From patchwork Mon Sep 2 09:40:26 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Tobias Jakobi X-Patchwork-Id: 13786968 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 37447CA0ED3 for ; Mon, 2 Sep 2024 09:41:26 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id A4D1310E0CC; Mon, 2 Sep 2024 09:41:25 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; secure) header.d=math.uni-bielefeld.de header.i=@math.uni-bielefeld.de header.b="eG7RNFJf"; dkim-atps=neutral Received: from smtp2.math.uni-bielefeld.de (smtp2.math.uni-bielefeld.de [129.70.45.13]) by gabe.freedesktop.org (Postfix) with ESMTPS id 0C7FF10E279; Mon, 2 Sep 2024 09:41:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=math.uni-bielefeld.de; s=default; t=1725270082; bh=+zKyfDeG1O93W2ZvWeGRXFBv0Meg5VnoIPBsky28Bpg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eG7RNFJfRcvxTzXfiBR69eBsQBRQpchcrbMGUvo7uolU4X4ENc9XiqQUU/QU8UBuq PZ40uwkYSb3qM8MxqTSUoAA+EybrFX4fUhzCpxDgTKMt9VXl+qaWOaChiOUeBKWCeH krdHfGdRFKfMJm24J15ZC1ophquN/uXLsOfN/UbF4JYPM+qv64GQr4m8FLB+RGu14D YUNr/AMrIHtruT2UlH3OmBTpQ8ZtguwabV6UNgjD5fewzmCBYnO8xe1DWL+y2VveB8 QBPihzqzlSOwtAZqih89mVVCfQ2vjfFfoTx3upaZnHYQaEgddIM6DPwbRIlxQWD/Ld S/a9wc9B04oWA== 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 4CB9B206F4; Mon, 2 Sep 2024 11:41:22 +0200 (CEST) From: tjakobi@math.uni-bielefeld.de To: Harry Wentland , Leo Li , Rodrigo Siqueira , Alex Deucher , =?utf-8?q?Christian_K=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 1/2] drm/amd/display: Avoid race between dcn10_set_drr() and dc_state_destruct() Date: Mon, 2 Sep 2024 11:40:26 +0200 Message-ID: <7b9dbbbb1e6a3aa6d7a4d9367d44d18ddd947158.1725269643.git.tjakobi@math.uni-bielefeld.de> X-Mailer: git-send-email 2.44.2 In-Reply-To: References: MIME-Version: 1.0 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" From: Tobias Jakobi dc_state_destruct() nulls the resource context of the DC state. The pipe context passed to dcn10_set_drr() is a member of this resource context. If dc_state_destruct() is called parallel to the IRQ processing (which calls dcn10_set_drr() at some point), we can end up using already nulled function callback fields of struct stream_resource. The logic in dcn10_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 Tested-by: Sefa Eyeoglu Tested-by: Raoul van Rüschen Tested-by: Christopher Snowhill Reviewed-by: Harry Wentland --- .../amd/display/dc/hwss/dcn10/dcn10_hwseq.c | 20 +++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) diff --git a/drivers/gpu/drm/amd/display/dc/hwss/dcn10/dcn10_hwseq.c b/drivers/gpu/drm/amd/display/dc/hwss/dcn10/dcn10_hwseq.c index 3306684e805a..da8f2cb3c5db 100644 --- a/drivers/gpu/drm/amd/display/dc/hwss/dcn10/dcn10_hwseq.c +++ b/drivers/gpu/drm/amd/display/dc/hwss/dcn10/dcn10_hwseq.c @@ -3223,15 +3223,19 @@ void dcn10_set_drr(struct pipe_ctx **pipe_ctx, * as well. */ for (i = 0; i < num_pipes; i++) { - if ((pipe_ctx[i]->stream_res.tg != NULL) && pipe_ctx[i]->stream_res.tg->funcs) { - 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); + /* 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) { + if (tg->funcs->set_drr) + tg->funcs->set_drr(tg, ¶ms); 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); } } }