[Mesa-dev] [PATCH] mesa: framebuffer refcounting with atomic ops

[Marek Olšák]

I take back my Rb.

If *ptr == fb, it will crash.

Also, it's safer to first increment the fb counter and then decrement
the *ptr counter.

Basically, copy what pipe_reference_described does.

Marek

On Tue, Aug 15, 2017 at 3:04 PM, Marek Olšák <maraeo at gmail.com> wrote:
> Reviewed-by: Marek Olšák <marek.olsak at amd.com>
>
> Marek
>
> On Tue, Aug 15, 2017 at 2:03 PM, Tapani Pälli <tapani.palli at intel.com> wrote:
>> Signed-off-by: Tapani Pälli <tapani.palli at intel.com>
>> ---
>>  src/mesa/main/framebuffer.c | 19 +++++--------------
>>  1 file changed, 5 insertions(+), 14 deletions(-)
>>
>> Use atomic ops in same manner as for shader objects, IMO makes
>> code easier to read.
>>
>> diff --git a/src/mesa/main/framebuffer.c b/src/mesa/main/framebuffer.c
>> index 039762a074..69e28c8af7 100644
>> --- a/src/mesa/main/framebuffer.c
>> +++ b/src/mesa/main/framebuffer.c
>> @@ -45,7 +45,7 @@
>>  #include "texobj.h"
>>  #include "glformats.h"
>>  #include "state.h"
>> -
>> +#include "util/u_atomic.h"
>>
>>
>>  /**
>> @@ -243,25 +243,16 @@ _mesa_reference_framebuffer_(struct gl_framebuffer **ptr,
>>  {
>>     if (*ptr) {
>>        /* unreference old renderbuffer */
>> -      GLboolean deleteFlag = GL_FALSE;
>>        struct gl_framebuffer *oldFb = *ptr;
>> -
>> -      mtx_lock(&oldFb->Mutex);
>> -      assert(oldFb->RefCount > 0);
>> -      oldFb->RefCount--;
>> -      deleteFlag = (oldFb->RefCount == 0);
>> -      mtx_unlock(&oldFb->Mutex);
>> -
>> -      if (deleteFlag)
>> -         oldFb->Delete(oldFb);
>> +      assert(p_atomic_read(&oldFb->RefCount) > 0);
>> +      if (p_atomic_dec_zero(&oldFb->RefCount))
>> +          oldFb->Delete(oldFb);
>>
>>        *ptr = NULL;
>>     }
>>
>>     if (fb) {
>> -      mtx_lock(&fb->Mutex);
>> -      fb->RefCount++;
>> -      mtx_unlock(&fb->Mutex);
>> +      p_atomic_inc(&fb->RefCount);
>>        *ptr = fb;
>>     }
>>  }
>> --
>> 2.13.5
>>
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