From: Corbin McElhanney <corbin.mcelhanney@amd.com>
Date: Wed, 9 Aug 2017 14:30:28 +0000 (-0400)
Subject: drm/amd/display: Add comment explaining context free
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=e771aae02baa59386972faec491cd221c169ed53;p=linux.git

drm/amd/display: Add comment explaining context free

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>
---

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc.c b/drivers/gpu/drm/amd/display/dc/core/dc.c
index 477024c467e63..33c3d88b1c866 100644
--- 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 dc *dc,
 	}
 
 	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;