Commit e835d514 authored by Tobias Jakobi's avatar Tobias Jakobi Committed by Alex Deucher
Browse files

drm/amd/display: Avoid race between dcn35_set_drr() and dc_state_destruct() 

dc_state_destruct() nulls the resource context of the DC state. The pipe
context passed to dcn35_set_drr() is a member of this resource context.

If dc_state_destruct() is called parallel to the IRQ processing (which
calls dcn35_set_drr() at some point), we can end up using already nulled
function callback fields of struct stream_resource.

The logic in dcn35_set_drr() already tries to avoid this, by checking tg
against NULL. But if the nulling happens exactly after the NULL check and
before the next access, then we get a race.

Avoid this by copying tg first to a local variable, and then use this
variable for all the operations. This should work, as long as nobody
frees the resource pool where the timing generators live.

Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3142


Fixes: 06ad7e16 ("drm/amd/display: Destroy DC context while keeping DML and DML2")
Signed-off-by: default avatarTobias Jakobi <tjakobi@math.uni-bielefeld.de>
Reviewed-by: default avatarHarry Wentland <harry.wentland@amd.com>
Signed-off-by: default avatarMario Limonciello <mario.limonciello@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 0607a50c)
Cc: stable@vger.kernel.org
parent a7aeb038

drivers/gpu/drm/amd/display/dc/hwss/dcn35/dcn35_hwseq.c

+12 −8
Original line number Diff line number Diff line
@@ -1462,7 +1462,13 @@ void dcn35_set_drr(struct pipe_ctx **pipe_ctx, 
	params.vertical_total_mid_frame_num = adjust.v_total_mid_frame_num;



	for (i = 0; i < num_pipes; i++) {

		if ((pipe_ctx[i]->stream_res.tg != NULL) && pipe_ctx[i]->stream_res.tg->funcs) {

		/* dc_state_destruct() might null the stream resources, so fetch tg

		 * here first to avoid a race condition. The lifetime of the pointee

		 * itself (the timing_generator object) is not a problem here.

		 */

		struct timing_generator *tg = pipe_ctx[i]->stream_res.tg;



		if ((tg != NULL) && tg->funcs) {

			struct dc_crtc_timing *timing = &pipe_ctx[i]->stream->timing;

			struct dc *dc = pipe_ctx[i]->stream->ctx->dc;
@@ -1475,14 +1481,12 @@ void dcn35_set_drr(struct pipe_ctx **pipe_ctx, 
					num_frames = 2 * (frame_rate % 60);

				}

			}

			if (pipe_ctx[i]->stream_res.tg->funcs->set_drr)

				pipe_ctx[i]->stream_res.tg->funcs->set_drr(

					pipe_ctx[i]->stream_res.tg, &params);

			if (tg->funcs->set_drr)

				tg->funcs->set_drr(tg, &params);

			if (adjust.v_total_max != 0 && adjust.v_total_min != 0)

				if (pipe_ctx[i]->stream_res.tg->funcs->set_static_screen_control)

					pipe_ctx[i]->stream_res.tg->funcs->set_static_screen_control(

						pipe_ctx[i]->stream_res.tg,

						event_triggers, num_frames);

				if (tg->funcs->set_static_screen_control)

					tg->funcs->set_static_screen_control(

						tg, event_triggers, num_frames);

		}

	}

}