From nobody Mon Feb 9 17:57:56 2026 Received: from smtp2.math.uni-bielefeld.de (smtp2.math.uni-bielefeld.de [129.70.45.13]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9570818661C for ; Mon, 2 Sep 2024 09:42:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=129.70.45.13 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725270168; cv=none; b=EfoU7wae0Y8CoU/ftkJ33DcqPd0QymB26bhYg1HDlngVE8x/AShktnSjzUrnXbO6w4xC9+Pjpo3+t/0CXYb52XP9bykU+0Fk23t6S2/UoLP2Rw+SeQzkiYKKl3PaODbrzjTfKhPrZOCi6i2HvnJCQ1V6ufzxIZXYeNfcQQZW/rQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725270168; c=relaxed/simple; bh=OlHUmE2mWnpkfcvXYamxHN5q0GeOY6PdRc6d9KkwM28=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=cLc/Dex3OqRKm+esZsBrPXvwPtJqy039UYwQMWn3YmkgFjVHlkwCFHGCy1O9cblLvplg3081Huhz2ghNmuLOsDT/LwibyYpvq4O/T1zZGuhu/A89Cq+1cEWDWL/2EyAg0dU3t4hxhywSvG70un/aWH4348Hu7z4JD2jv4rAfA2o= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=math.uni-bielefeld.de; spf=pass smtp.mailfrom=math.uni-bielefeld.de; dkim=pass (2048-bit key) header.d=math.uni-bielefeld.de header.i=@math.uni-bielefeld.de header.b=PxhobTo3; arc=none smtp.client-ip=129.70.45.13 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=math.uni-bielefeld.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=math.uni-bielefeld.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=math.uni-bielefeld.de header.i=@math.uni-bielefeld.de header.b="PxhobTo3" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=math.uni-bielefeld.de; s=default; t=1725270163; bh=OlHUmE2mWnpkfcvXYamxHN5q0GeOY6PdRc6d9KkwM28=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PxhobTo34c9OgoeDCdYgmwTNIlFUqpQKQOEl5R38TVuQv6lAQOLtWcgesSMA5mqK3 /Pcll18vAVcyeKzuD2cegIT/of0J1un6UNsMsnozrwQ/XRC6PFovPmhRi44ktLpQJC 0/ci/Idbi5rtewd/c3+g44D5Ee6g7Y+ahRF/+okViVJo2YrdX2DLeKcOYkWUkglAIo zTERcuBa0RgZzInmUWcj37oE7pcUQDBK3YCAYyGbDragDLGzP+CmhoqM4NafskuFR2 Ax0GGBc0wjpSmsgSx5W3XOu9EAzH3BQhXeHzEwDK7/cc2owFWRCeO4xT4XFBZSO/Cw F2oTmHvU4RvzA== Received: from localhost (dslb-088-074-203-146.088.074.pools.vodafone-ip.de [88.74.203.146]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (prime256v1) server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by smtp2.math.uni-bielefeld.de (Postfix) with ESMTPSA id 7603B2098B; Mon, 2 Sep 2024 11:42:43 +0200 (CEST) From: tjakobi@math.uni-bielefeld.de To: Harry Wentland , Leo Li , Rodrigo Siqueira , Alex Deucher , =?UTF-8?q?Christian=20K=C3=B6nig?= , "Pan, Xinhui" , David Airlie , Daniel Vetter , Mario Limonciello Cc: Tobias Jakobi , amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: [PATCH 2/2] drm/amd/display: Avoid race between dcn35_set_drr() and dc_state_destruct() Date: Mon, 2 Sep 2024 11:40:27 +0200 Message-ID: X-Mailer: git-send-email 2.44.2 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Tobias Jakobi 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: 06ad7e164256 ("drm/amd/display: Destroy DC context while keeping DML= and DML2") Signed-off-by: Tobias Jakobi Reviewed-by: Harry Wentland --- .../amd/display/dc/hwss/dcn35/dcn35_hwseq.c | 20 +++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) diff --git a/drivers/gpu/drm/amd/display/dc/hwss/dcn35/dcn35_hwseq.c b/driv= ers/gpu/drm/amd/display/dc/hwss/dcn35/dcn35_hwseq.c index dcced89c07b3..4e77728dac10 100644 --- a/drivers/gpu/drm/amd/display/dc/hwss/dcn35/dcn35_hwseq.c +++ b/drivers/gpu/drm/amd/display/dc/hwss/dcn35/dcn35_hwseq.c @@ -1370,7 +1370,13 @@ void dcn35_set_drr(struct pipe_ctx **pipe_ctx, params.vertical_total_mid_frame_num =3D adjust.v_total_mid_frame_num; =20 for (i =3D 0; i < num_pipes; i++) { - if ((pipe_ctx[i]->stream_res.tg !=3D 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 =3D pipe_ctx[i]->stream_res.tg; + + if ((tg !=3D NULL) && tg->funcs) { struct dc_crtc_timing *timing =3D &pipe_ctx[i]->stream->timing; struct dc *dc =3D pipe_ctx[i]->stream->ctx->dc; =20 @@ -1383,14 +1389,12 @@ void dcn35_set_drr(struct pipe_ctx **pipe_ctx, num_frames =3D 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, ¶ms); + if (tg->funcs->set_drr) + tg->funcs->set_drr(tg, ¶ms); if (adjust.v_total_max !=3D 0 && adjust.v_total_min !=3D 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); } } } --=20 2.44.2