Re: [PATCH v2] drm/i915: Assert that the context pin_counts do not overflow

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> This should be impossible, but let's assert that we do not pin a context
> 4 billion times before retiring!
>
> v2: Fix the assertion -- the patch had just one job to do!
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Mika Kuoppala <mika.kuoppala@intel.com>

Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>

> ---
>  drivers/gpu/drm/i915/intel_lrc.c        | 1 +
>  drivers/gpu/drm/i915/intel_ringbuffer.c | 1 +
>  2 files changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index 73386b7b22fa..aad107337530 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -748,6 +748,7 @@ static int execlists_context_pin(struct intel_engine_cs *engine,
>  
>  	if (ce->pin_count++)
>  		return 0;
> +	GEM_BUG_ON(!ce->pin_count); /* no overflow please! */
>  
>  	if (!ce->state) {
>  		ret = execlists_context_deferred_alloc(ctx, engine);
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index e895c99f5dd9..be908e2a52ea 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -1445,6 +1445,7 @@ static int intel_ring_context_pin(struct intel_engine_cs *engine,
>  
>  	if (ce->pin_count++)
>  		return 0;
> +	GEM_BUG_ON(!ce->pin_count); /* no overflow please! */
>  
>  	if (ce->state) {
>  		ret = context_pin(ctx);
> -- 
> 2.11.0
>
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