On Fri, 2015-08-07 at 10:09 -0700, Ian Romanick wrote:
> I know we've talked about this about 100 times, but something in the
> back of my mind tells me that we have a pre-existing race. What happens
> if the p_atomic_dec_zero happens on thread A while thread B is between
> the _mesa_lookup_renderbuffer call and the _mesa_reference_renderbuffer
> call on the same object? Won't thread A free the memory out from under
> thread B?
Right I think I follow. It looks like the bind would silently fail right?
>
> On 08/06/2015 05:10 PM, Matt Turner wrote:
> > ---
> > src/mesa/main/mtypes.h | 1 -
> > src/mesa/main/samplerobj.c | 16 +++-------------
> > 2 files changed, 3 insertions(+), 14 deletions(-)
> >
> > diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
> > index 2adfae2..fcc527f 100644
> > --- a/src/mesa/main/mtypes.h
> > +++ b/src/mesa/main/mtypes.h
> > @@ -1153,7 +1153,6 @@ typedef enum
> > */
> > struct gl_sampler_object
> > {
> > - mtx_t Mutex;
> > GLuint Name;
> > GLint RefCount;
> > GLchar *Label; /**< GL_KHR_debug */
> > diff --git a/src/mesa/main/samplerobj.c b/src/mesa/main/samplerobj.c
> > index c7b9666..dba2087 100644
> > --- a/src/mesa/main/samplerobj.c
> > +++ b/src/mesa/main/samplerobj.c
> > @@ -38,6 +38,7 @@
> > #include "main/macros.h"
> > #include "main/mtypes.h"
> > #include "main/samplerobj.h"
> > +#include "util/u_atomic.h"
> >
> >
> > struct gl_sampler_object *
> > @@ -85,16 +86,9 @@ _mesa_reference_sampler_object_(struct gl_context *ctx,
> >
> > if (*ptr) {
> > /* Unreference the old sampler */
> > - GLboolean deleteFlag = GL_FALSE;
> > struct gl_sampler_object *oldSamp = *ptr;
> >
> > - mtx_lock(&oldSamp->Mutex);
> > - assert(oldSamp->RefCount > 0);
> > - oldSamp->RefCount--;
> > - deleteFlag = (oldSamp->RefCount == 0);
> > - mtx_unlock(&oldSamp->Mutex);
> > -
> > - if (deleteFlag) {
> > + if (p_atomic_dec_zero(&oldSamp->RefCount)) {
> > assert(ctx->Driver.DeleteSamplerObject);
> > ctx->Driver.DeleteSamplerObject(ctx, oldSamp);
> > }
> > @@ -105,7 +99,6 @@ _mesa_reference_sampler_object_(struct gl_context *ctx,
> >
> > if (samp) {
> > /* reference new sampler */
> > - mtx_lock(&samp->Mutex);
> > if (samp->RefCount == 0) {
> > /* this sampler's being deleted (look just above) */
> > /* Not sure this can every really happen. Warn if it does. */
> > @@ -113,10 +106,9 @@ _mesa_reference_sampler_object_(struct gl_context
> > *ctx,
> > *ptr = NULL;
> > }
> > else {
> > - samp->RefCount++;
> > + p_atomic_inc(&samp->RefCount);
> > *ptr = samp;
> > }
> > - mtx_unlock(&samp->Mutex);
> > }
> > }
> >
> > @@ -127,7 +119,6 @@ _mesa_reference_sampler_object_(struct gl_context
> > *ctx,
> > static void
> > _mesa_init_sampler_object(struct gl_sampler_object *sampObj, GLuint name)
> > {
> > - mtx_init(&sampObj->Mutex, mtx_plain);
> > sampObj->Name = name;
> > sampObj->RefCount = 1;
> > sampObj->WrapS = GL_REPEAT;
> > @@ -170,7 +161,6 @@ static void
> > _mesa_delete_sampler_object(struct gl_context *ctx,
> > struct gl_sampler_object *sampObj)
> > {
> > - mtx_destroy(&sampObj->Mutex);
> > free(sampObj->Label);
> > free(sampObj);
> > }
> >
>
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