From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 3A2EE1D959B; Tue, 25 Mar 2025 12:28:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742905695; cv=none; b=hvhkY5rkgAUB1BPx7WE56qQT2ZTNVo95MtUnCEuU1lMnWbcbvIEM/bYzozrKghl9dSxKL5wycUt93pgAZus+6Iie4tR2MhqfWZrOEo04J2HkEDABbGQ0+Qb4lBov2KvxaRnzU3U7sqpXCE9bczOMNc84fA6B0gMWJF02A5aE/vc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742905695; c=relaxed/simple; bh=rgqUWwmzXWUmT2TuHp41ynTWalCZsfbfzvqStFCYG+E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=t4y2Z/6CUoIW7MamTx68HLgBEquh+29Cp9qc9YwcAGCmRfWfG3SYYBW4qIwihvc4RiXrOw6Yy9UIAK7yGulea8U6uZnckIL55fITT91PBiYQ+m7H1d13wtl2L+DLplhGFi+5aoO6MzU0/8kiE6AxUZRMhxPTzKv3axLJEoOrGCk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Qg+oBuss; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Qg+oBuss" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E3759C4CEE4; Tue, 25 Mar 2025 12:28:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1742905695; bh=rgqUWwmzXWUmT2TuHp41ynTWalCZsfbfzvqStFCYG+E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Qg+oBuss9zazi2aKyP2wq60hsLtfqV3gSBKsXxCmb04mlOR8EaT4tV1mWMo2a3Hza dXPv6KmSHpKTpsdcO6Px38iOn4WYJisGj9a99295rG7uUB/gwZjP2nb3n8/1g9O28p 9EL6W2OhyQIcx/Dds14iLK+CV4WlGv5jsY6wbmbM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Wayne Lin , Lyude Paul , Imre Deak Subject: [PATCH 6.1 114/198] drm/dp_mst: Fix locking when skipping CSN before topology probing Date: Tue, 25 Mar 2025 08:21:16 -0400 Message-ID: <20250325122159.644876275@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250325122156.633329074@linuxfoundation.org> References: <20250325122156.633329074@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Imre Deak commit 12d8f318347b1d4feac48e8ac351d3786af39599 upstream. The handling of the MST Connection Status Notify message is skipped if the probing of the topology is still pending. Acquiring the drm_dp_mst_topology_mgr::probe_lock for this in drm_dp_mst_handle_up_req() is problematic: the task/work this function is called from is also responsible for handling MST down-request replies (in drm_dp_mst_handle_down_rep()). Thus drm_dp_mst_link_probe_work() - holding already probe_lock - could be blocked waiting for an MST down-request reply while drm_dp_mst_handle_up_req() is waiting for probe_lock while processing a CSN message. This leads to the probe work's down-request message timing out. A scenario similar to the above leading to a down-request timeout is handling a CSN message in drm_dp_mst_handle_conn_stat(), holding the probe_lock and sending down-request messages while a second CSN message sent by the sink subsequently is handled by drm_dp_mst_handle_up_req(). Fix the above by moving the logic to skip the CSN handling to drm_dp_mst_process_up_req(). This function is called from a work (separate from the task/work handling new up/down messages), already holding probe_lock. This solves the above timeout issue, since handling of down-request replies won't be blocked by probe_lock. Fixes: ddf983488c3e ("drm/dp_mst: Skip CSN if topology probing is not done yet") Cc: Wayne Lin Cc: Lyude Paul Cc: stable@vger.kernel.org # v6.6+ Reviewed-by: Wayne Lin Reviewed-by: Lyude Paul Signed-off-by: Imre Deak Link: https://patchwork.freedesktop.org/patch/msgid/20250307183152.3822170-1-imre.deak@intel.com Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/display/drm_dp_mst_topology.c | 40 +++++++++++++++----------- 1 file changed, 24 insertions(+), 16 deletions(-) --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c @@ -3959,6 +3959,22 @@ out: return 0; } +static bool primary_mstb_probing_is_done(struct drm_dp_mst_topology_mgr *mgr) +{ + bool probing_done = false; + + mutex_lock(&mgr->lock); + + if (mgr->mst_primary && drm_dp_mst_topology_try_get_mstb(mgr->mst_primary)) { + probing_done = mgr->mst_primary->link_address_sent; + drm_dp_mst_topology_put_mstb(mgr->mst_primary); + } + + mutex_unlock(&mgr->lock); + + return probing_done; +} + static inline bool drm_dp_mst_process_up_req(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_pending_up_req *up_req) @@ -3989,8 +4005,12 @@ drm_dp_mst_process_up_req(struct drm_dp_ /* TODO: Add missing handler for DP_RESOURCE_STATUS_NOTIFY events */ if (msg->req_type == DP_CONNECTION_STATUS_NOTIFY) { - dowork = drm_dp_mst_handle_conn_stat(mstb, &msg->u.conn_stat); - hotplug = true; + if (!primary_mstb_probing_is_done(mgr)) { + drm_dbg_kms(mgr->dev, "Got CSN before finish topology probing. Skip it.\n"); + } else { + dowork = drm_dp_mst_handle_conn_stat(mstb, &msg->u.conn_stat); + hotplug = true; + } } drm_dp_mst_topology_put_mstb(mstb); @@ -4069,10 +4089,11 @@ static int drm_dp_mst_handle_up_req(stru drm_dp_send_up_ack_reply(mgr, mst_primary, up_req->msg.req_type, false); + drm_dp_mst_topology_put_mstb(mst_primary); + if (up_req->msg.req_type == DP_CONNECTION_STATUS_NOTIFY) { const struct drm_dp_connection_status_notify *conn_stat = &up_req->msg.u.conn_stat; - bool handle_csn; drm_dbg_kms(mgr->dev, "Got CSN: pn: %d ldps:%d ddps: %d mcs: %d ip: %d pdt: %d\n", conn_stat->port_number, @@ -4081,16 +4102,6 @@ static int drm_dp_mst_handle_up_req(stru conn_stat->message_capability_status, conn_stat->input_port, conn_stat->peer_device_type); - - mutex_lock(&mgr->probe_lock); - handle_csn = mst_primary->link_address_sent; - mutex_unlock(&mgr->probe_lock); - - if (!handle_csn) { - drm_dbg_kms(mgr->dev, "Got CSN before finish topology probing. Skip it."); - kfree(up_req); - goto out_put_primary; - } } else if (up_req->msg.req_type == DP_RESOURCE_STATUS_NOTIFY) { const struct drm_dp_resource_status_notify *res_stat = &up_req->msg.u.resource_stat; @@ -4105,9 +4116,6 @@ static int drm_dp_mst_handle_up_req(stru list_add_tail(&up_req->next, &mgr->up_req_list); mutex_unlock(&mgr->up_req_lock); queue_work(system_long_wq, &mgr->up_req_work); - -out_put_primary: - drm_dp_mst_topology_put_mstb(mst_primary); out_clear_reply: memset(&mgr->up_req_recv, 0, sizeof(struct drm_dp_sideband_msg_rx)); return 0;