>
>>> svga currently bails when the context of destruction is not the same as
>>> creation.
>>>
>>> The GL state tracker, which is the only one that runs into the
>>> multi-context subtleties (due to share groups), already guarantees that
>>> sampler views are destroyed before their context of creation is
>>> destroyed.
>>>
>>> Most drivers are context-agnostic, so the warning message in
>>> pipe_sampler_view_release doesn't really make sense.
>>> ---
>>>   src/gallium/auxiliary/util/u_inlines.h   | 16 ++--
>>>   src/gallium/include/pipe/p_context.h | 10 ++
>>>   src/mesa/state_tracker/st_sampler_view.c |  1 -
>>>   3 files changed, 20 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/src/gallium/auxiliary/util/u_inlines.h
>>> b/src/gallium/auxiliary/util/u_inlines.h
>>> index 79f62c32266..790352d7800 100644
>>> --- a/src/gallium/auxiliary/util/u_inlines.h
>>> +++ b/src/gallium/auxiliary/util/u_inlines.h
>>> @@ -142,45 +142,49 @@ pipe_resource_reference(struct pipe_resource
>>> **ptr, struct pipe_resource *tex)
>>>struct pipe_resource *next = old_tex->next;
>>>
>>>old_tex->screen->resource_destroy(old_tex->screen, old_tex);
>>>old_tex = next;
>>> } while (pipe_reference_described(_tex->reference, NULL,
>>>   (debug_reference_descriptor)de
>>> bug_describe_resource));
>>>  }
>>>  *ptr = tex;
>>>   }
>>>
>>> +/**
>>> + * Set *ptr to \p view with proper reference counting.
>>> + *
>>> + * The caller must guarantee that \p view and *ptr must have been
>>> created in
>>> + * the same context (if they exist), and that this must be the current
>>> context.
>>> + */
>>>   static inline void
>>>   pipe_sampler_view_reference(struct pipe_sampler_view **ptr, struct
>>> pipe_sampler_view *view)
>>>   {
>>>  struct pipe_sampler_view *old_view = *ptr;
>>>
>>>  if (pipe_reference_described(&(*ptr)->reference, >reference,
>>>   (debug_reference_descriptor)de
>>> bug_describe_sampler_view))
>>> old_view->context->sampler_view_destroy(old_view->context,
>>> old_view);
>>>  *ptr = view;
>>>   }
>>>
>>>   /**
>>>* Similar to pipe_sampler_view_reference() but always set the pointer
>>> to
>>> - * NULL and pass in an explicit context.  Passing an explicit context
>>> is a
>>> - * work-around for fixing a dangling context pointer problem when
>>> textures
>>> - * are shared by multiple contexts.  XXX fix this someday.
>>> + * NULL and pass in the current context explicitly.
>>> + *
>>> + * If *ptr is non-NULL, it may refer to a view that was created in a
>>> different
>>> + * context (however, that context must still be alive).
>>>*/
>>>   static inline void
>>>   pipe_sampler_view_release(struct pipe_context *ctx,
>>> struct pipe_sampler_view **ptr)
>>>   {
>>>  struct pipe_sampler_view *old_view = *ptr;
>>> -   if (*ptr && (*ptr)->context != ctx) {
>>> -

Re: [Mesa-dev] [PATCH 1/6] gallium: clarify the constraints on sampler_view_destroy

2017-10-10 Thread Nicolai Hähnle 

Same as on IRC:

On 10.10.2017 04:06, Marek Olšák wrote:

Is there any difference with piglit/drawoverhead?


Yes, there is.



If yes, would this be useful?
https://patchwork.freedesktop.org/patch/41241/


Surprisingly, not that much. I'm going to think though a couple of other 
options, but want to already push patch #3; I sent a version that is 
rebased on master and disentangled from the locking stuff.


Cheers,
Nicolai



Marek


On Fri, Oct 6, 2017 at 10:38 PM, Nicolai Hähnle  wrote:

From: Nicolai Hähnle 

r600 expects the context that created the sampler view to still be alive
(there is a per-context list of sampler views).

svga currently bails when the context of destruction is not the same as
creation.

The GL state tracker, which is the only one that runs into the
multi-context subtleties (due to share groups), already guarantees that
sampler views are destroyed before their context of creation is destroyed.

Most drivers are context-agnostic, so the warning message in
pipe_sampler_view_release doesn't really make sense.
---
  src/gallium/auxiliary/util/u_inlines.h   | 16 ++--
  src/gallium/include/pipe/p_context.h | 10 ++
  src/mesa/state_tracker/st_sampler_view.c |  1 -
  3 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/src/gallium/auxiliary/util/u_inlines.h 
b/src/gallium/auxiliary/util/u_inlines.h
index 79f62c32266..790352d7800 100644
--- a/src/gallium/auxiliary/util/u_inlines.h
+++ b/src/gallium/auxiliary/util/u_inlines.h
@@ -142,45 +142,49 @@ pipe_resource_reference(struct pipe_resource **ptr, 
struct pipe_resource *tex)
   struct pipe_resource *next = old_tex->next;

   old_tex->screen->resource_destroy(old_tex->screen, old_tex);
   old_tex = next;
} while (pipe_reference_described(_tex->reference, NULL,
  
(debug_reference_descriptor)debug_describe_resource));
 }
 *ptr = tex;
  }

+/**
+ * Set *ptr to \p view with proper reference counting.
+ *
+ * The caller must guarantee that \p view and *ptr must have been created in
+ * the same context (if they exist), and that this must be the current context.
+ */
  static inline void
  pipe_sampler_view_reference(struct pipe_sampler_view **ptr, struct 
pipe_sampler_view *view)
  {
 struct pipe_sampler_view *old_view = *ptr;

 if (pipe_reference_described(&(*ptr)->reference, >reference,
  
(debug_reference_descriptor)debug_describe_sampler_view))
old_view->context->sampler_view_destroy(old_view->context, old_view);
 *ptr = view;
  }

  /**
   * Similar to pipe_sampler_view_reference() but always set the pointer to
- * NULL and pass in an explicit context.  Passing an explicit context is a
- * work-around for fixing a dangling context pointer problem when textures
- * are shared by multiple contexts.  XXX fix this someday.
+ * NULL and pass in the current context explicitly.
+ *
+ * If *ptr is non-NULL, it may refer to a view that was created in a different
+ * context (however, that context must still be alive).
   */
  static inline void
  pipe_sampler_view_release(struct pipe_context *ctx,
struct pipe_sampler_view **ptr)
  {
 struct pipe_sampler_view *old_view = *ptr;
-   if (*ptr && (*ptr)->context != ctx) {
-  debug_printf_once(("context mis-match in 
pipe_sampler_view_release()\n"));
-   }
 if (pipe_reference_described(&(*ptr)->reference, NULL,
  (debug_reference_descriptor)debug_describe_sampler_view)) 
{
ctx->sampler_view_destroy(ctx, old_view);
 }
 *ptr = NULL;
  }

  static inline void
  pipe_so_target_reference(struct pipe_stream_output_target **ptr,
   struct pipe_stream_output_target *target)
diff --git a/src/gallium/include/pipe/p_context.h 
b/src/gallium/include/pipe/p_context.h
index 4609d4dbf23..087836d1c0c 100644
--- a/src/gallium/include/pipe/p_context.h
+++ b/src/gallium/include/pipe/p_context.h
@@ -501,20 +501,30 @@ struct pipe_context {
 void (*fence_server_sync)(struct pipe_context *pipe,
   struct pipe_fence_handle *fence);

 /**
  * Create a view on a texture to be used by a shader stage.
  */
 struct pipe_sampler_view * (*create_sampler_view)(struct pipe_context *ctx,
   struct pipe_resource 
*texture,
   const struct 
pipe_sampler_view *templat);

+   /**
+* Destroy a view on a texture.
+*
+* \param ctx the current context
+* \param view the view to be destroyed
+*
+* \note The current context may not be the context in which the view was
+*   created (view->context). However, the caller must guarantee that
+*   the context which created the view is still alive.
+*/
 void (*sampler_view_destroy)(struct

Re: [Mesa-dev] [PATCH 1/6] gallium: clarify the constraints on sampler_view_destroy

2017-10-09 Thread Marek Olšák 
Hi Nicolai,

Is there any difference with piglit/drawoverhead?

If yes, would this be useful?
https://patchwork.freedesktop.org/patch/41241/

Marek


On Fri, Oct 6, 2017 at 10:38 PM, Nicolai Hähnle  wrote:
> From: Nicolai Hähnle 
>
> r600 expects the context that created the sampler view to still be alive
> (there is a per-context list of sampler views).
>
> svga currently bails when the context of destruction is not the same as
> creation.
>
> The GL state tracker, which is the only one that runs into the
> multi-context subtleties (due to share groups), already guarantees that
> sampler views are destroyed before their context of creation is destroyed.
>
> Most drivers are context-agnostic, so the warning message in
> pipe_sampler_view_release doesn't really make sense.
> ---
>  src/gallium/auxiliary/util/u_inlines.h   | 16 ++--
>  src/gallium/include/pipe/p_context.h | 10 ++
>  src/mesa/state_tracker/st_sampler_view.c |  1 -
>  3 files changed, 20 insertions(+), 7 deletions(-)
>
> diff --git a/src/gallium/auxiliary/util/u_inlines.h 
> b/src/gallium/auxiliary/util/u_inlines.h
> index 79f62c32266..790352d7800 100644
> --- a/src/gallium/auxiliary/util/u_inlines.h
> +++ b/src/gallium/auxiliary/util/u_inlines.h
> @@ -142,45 +142,49 @@ pipe_resource_reference(struct pipe_resource **ptr, 
> struct pipe_resource *tex)
>   struct pipe_resource *next = old_tex->next;
>
>   old_tex->screen->resource_destroy(old_tex->screen, old_tex);
>   old_tex = next;
>} while (pipe_reference_described(_tex->reference, NULL,
>  
> (debug_reference_descriptor)debug_describe_resource));
> }
> *ptr = tex;
>  }
>
> +/**
> + * Set *ptr to \p view with proper reference counting.
> + *
> + * The caller must guarantee that \p view and *ptr must have been created in
> + * the same context (if they exist), and that this must be the current 
> context.
> + */
>  static inline void
>  pipe_sampler_view_reference(struct pipe_sampler_view **ptr, struct 
> pipe_sampler_view *view)
>  {
> struct pipe_sampler_view *old_view = *ptr;
>
> if (pipe_reference_described(&(*ptr)->reference, >reference,
>  
> (debug_reference_descriptor)debug_describe_sampler_view))
>old_view->context->sampler_view_destroy(old_view->context, old_view);
> *ptr = view;
>  }
>
>  /**
>   * Similar to pipe_sampler_view_reference() but always set the pointer to
> - * NULL and pass in an explicit context.  Passing an explicit context is a
> - * work-around for fixing a dangling context pointer problem when textures
> - * are shared by multiple contexts.  XXX fix this someday.
> + * NULL and pass in the current context explicitly.
> + *
> + * If *ptr is non-NULL, it may refer to a view that was created in a 
> different
> + * context (however, that context must still be alive).
>   */
>  static inline void
>  pipe_sampler_view_release(struct pipe_context *ctx,
>struct pipe_sampler_view **ptr)
>  {
> struct pipe_sampler_view *old_view = *ptr;
> -   if (*ptr && (*ptr)->context != ctx) {
> -  debug_printf_once(("context mis-match in 
> pipe_sampler_view_release()\n"));
> -   }
> if (pipe_reference_described(&(*ptr)->reference, NULL,
>  
> (debug_reference_descriptor)debug_describe_sampler_view)) {
>ctx->sampler_view_destroy(ctx, old_view);
> }
> *ptr = NULL;
>  }
>
>  static inline void
>  pipe_so_target_reference(struct pipe_stream_output_target **ptr,
>   struct pipe_stream_output_target *target)
> diff --git a/src/gallium/include/pipe/p_context.h 
> b/src/gallium/include/pipe/p_context.h
> index 4609d4dbf23..087836d1c0c 100644
> --- a/src/gallium/include/pipe/p_context.h
> +++ b/src/gallium/include/pipe/p_context.h
> @@ -501,20 +501,30 @@ struct pipe_context {
> void (*fence_server_sync)(struct pipe_context *pipe,
>   struct pipe_fence_handle *fence);
>
> /**
>  * Create a view on a texture to be used by a shader stage.
>  */
> struct pipe_sampler_view * (*create_sampler_view)(struct pipe_context 
> *ctx,
>   struct pipe_resource 
> *texture,
>   const struct 
> pipe_sampler_view *templat);
>
> +   /**
> +* Destroy a view on a texture.
> +*
> +* \param ctx the current context
> +* \param view the view to be destroyed
> +*
> +* \note The current context may not be the context in which the view was
> +*   created (view->context). However, the caller must guarantee that
> +*   the context which created the view is still alive.
> +*/
> void (*sampler_view_destroy)(struct pipe_context *ctx,
>  struct pipe_sampler_view *view);
>
>
> /**
>  * Get a

Re: [Mesa-dev] [PATCH 1/6] gallium: clarify the constraints on sampler_view_destroy

2017-10-06 Thread Nicolai Hähnle 
FWIW, the drivers that really are affected currently are SVGA and 
possibly virgl, because they pass Gallium calls on to a supervisor. 
Since we guarantee that the creation context is still alive, those 
drivers could fix any issues by adding samplers that are destroyed from 
a different context to an "orphan" list which is regularly cleaned up by 
the creating context.


Cheers,
Nicolai

On 06.10.2017 22:38, Nicolai Hähnle wrote:

From: Nicolai Hähnle 

r600 expects the context that created the sampler view to still be alive
(there is a per-context list of sampler views).

svga currently bails when the context of destruction is not the same as
creation.

The GL state tracker, which is the only one that runs into the
multi-context subtleties (due to share groups), already guarantees that
sampler views are destroyed before their context of creation is destroyed.

Most drivers are context-agnostic, so the warning message in
pipe_sampler_view_release doesn't really make sense.
---
  src/gallium/auxiliary/util/u_inlines.h   | 16 ++--
  src/gallium/include/pipe/p_context.h | 10 ++
  src/mesa/state_tracker/st_sampler_view.c |  1 -
  3 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/src/gallium/auxiliary/util/u_inlines.h 
b/src/gallium/auxiliary/util/u_inlines.h
index 79f62c32266..790352d7800 100644
--- a/src/gallium/auxiliary/util/u_inlines.h
+++ b/src/gallium/auxiliary/util/u_inlines.h
@@ -142,45 +142,49 @@ pipe_resource_reference(struct pipe_resource **ptr, 
struct pipe_resource *tex)
   struct pipe_resource *next = old_tex->next;
  
   old_tex->screen->resource_destroy(old_tex->screen, old_tex);

   old_tex = next;
} while (pipe_reference_described(_tex->reference, NULL,
  
(debug_reference_descriptor)debug_describe_resource));
 }
 *ptr = tex;
  }
  
+/**

+ * Set *ptr to \p view with proper reference counting.
+ *
+ * The caller must guarantee that \p view and *ptr must have been created in
+ * the same context (if they exist), and that this must be the current context.
+ */
  static inline void
  pipe_sampler_view_reference(struct pipe_sampler_view **ptr, struct 
pipe_sampler_view *view)
  {
 struct pipe_sampler_view *old_view = *ptr;
  
 if (pipe_reference_described(&(*ptr)->reference, >reference,

  
(debug_reference_descriptor)debug_describe_sampler_view))
old_view->context->sampler_view_destroy(old_view->context, old_view);
 *ptr = view;
  }
  
  /**

   * Similar to pipe_sampler_view_reference() but always set the pointer to
- * NULL and pass in an explicit context.  Passing an explicit context is a
- * work-around for fixing a dangling context pointer problem when textures
- * are shared by multiple contexts.  XXX fix this someday.
+ * NULL and pass in the current context explicitly.
+ *
+ * If *ptr is non-NULL, it may refer to a view that was created in a different
+ * context (however, that context must still be alive).
   */
  static inline void
  pipe_sampler_view_release(struct pipe_context *ctx,
struct pipe_sampler_view **ptr)
  {
 struct pipe_sampler_view *old_view = *ptr;
-   if (*ptr && (*ptr)->context != ctx) {
-  debug_printf_once(("context mis-match in 
pipe_sampler_view_release()\n"));
-   }
 if (pipe_reference_described(&(*ptr)->reference, NULL,
  (debug_reference_descriptor)debug_describe_sampler_view)) 
{
ctx->sampler_view_destroy(ctx, old_view);
 }
 *ptr = NULL;
  }
  
  static inline void

  pipe_so_target_reference(struct pipe_stream_output_target **ptr,
   struct pipe_stream_output_target *target)
diff --git a/src/gallium/include/pipe/p_context.h 
b/src/gallium/include/pipe/p_context.h
index 4609d4dbf23..087836d1c0c 100644
--- a/src/gallium/include/pipe/p_context.h
+++ b/src/gallium/include/pipe/p_context.h
@@ -501,20 +501,30 @@ struct pipe_context {
 void (*fence_server_sync)(struct pipe_context *pipe,
   struct pipe_fence_handle *fence);
  
 /**

  * Create a view on a texture to be used by a shader stage.
  */
 struct pipe_sampler_view * (*create_sampler_view)(struct pipe_context *ctx,
   struct pipe_resource 
*texture,
   const struct 
pipe_sampler_view *templat);
  
+   /**

+* Destroy a view on a texture.
+*
+* \param ctx the current context
+* \param view the view to be destroyed
+*
+* \note The current context may not be the context in which the view was
+*   created (view->context). However, the caller must guarantee that
+*   the context which created the view is still alive.
+*/
 void (*sampler_view_destroy)(struct pipe_context *ctx,
  struct

[Mesa-dev] [PATCH 1/6] gallium: clarify the constraints on sampler_view_destroy

2017-10-06 Thread Nicolai Hähnle 
From: Nicolai Hähnle 

r600 expects the context that created the sampler view to still be alive
(there is a per-context list of sampler views).

svga currently bails when the context of destruction is not the same as
creation.

The GL state tracker, which is the only one that runs into the
multi-context subtleties (due to share groups), already guarantees that
sampler views are destroyed before their context of creation is destroyed.

Most drivers are context-agnostic, so the warning message in
pipe_sampler_view_release doesn't really make sense.
---
 src/gallium/auxiliary/util/u_inlines.h   | 16 ++--
 src/gallium/include/pipe/p_context.h | 10 ++
 src/mesa/state_tracker/st_sampler_view.c |  1 -
 3 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/src/gallium/auxiliary/util/u_inlines.h 
b/src/gallium/auxiliary/util/u_inlines.h
index 79f62c32266..790352d7800 100644
--- a/src/gallium/auxiliary/util/u_inlines.h
+++ b/src/gallium/auxiliary/util/u_inlines.h
@@ -142,45 +142,49 @@ pipe_resource_reference(struct pipe_resource **ptr, 
struct pipe_resource *tex)
  struct pipe_resource *next = old_tex->next;
 
  old_tex->screen->resource_destroy(old_tex->screen, old_tex);
  old_tex = next;
   } while (pipe_reference_described(_tex->reference, NULL,
 
(debug_reference_descriptor)debug_describe_resource));
}
*ptr = tex;
 }
 
+/**
+ * Set *ptr to \p view with proper reference counting.
+ *
+ * The caller must guarantee that \p view and *ptr must have been created in
+ * the same context (if they exist), and that this must be the current context.
+ */
 static inline void
 pipe_sampler_view_reference(struct pipe_sampler_view **ptr, struct 
pipe_sampler_view *view)
 {
struct pipe_sampler_view *old_view = *ptr;
 
if (pipe_reference_described(&(*ptr)->reference, >reference,
 
(debug_reference_descriptor)debug_describe_sampler_view))
   old_view->context->sampler_view_destroy(old_view->context, old_view);
*ptr = view;
 }
 
 /**
  * Similar to pipe_sampler_view_reference() but always set the pointer to
- * NULL and pass in an explicit context.  Passing an explicit context is a
- * work-around for fixing a dangling context pointer problem when textures
- * are shared by multiple contexts.  XXX fix this someday.
+ * NULL and pass in the current context explicitly.
+ *
+ * If *ptr is non-NULL, it may refer to a view that was created in a different
+ * context (however, that context must still be alive).
  */
 static inline void
 pipe_sampler_view_release(struct pipe_context *ctx,
   struct pipe_sampler_view **ptr)
 {
struct pipe_sampler_view *old_view = *ptr;
-   if (*ptr && (*ptr)->context != ctx) {
-  debug_printf_once(("context mis-match in 
pipe_sampler_view_release()\n"));
-   }
if (pipe_reference_described(&(*ptr)->reference, NULL,
 (debug_reference_descriptor)debug_describe_sampler_view)) {
   ctx->sampler_view_destroy(ctx, old_view);
}
*ptr = NULL;
 }
 
 static inline void
 pipe_so_target_reference(struct pipe_stream_output_target **ptr,
  struct pipe_stream_output_target *target)
diff --git a/src/gallium/include/pipe/p_context.h 
b/src/gallium/include/pipe/p_context.h
index 4609d4dbf23..087836d1c0c 100644
--- a/src/gallium/include/pipe/p_context.h
+++ b/src/gallium/include/pipe/p_context.h
@@ -501,20 +501,30 @@ struct pipe_context {
void (*fence_server_sync)(struct pipe_context *pipe,
  struct pipe_fence_handle *fence);
 
/**
 * Create a view on a texture to be used by a shader stage.
 */
struct pipe_sampler_view * (*create_sampler_view)(struct pipe_context *ctx,
  struct pipe_resource 
*texture,
  const struct 
pipe_sampler_view *templat);
 
+   /**
+* Destroy a view on a texture.
+*
+* \param ctx the current context
+* \param view the view to be destroyed
+*
+* \note The current context may not be the context in which the view was
+*   created (view->context). However, the caller must guarantee that
+*   the context which created the view is still alive.
+*/
void (*sampler_view_destroy)(struct pipe_context *ctx,
 struct pipe_sampler_view *view);
 
 
/**
 * Get a surface which is a "view" into a resource, used by
 * render target / depth stencil stages.
 */
struct pipe_surface *(*create_surface)(struct pipe_context *ctx,
   struct pipe_resource *resource,
diff --git a/src/mesa/state_tracker/st_sampler_view.c 
b/src/mesa/state_tracker/st_sampler_view.c
index fbf0aaeb03a..d1715a888d9 100644
--- a/src/mesa/state_tracker/st_sampler_view.c
+++