From nobody Mon Dec 1 22:03:56 2025 Received: from mail-pf1-f202.google.com (mail-pf1-f202.google.com [209.85.210.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 08DB85695 for ; Thu, 27 Nov 2025 00:07:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764202077; cv=none; b=pGv8SMI+Iph4cjMTdUPnblKTc/LcWFpU1bFdyiXwwF5xUf3w0nkSglTOMn0EhfFC7g0XCmhHrLBSSMZVIM7RRFECOxHp23pEPC4bh9PbIZXghIsV2wlBbWfBIsK/VUlVqPWgNSU+Q2je0LHqBG4zYqfiw4fFux3mNL2qW6jei4o= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764202077; c=relaxed/simple; bh=PVwqPtohHLQR8u+q6aeUNdyYbu/y4oRVcTilsjce+Ko=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=AgcxMA+c5GPSNSvWTN1OXNDIR6KM+q9mUhrNU5xErpgv/CkqQ4bBZ6wkSbKSZyt6wjUXddPGVbjU5LRBQpXR70R+m4C4RFyqsOWRoQCOq6lKLh4MpyaW16hos2YVkvDhBafF85BhYhBs4RG6xBAJFUVFZtMilVy1lvJ37Mroyd4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--hramamurthy.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=LW00lKRJ; arc=none smtp.client-ip=209.85.210.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--hramamurthy.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="LW00lKRJ" Received: by mail-pf1-f202.google.com with SMTP id d2e1a72fcca58-7c7957d978aso229220b3a.1 for ; Wed, 26 Nov 2025 16:07:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1764202075; x=1764806875; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=dnKcf2+51kURgvBReSH5vkNuGQRyYKTVBdC22OlhFiE=; b=LW00lKRJCOD6broJZk7Pq8M2gSC4MrqhNlwmhzdH8V58SKBkpdSGZjmirZnoiui0tA m39d20pL1k0QwPXD8mdAZpKLiZC4tU2EYy0M8nidcJGMSVLT1Ft2cpgokAlLZnQZNLN1 9WHKobmlfKz73kZyDrCVhC0ZlreDJdRtYeNpfLvxymPNdyPY22iu2bA1eJR85f6ce2V9 6l2Za59AuQOtKv2Nl7q8cA/Vm7E3RQME6cQaAUDpFRSZjtMpFKp3/y09jMp9b1YALqe1 qCguFzSnx/E43O7eXppws+5ImOFl8kLiPv1on5WJDq33pccHSy5KHmpEXzefVwVfQMsW zh0g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1764202075; x=1764806875; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=dnKcf2+51kURgvBReSH5vkNuGQRyYKTVBdC22OlhFiE=; b=mD1UlOOo2SSLJuf4FXyAsquNS3vmP4MzCX5FYkGf7q2cOV8XwDFm5sMF/IXjC1OMa4 KaAwKSijRsKb/wgSeje7/KxB4QFXw0fuTb4hFvF3yuy+YtOZX0FGe0ys+/4f8OQfwNa8 dJotq5mrTVYW/81wVXvtDPbVCY1AdWDVBsgq5RCc2Zi4c4djSWmEmkZAYq9mybi3YGb1 A2gDPbJI902F3JCWNbySkwU3t/4iyTKSQvz/4g/bU0itjZ6NUuMRMG8fW3W3Mp6Iz5Tf +7mB6MO4WZm+RwUJMmppNbDr3GFWKlDZCGz+IJoTO3Ix7FiN3Y3vZZiWKZJVhG3z0viF t/bQ== X-Forwarded-Encrypted: i=1; AJvYcCWFytNAxyMKw3sNrSur+5T4cNcsI87q8+kuvIEZtnaG1a5lWupdMek0r7dCW9EUhwA49B4BBS2BjL4+Hpg=@vger.kernel.org X-Gm-Message-State: AOJu0Yxv8vHqT+W5xyLdVCeWjSyjQO3zjcOVai1nEfJpFsHSp/csfLxm M/QN2A6MWV6sfTdWnqPRPh73kjQhoPyN5KCvIW1IcMJvJBQ+Cd9PaVmNRGPicd2E2IkQ3f0kgnH th+k8JPkaKOzosrNWwqMUUWLK2A== X-Google-Smtp-Source: AGHT+IGnhmhMCtW2cqlbfM3z72gA3XlXtWRfaLc1b3OcMPSW0COKY++7leT3iMEM1SYLmLlnoSD7fB5Ar+eIczA8Pg== X-Received: from pfbfx22.prod.google.com ([2002:a05:6a00:8216:b0:7cf:2dad:ff8d]) (user=hramamurthy job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:9508:b0:7aa:93d5:820f with SMTP id d2e1a72fcca58-7c58e9f97bcmr22294145b3a.30.1764202075226; Wed, 26 Nov 2025 16:07:55 -0800 (PST) Date: Thu, 27 Nov 2025 00:07:51 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.52.0.487.g5c8c507ade-goog Message-ID: <20251127000751.662959-1-hramamurthy@google.com> Subject: [PATCH net-next] gve: Fix race condition on tx->dropped_pkt update From: Harshitha Ramamurthy To: netdev@vger.kernel.org Cc: joshwash@google.com, hramamurthy@google.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, willemb@google.com, pkaligineedi@google.com, linux-kernel@vger.kernel.org, Max Yuan , Jordan Rhee Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Max Yuan The tx->dropped_pkt counter is a 64-bit integer that is incremented directly. On 32-bit architectures, this operation is not atomic and can lead to read/write tearing if a reader accesses the counter during the update. This can result in incorrect values being reported for dropped packets. To prevent this potential data corruption, wrap the increment operation with u64_stats_update_begin() and u64_stats_update_end(). This ensures that updates to the 64-bit counter are atomic, even on 32-bit systems, by using a sequence lock. The u64_stats_sync API requires the writer to have exclusive access, which is already provided in this context by the network stack's serialization of the transmit path (net_device_ops::ndo_start_xmit [1]) for a given queue. [1]: https://www.kernel.org/doc/Documentation/networking/netdevices.txt Signed-off-by: Max Yuan Reviewed-by: Jordan Rhee Signed-off-by: Harshitha Ramamurthy --- drivers/net/ethernet/google/gve/gve_tx.c | 2 ++ drivers/net/ethernet/google/gve/gve_tx_dqo.c | 6 ++++++ 2 files changed, 8 insertions(+) diff --git a/drivers/net/ethernet/google/gve/gve_tx.c b/drivers/net/etherne= t/google/gve/gve_tx.c index c6ff0968929d..97efc8d27e6f 100644 --- a/drivers/net/ethernet/google/gve/gve_tx.c +++ b/drivers/net/ethernet/google/gve/gve_tx.c @@ -730,7 +730,9 @@ static int gve_tx_add_skb_no_copy(struct gve_priv *priv= , struct gve_tx_ring *tx, gve_tx_unmap_buf(tx->dev, &tx->info[idx & tx->mask]); } drop: + u64_stats_update_begin(&tx->statss); tx->dropped_pkt++; + u64_stats_update_end(&tx->statss); return 0; } =20 diff --git a/drivers/net/ethernet/google/gve/gve_tx_dqo.c b/drivers/net/eth= ernet/google/gve/gve_tx_dqo.c index 6f1d515673d2..40b89b3e5a31 100644 --- a/drivers/net/ethernet/google/gve/gve_tx_dqo.c +++ b/drivers/net/ethernet/google/gve/gve_tx_dqo.c @@ -1002,7 +1002,9 @@ static int gve_try_tx_skb(struct gve_priv *priv, stru= ct gve_tx_ring *tx, return 0; =20 drop: + u64_stats_update_begin(&tx->statss); tx->dropped_pkt++; + u64_stats_update_end(&tx->statss); dev_kfree_skb_any(skb); return 0; } @@ -1324,7 +1326,11 @@ static void remove_miss_completions(struct gve_priv = *priv, /* This indicates the packet was dropped. */ dev_kfree_skb_any(pending_packet->skb); pending_packet->skb =3D NULL; + + u64_stats_update_begin(&tx->statss); tx->dropped_pkt++; + u64_stats_update_end(&tx->statss); + net_err_ratelimited("%s: No reinjection completion was received for: %d.= \n", priv->dev->name, (int)(pending_packet - tx->dqo.pending_packets)); --=20 2.52.0.487.g5c8c507ade-goog