[Mesa-dev] [PATCH v3 1/1] clover: use pipe_resource references

[Francisco Jerez]

Jan Vesely <jan.vesely at rutgers.edu> writes:

> On Thu, 2017-03-16 at 17:22 -0700, Francisco Jerez wrote:
>> Jan Vesely <jan.vesely at rutgers.edu> writes:
>> 
>> > On Thu, 2017-03-16 at 15:24 -0700, Francisco Jerez wrote:
>> > > Jan Vesely <jan.vesely at rutgers.edu> writes:
>> > > 
>> > > > v2: buffers are created with one reference.
>> > > > v3: add pipe_resource reference to mapping object
>> > > > 
>> > > 
>> > > Mapping objects are supposed to be short-lived, they're logically part
>> > > of the parent resource object so they shouldn't ever out-live it.  What
>> > > is this useful for?
>> > 
>> > currently they can outlive the underlying pipe_resource. pipe_resource
>> > is destroyed in root_resource destructor, while the list of mappings is
>> > destroyed after resource destructor.
>> 
>> Right.  I guess the problem is that the pipe_transfer object associated
>> to the clover::mapping object holds a pointer to the backing
>> pipe_resource object but it fails to increment its reference count?  I
>> guess that's the reason why v2 didn't help?
>
> yes, though the pointer is hidden somewhere. I thought pxfer->resource
> might be it, but it's not, and digging deeper into the structure didn't
> sound like a good idea to me.
>

What is pxfer->resource about in that case?

>> 
>> > this is arguably an application bug. the piglit test does not call
>> > clUnmapMemObject(), but it'd be nice to not access freed memory.
>> > 
>> > Vedran's alternative to clear the list before destroying pipe_resource
>> > works as well (assert that the list is empty in resource destructor
>> > would help spot the issue).
>> > 
>> 
>> Assuming that pipe_transfers are supposed *not* to hold a reference to
>> the underlying pipe_resource, which implies that the caller must
>> guarantee it will never outlive its backing resource, it sounds like the
>> minimal solution would be to have clover::mapping make the same
>> assumptions.  You could probably achieve that in one line of code by
>> clearing the mapping list from the clover::resource destructor as you
>> suggest above.
>
> I'd say the interface would be nicer if pipe_transfers did hold a
> reference (or at least a mapping count to assert on), but I have no
> plans to go that route.
> the problem is a bit more complicated by the fact that pipe_resource is
> handled by root_resource, while the list of mappings is private to
> parent class resource.
>
> Vedran's patch is here:
> https://lists.freedesktop.org/archives/mesa-dev/2017-March/147092.html
>
> I thought that using references would be nicer, as it looked useful for
> device shared buffers, but that no longer applies.
>
> Jan
>
>> 
>> > Jan
>> > 
>> > > 
>> > > > CC: "17.0 13.0" <mesa-stable at lists.freedesktop.org>
>> > > > 
>> > > > Signed-off-by: Jan Vesely <jan.vesely at rutgers.edu>
>> > > > ---
>> > > >  src/gallium/state_trackers/clover/core/resource.cpp | 11 ++++++++---
>> > > >  src/gallium/state_trackers/clover/core/resource.hpp |  7 ++++---
>> > > >  2 files changed, 12 insertions(+), 6 deletions(-)
>> > > > 
>> > > > diff --git a/src/gallium/state_trackers/clover/core/resource.cpp b/src/gallium/state_trackers/clover/core/resource.cpp
>> > > > index 06fd3f6..83e3c26 100644
>> > > > --- a/src/gallium/state_trackers/clover/core/resource.cpp
>> > > > +++ b/src/gallium/state_trackers/clover/core/resource.cpp
>> > > > @@ -25,6 +25,7 @@
>> > > >  #include "pipe/p_screen.h"
>> > > >  #include "util/u_sampler.h"
>> > > >  #include "util/u_format.h"
>> > > > +#include "util/u_inlines.h"
>> > > >  
>> > > >  using namespace clover;
>> > > >  
>> > > > @@ -176,7 +177,7 @@ root_resource::root_resource(clover::device &dev, memory_obj &obj,
>> > > >  }
>> > > >  
>> > > >  root_resource::~root_resource() {
>> > > > -   device().pipe->resource_destroy(device().pipe, pipe);
>> > > > +   pipe_resource_reference(&this->pipe, NULL);
>> > > >  }
>> > > >  
>> > > >  sub_resource::sub_resource(resource &r, const vector &offset) :
>> > > > @@ -202,18 +203,21 @@ mapping::mapping(command_queue &q, resource &r,
>> > > >        pxfer = NULL;
>> > > >        throw error(CL_OUT_OF_RESOURCES);
>> > > >     }
>> > > > +   pipe_resource_reference(&res, r.pipe);
>> > > >  }
>> > > >  
>> > > >  mapping::mapping(mapping &&m) :
>> > > > -   pctx(m.pctx), pxfer(m.pxfer), p(m.p) {
>> > > > +   pctx(m.pctx), pxfer(m.pxfer), res(m.res), p(m.p) {
>> > > >     m.pctx = NULL;
>> > > >     m.pxfer = NULL;
>> > > > +   m.res = NULL;
>> > > >     m.p = NULL;
>> > > >  }
>> > > >  
>> > > >  mapping::~mapping() {
>> > > >     if (pxfer) {
>> > > >        pctx->transfer_unmap(pctx, pxfer);
>> > > >     }
>> > > > +   pipe_resource_reference(&res, NULL);
>> > > >  }
>> > > >  
>> > > > @@ -222,5 +226,6 @@ mapping::operator=(mapping m) {
>> > > >     std::swap(pctx, m.pctx);
>> > > >     std::swap(pxfer, m.pxfer);
>> > > > +   std::swap(res, m.res);
>> > > >     std::swap(p, m.p);
>> > > >     return *this;
>> > > >  }
>> > > > diff --git a/src/gallium/state_trackers/clover/core/resource.hpp b/src/gallium/state_trackers/clover/core/resource.hpp
>> > > > index 9993dcb..cea9617 100644
>> > > > --- a/src/gallium/state_trackers/clover/core/resource.hpp
>> > > > +++ b/src/gallium/state_trackers/clover/core/resource.hpp
>> > > > @@ -123,9 +123,10 @@ namespace clover {
>> > > >        }
>> > > >  
>> > > >     private:
>> > > > -      pipe_context *pctx;
>> > > > -      pipe_transfer *pxfer;
>> > > > -      void *p;
>> > > > +      pipe_context *pctx = NULL;
>> > > > +      pipe_transfer *pxfer = NULL;
>> > > > +      pipe_resource *res = NULL;
>> > > > +      void *p = NULL;
>> > > >     };
>> > > >  }
>> > > >  
>> > > > -- 
>> > > > 2.9.3
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