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 B1FE921576E; Mon, 27 Oct 2025 19:16:28 +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=1761592588; cv=none; b=cJNOOGOnzw88Q9hD3mHsJBhZtXfP4pae10bZVhOT63qbLBbGm58QvPObwqYmGuq+nv/yTXwWn1wFverARepsEp53i8MdHjgYTREJ7Gtz3rD2MzpN17f1zyAv2mGllrY20xmxtHKgmkxRoAv9Mj3z+92qExukxAPWe7LDYccbvj0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761592588; c=relaxed/simple; bh=Kr3hva3pd1vaqanO3yS5gs/OKbamIjnF84r7ZZejaJo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Qrvdm7zOtg6v8tHIZrQ4GX07bebaiLSiUUc2Co5decpuslX/8DAwVN4S9Du7obUcft5+t6ZCXXiQiKb5ZezikTz5zK3ylCv0FycKqNIQFNV2OptMivrf12X69LkQsx+TX97iond+VmSp1nXB3dkDG1BQhEww4uAS/bPPUIYKRcY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=tyLgoNQe; 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="tyLgoNQe" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2007DC4CEFD; Mon, 27 Oct 2025 19:16:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1761592588; bh=Kr3hva3pd1vaqanO3yS5gs/OKbamIjnF84r7ZZejaJo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tyLgoNQeP7i8WbeEaDyHqxQFDsAjYgyTQmyQmbl9bscu1tOXs6a/h+rgOdrfcIH6i TFSD2BNM0zj4PF2QRfjm+m33YYkG/O5Xk+/jBu/iJ5vYPauqyQWGpzpQ2A0hC7Rk3f j2IDrk4UYnnZ6DMIRvNnxHQezDiDJAg/WIgZ8JgA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jianpeng Chang , Wei Fang , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.6 20/84] net: enetc: fix the deadlock of enetc_mdio_lock Date: Mon, 27 Oct 2025 19:36:09 +0100 Message-ID: <20251027183439.359096896@linuxfoundation.org> X-Mailer: git-send-email 2.51.1 In-Reply-To: <20251027183438.817309828@linuxfoundation.org> References: <20251027183438.817309828@linuxfoundation.org> User-Agent: quilt/0.69 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 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jianpeng Chang [ Upstream commit 50bd33f6b3922a6b760aa30d409cae891cec8fb5 ] After applying the workaround for err050089, the LS1028A platform experiences RCU stalls on RT kernel. This issue is caused by the recursive acquisition of the read lock enetc_mdio_lock. Here list some of the call stacks identified under the enetc_poll path that may lead to a deadlock: enetc_poll -> enetc_lock_mdio -> enetc_clean_rx_ring OR napi_complete_done -> napi_gro_receive -> enetc_start_xmit -> enetc_lock_mdio -> enetc_map_tx_buffs -> enetc_unlock_mdio -> enetc_unlock_mdio After enetc_poll acquires the read lock, a higher-priority writer attempts to acquire the lock, causing preemption. The writer detects that a read lock is already held and is scheduled out. However, readers under enetc_poll cannot acquire the read lock again because a writer is already waiting, leading to a thread hang. Currently, the deadlock is avoided by adjusting enetc_lock_mdio to prevent recursive lock acquisition. Fixes: 6d36ecdbc441 ("net: enetc: take the MDIO lock only once per NAPI poll cycle") Signed-off-by: Jianpeng Chang Acked-by: Wei Fang Link: https://patch.msgid.link/20251015021427.180757-1-jianpeng.chang.cn@windriver.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- drivers/net/ethernet/freescale/enetc/enetc.c | 25 ++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-) diff --git a/drivers/net/ethernet/freescale/enetc/enetc.c b/drivers/net/ethernet/freescale/enetc/enetc.c index 49c61aa920b02..7accf3a3e9f0d 100644 --- a/drivers/net/ethernet/freescale/enetc/enetc.c +++ b/drivers/net/ethernet/freescale/enetc/enetc.c @@ -1246,6 +1246,8 @@ static int enetc_clean_rx_ring(struct enetc_bdr *rx_ring, /* next descriptor to process */ i = rx_ring->next_to_clean; + enetc_lock_mdio(); + while (likely(rx_frm_cnt < work_limit)) { union enetc_rx_bd *rxbd; struct sk_buff *skb; @@ -1281,7 +1283,9 @@ static int enetc_clean_rx_ring(struct enetc_bdr *rx_ring, rx_byte_cnt += skb->len + ETH_HLEN; rx_frm_cnt++; + enetc_unlock_mdio(); napi_gro_receive(napi, skb); + enetc_lock_mdio(); } rx_ring->next_to_clean = i; @@ -1289,6 +1293,8 @@ static int enetc_clean_rx_ring(struct enetc_bdr *rx_ring, rx_ring->stats.packets += rx_frm_cnt; rx_ring->stats.bytes += rx_byte_cnt; + enetc_unlock_mdio(); + return rx_frm_cnt; } @@ -1598,6 +1604,8 @@ static int enetc_clean_rx_ring_xdp(struct enetc_bdr *rx_ring, /* next descriptor to process */ i = rx_ring->next_to_clean; + enetc_lock_mdio(); + while (likely(rx_frm_cnt < work_limit)) { union enetc_rx_bd *rxbd, *orig_rxbd; int orig_i, orig_cleaned_cnt; @@ -1657,7 +1665,9 @@ static int enetc_clean_rx_ring_xdp(struct enetc_bdr *rx_ring, if (unlikely(!skb)) goto out; + enetc_unlock_mdio(); napi_gro_receive(napi, skb); + enetc_lock_mdio(); break; case XDP_TX: tx_ring = priv->xdp_tx_ring[rx_ring->index]; @@ -1692,7 +1702,9 @@ static int enetc_clean_rx_ring_xdp(struct enetc_bdr *rx_ring, } break; case XDP_REDIRECT: + enetc_unlock_mdio(); err = xdp_do_redirect(rx_ring->ndev, &xdp_buff, prog); + enetc_lock_mdio(); if (unlikely(err)) { enetc_xdp_drop(rx_ring, orig_i, i); rx_ring->stats.xdp_redirect_failures++; @@ -1712,8 +1724,11 @@ static int enetc_clean_rx_ring_xdp(struct enetc_bdr *rx_ring, rx_ring->stats.packets += rx_frm_cnt; rx_ring->stats.bytes += rx_byte_cnt; - if (xdp_redirect_frm_cnt) + if (xdp_redirect_frm_cnt) { + enetc_unlock_mdio(); xdp_do_flush(); + enetc_lock_mdio(); + } if (xdp_tx_frm_cnt) enetc_update_tx_ring_tail(tx_ring); @@ -1722,6 +1737,8 @@ static int enetc_clean_rx_ring_xdp(struct enetc_bdr *rx_ring, enetc_refill_rx_ring(rx_ring, enetc_bd_unused(rx_ring) - rx_ring->xdp.xdp_tx_in_flight); + enetc_unlock_mdio(); + return rx_frm_cnt; } @@ -1740,6 +1757,7 @@ static int enetc_poll(struct napi_struct *napi, int budget) for (i = 0; i < v->count_tx_rings; i++) if (!enetc_clean_tx_ring(&v->tx_ring[i], budget)) complete = false; + enetc_unlock_mdio(); prog = rx_ring->xdp.prog; if (prog) @@ -1751,10 +1769,8 @@ static int enetc_poll(struct napi_struct *napi, int budget) if (work_done) v->rx_napi_work = true; - if (!complete) { - enetc_unlock_mdio(); + if (!complete) return budget; - } napi_complete_done(napi, work_done); @@ -1763,6 +1779,7 @@ static int enetc_poll(struct napi_struct *napi, int budget) v->rx_napi_work = false; + enetc_lock_mdio(); /* enable interrupts */ enetc_wr_reg_hot(v->rbier, ENETC_RBIER_RXTIE); -- 2.51.0