drm/amd/display: Use atomic types for ref_count

Current ref_count inc/dec is not guarded by locks which leads to
a raced condition where two threads try to access the variable
at the same time. In this case, both might act on the same cached
value and inc/dec from the same value, rather than inc/dec by 2.
Signed-off-by: Jerry Zuo <Jerry.Zuo@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc.c

@@ -454,7 +454,7 @@ static bool construct(struct core_dc *dc,
 		goto val_ctx_fail;
 	}
 
-	dc->current_context->ref_count++;
+	atomic_inc(&dc->current_context->ref_count);
 
 	dc_ctx->cgs_device = init_params->cgs_device;
 	dc_ctx->driver_context = init_params->driver;
@@ -704,7 +704,7 @@ struct validate_context *dc_get_validate_context(
 	if (context == NULL)
 		goto context_alloc_fail;
 
-	++context->ref_count;
+	atomic_inc(&context->ref_count);
 
 	if (!is_validation_required(core_dc, set, set_count)) {
 		dc_resource_validate_ctx_copy_construct(core_dc->current_context, context);
@@ -748,7 +748,7 @@ bool dc_validate_resources(
 	if (context == NULL)
 		goto context_alloc_fail;
 
-	++context->ref_count;
+	atomic_inc(&context->ref_count);
 
 	result = core_dc->res_pool->funcs->validate_with_context(
 				core_dc, set, set_count, context, NULL);
@@ -782,7 +782,7 @@ bool dc_validate_guaranteed(
 	if (context == NULL)
 		goto context_alloc_fail;
 
-	++context->ref_count;
+	atomic_inc(&context->ref_count);
 
 	result = core_dc->res_pool->funcs->validate_guaranteed(
 					core_dc, stream, context);
@@ -1090,7 +1090,7 @@ bool dc_commit_streams(
 	if (context == NULL)
 		goto context_alloc_fail;
 
-	++context->ref_count;
+	atomic_inc(&context->ref_count);
 
 	result = core_dc->res_pool->funcs->validate_with_context(
 			core_dc, set, stream_count, context, core_dc->current_context);
@@ -1203,16 +1203,16 @@ bool dc_commit_planes_to_stream(
 
 void dc_retain_validate_context(struct validate_context *context)
 {
-	ASSERT(context->ref_count > 0);
-	++context->ref_count;
+	ASSERT(atomic_read(&context->ref_count) > 0);
+	atomic_inc(&context->ref_count);
 }
 
 void dc_release_validate_context(struct validate_context *context)
 {
-	ASSERT(context->ref_count > 0);
-	--context->ref_count;
+	ASSERT(atomic_read(&context->ref_count) > 0);
+	atomic_dec(&context->ref_count);
 
-	if (context->ref_count == 0) {
+	if (atomic_read(&context->ref_count) == 0) {
 		dc_resource_validate_ctx_destruct(context);
 		dm_free(context);
 	}
@@ -1485,7 +1485,7 @@ void dc_update_planes_and_stream(struct dc *dc,
 		if (context == NULL)
 				goto context_alloc_fail;
 
-		++context->ref_count;
+		atomic_inc(&context->ref_count);
 
 		dc_resource_validate_ctx_copy_construct(
 				core_dc->current_context, context);
@@ -1800,7 +1800,7 @@ void dc_set_power_state(
 	enum dc_acpi_cm_power_state power_state)
 {
 	struct core_dc *core_dc = DC_TO_CORE(dc);
-	int ref_count;
+	atomic_t ref_count;
 
 	switch (power_state) {
 	case DC_ACPI_CM_POWER_STATE_D0:

drivers/gpu/drm/amd/display/dc/core/dc_resource.c

@@ -2238,7 +2238,7 @@ void dc_resource_validate_ctx_copy_construct(
 		struct validate_context *dst_ctx)
 {
 	int i, j;
-	int ref_count = dst_ctx->ref_count;
+	atomic_t ref_count = dst_ctx->ref_count;
 
 	*dst_ctx = *src_ctx;
 

drivers/gpu/drm/amd/display/dc/core/dc_sink.c

@@ -63,16 +63,16 @@ static bool construct(struct dc_sink *sink, const struct dc_sink_init_data *init
 
 void dc_sink_retain(struct dc_sink *sink)
 {
-	ASSERT(sink->ref_count > 0);
-	++sink->ref_count;
+	ASSERT(atomic_read(&sink->ref_count) > 0);
+	atomic_inc(&sink->ref_count);
 }
 
 void dc_sink_release(struct dc_sink *sink)
 {
-	ASSERT(sink->ref_count > 0);
-	--sink->ref_count;
+	ASSERT(atomic_read(&sink->ref_count) > 0);
+	atomic_dec(&sink->ref_count);
 
-	if (sink->ref_count == 0) {
+	if (atomic_read(&sink->ref_count) == 0) {
 		destruct(sink);
 		dm_free(sink);
 	}
@@ -88,7 +88,7 @@ struct dc_sink *dc_sink_create(const struct dc_sink_init_data *init_params)
 	if (false == construct(sink, init_params))
 		goto construct_fail;
 
-	++sink->ref_count;
+	atomic_inc(&sink->ref_count);
 
 	return sink;
 

drivers/gpu/drm/amd/display/dc/core/dc_stream.c

@@ -96,19 +96,17 @@ static void destruct(struct dc_stream_state *stream)
 
 void dc_stream_retain(struct dc_stream_state *stream)
 {
-
-	ASSERT(stream->ref_count > 0);
-	stream->ref_count++;
+	ASSERT(atomic_read(&stream->ref_count) > 0);
+	atomic_inc(&stream->ref_count);
 }
 
 void dc_stream_release(struct dc_stream_state *stream)
 {
-
 	if (stream != NULL) {
-		ASSERT(stream->ref_count > 0);
-		stream->ref_count--;
+		ASSERT(atomic_read(&stream->ref_count) > 0);
+		atomic_dec(&stream->ref_count);
 
-		if (stream->ref_count == 0) {
+		if (atomic_read(&stream->ref_count) == 0) {
 			destruct(stream);
 			dm_free(stream);
 		}
@@ -131,7 +129,7 @@ struct dc_stream_state *dc_create_stream_for_sink(
 	if (false == construct(stream, sink))
 			goto construct_fail;
 
-	stream->ref_count++;
+	atomic_inc(&stream->ref_count);
 
 	return stream;
 

drivers/gpu/drm/amd/display/dc/core/dc_surface.c

@@ -76,7 +76,7 @@ struct dc_plane_state *dc_create_plane_state(const struct dc *dc)
 	if (false == construct(core_dc->ctx, plane_state))
 		goto construct_fail;
 
-	++plane_state->ref_count;
+	atomic_inc(&plane_state->ref_count);
 
 	return plane_state;
 
@@ -122,16 +122,16 @@ const struct dc_plane_status *dc_plane_get_status(
 
 void dc_plane_state_retain(struct dc_plane_state *plane_state)
 {
-	ASSERT(plane_state->ref_count > 0);
-	++plane_state->ref_count;
+	ASSERT(atomic_read(&plane_state->ref_count) > 0);
+	atomic_inc(&plane_state->ref_count);
 }
 
 void dc_plane_state_release(struct dc_plane_state *plane_state)
 {
-	ASSERT(plane_state->ref_count > 0);
-	--plane_state->ref_count;
+	ASSERT(atomic_read(&plane_state->ref_count) > 0);
+	atomic_dec(&plane_state->ref_count);
 
-	if (plane_state->ref_count == 0) {
+	if (atomic_read(&plane_state->ref_count) == 0) {
 		destruct(plane_state);
 		dm_free(plane_state);
 	}
@@ -139,16 +139,16 @@ void dc_plane_state_release(struct dc_plane_state *plane_state)
 
 void dc_gamma_retain(struct dc_gamma *gamma)
 {
-	ASSERT(gamma->ref_count > 0);
-	++gamma->ref_count;
+	ASSERT(atomic_read(&gamma->ref_count) > 0);
+	atomic_inc(&gamma->ref_count);
 }
 
 void dc_gamma_release(struct dc_gamma **gamma)
 {
-	ASSERT((*gamma)->ref_count > 0);
-	--(*gamma)->ref_count;
+	ASSERT(atomic_read(&(*gamma)->ref_count) > 0);
+	atomic_dec(&(*gamma)->ref_count);
 
-	if ((*gamma)->ref_count == 0)
+	if (atomic_read(&(*gamma)->ref_count) == 0)
 		dm_free((*gamma));
 
 	*gamma = NULL;
@@ -161,7 +161,7 @@ struct dc_gamma *dc_create_gamma()
 	if (gamma == NULL)
 		goto alloc_fail;
 
-	++gamma->ref_count;
+	atomic_inc(&gamma->ref_count);
 
 	return gamma;
 
@@ -171,16 +171,16 @@ struct dc_gamma *dc_create_gamma()
 
 void dc_transfer_func_retain(struct dc_transfer_func *tf)
 {
-	ASSERT(tf->ref_count > 0);
-	++tf->ref_count;
+	ASSERT(atomic_read(&tf->ref_count) > 0);
+	atomic_inc(&tf->ref_count);
 }
 
 void dc_transfer_func_release(struct dc_transfer_func *tf)
 {
-	ASSERT(tf->ref_count > 0);
-	--tf->ref_count;
+	ASSERT(atomic_read(&tf->ref_count) > 0);
+	atomic_dec(&tf->ref_count);
 
-	if (tf->ref_count == 0)
+	if (atomic_read(&tf->ref_count) == 0)
 		dm_free(tf);
 }
 
@@ -191,7 +191,7 @@ struct dc_transfer_func *dc_create_transfer_func()
 	if (tf == NULL)
 		goto alloc_fail;
 
-	++tf->ref_count;
+	atomic_inc(&tf->ref_count);
 
 	return tf;
 

drivers/gpu/drm/amd/display/dc/dc.h

@@ -295,7 +295,7 @@ struct dc_transfer_func {
 	enum dc_transfer_func_type type;
 	enum dc_transfer_func_predefined tf;
 	struct dc_context *ctx;
-	int ref_count;
+	atomic_t ref_count;
 };
 
 /*
@@ -342,7 +342,7 @@ struct dc_plane_state {
 
 	/* private to dc_surface.c */
 	enum dc_irq_source irq_source;
-	int ref_count;
+	atomic_t ref_count;
 };
 
 struct dc_plane_info {
@@ -518,7 +518,7 @@ struct dc_stream_state {
 	struct dc_stream_status status;
 
 	/* from stream struct */
-	int ref_count;
+	atomic_t ref_count;
 };
 
 struct dc_stream_update {
@@ -902,7 +902,7 @@ struct dc_sink {
 	struct dc_context *ctx;
 
 	/* private to dc_sink.c */
-	int ref_count;
+	atomic_t ref_count;
 };
 
 void dc_sink_retain(struct dc_sink *sink);

drivers/gpu/drm/amd/display/dc/dc_hw_types.h

@@ -433,7 +433,7 @@ struct dc_gamma {
 	struct dc_context *ctx;
 
 	/* private to dc_surface.c */
-	int ref_count;
+	atomic_t ref_count;
 };
 
 /* Used by both ipp amd opp functions*/

drivers/gpu/drm/amd/display/dc/inc/core_types.h

@@ -260,7 +260,7 @@ struct validate_context {
 	struct dcn_bw_internal_vars dcn_bw_vars;
 #endif
 
-	int ref_count;
+	atomic_t ref_count;
 };
 
 #endif /* _CORE_TYPES_H_ */