From: Corbin McElhanney <corbin.mcelhanney@amd.com>
Date: Wed, 9 Aug 2017 10:30:28 -0400
Subject: drm/amd/display: Add comment explaining context free
Git-commit: e771aae02baa59386972faec491cd221c169ed53
Patch-mainline: v4.15-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166
This comment explains a previous change that adds some complexity
to the context free in dc:
commit 9ad58779a895 ("drm/amd/display: Fix accessing freed memory")
Signed-off-by: Corbin McElhanney <corbin.mcelhanney@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
drivers/gpu/drm/amd/display/dc/core/dc.c | 9 +++++++++
1 file changed, 9 insertions(+)
--- a/drivers/gpu/drm/amd/display/dc/core/dc.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc.c
@@ -1740,6 +1740,15 @@ void dc_update_planes_and_stream(struct
}
if (core_dc->current_context != context) {
+
+ /* Since memory free requires elevated IRQL, an interrupt
+ * request is generated by mem free. If this happens
+ * between freeing and reassigning the context, our vsync
+ * interrupt will call into dc and cause a memory
+ * corruption BSOD. Hence, we first reassign the context,
+ * then free the old context.
+ */
+
struct validate_context *old = core_dc->current_context;
core_dc->current_context = context;