From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qk1-f201.google.com (mail-qk1-f201.google.com [209.85.222.201]) (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 B4F3330E0E5 for ; Tue, 21 Apr 2026 14:29:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.222.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776781789; cv=none; b=Bb1aHDBXHji6ZuD1jslvGZpnCeIMLPSj9NjCgzX0TCQ9vJSW62uwBeyhyBqUBaTzvQ2iy6lNxBzl2129uGB/F+j49UUmII3gQPwmQu3vGLNFDt2DqeNyMN2GY2571ZfJ1q+S8ZOQ6QxMFwWaZvqbvxCVKBN0uTdhtDGCxPtBbsM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776781789; c=relaxed/simple; bh=0sVBQdXKRDkJSG8meZQ/pBjSftRkZl7LQGy0n05ApBA=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=OrWoSfhzpzBvVGWxrYHlWaWPYeFJhpEezb561IxovGON7pfOO8pNiQnlfS3doIHELSRUI0qla0opcVqAvXMnsRek41QdTnqEwTB7/A9RiiXTXIJPxINVBue26hPaAGxR6wr7WLSfXTAJ3mZCQbs9LxCzOpH5HkapSWld2ofvc5U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--edumazet.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=iCyDKbVn; arc=none smtp.client-ip=209.85.222.201 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--edumazet.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="iCyDKbVn" Received: by mail-qk1-f201.google.com with SMTP id af79cd13be357-8cb6291d95aso718344185a.1 for ; Tue, 21 Apr 2026 07:29:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1776781787; x=1777386587; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=jvck/XoB8H/Wh1zgGi1810Si1lrAtzcUaSDMkL0ZmR0=; b=iCyDKbVnSZKP44mK/zS7LiAbUlkCX1o+phS1n/fq+aB/DjscTJ/IwYfLT3lE+C2IJu 7dWW/3EfHUIWX3cEKXkYYHFUVijlOjw8CcDHgLcNjU3TIAvbyTfx77jfcUDUEvgQacer vFC/xwCARWv/ByLedR9VK7itsDMrZOUBgLtoo3nsEjni9oM3+93QOMyL08cDpgsDZvuO wX2/UROuh0W6TXgi/Sigc+Rv5JQC8aDB0uXyUdEmBfv02YxT7CVGzyj0ee5Z8tZe6r/J jtz6ta4TB2op48kW5Xkv0/h/6oQ2EoqJxvSovTHE7T4igjNbp5UtG+EJZE4BPrQK8vch XhZg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1776781787; x=1777386587; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=jvck/XoB8H/Wh1zgGi1810Si1lrAtzcUaSDMkL0ZmR0=; b=rlQ/jqe6rOovX7F11XvWDQ4A5KP36FA3iu1pSbGptR/13lz3cL04yqsf6f1dlvpxwd leehqqTqjVLyMrvEHVFylOs56DOJDX7Fw/xsphB/B5llJtghKlwn29DCgBnmEe/U7v+8 sT3l5Fl7Qxemg2jIO8O+wG2WIfV6Fh2CVjptacK1D/GKWSxBczusOvaQlV880zNgpZT/ f4yfCtkoh0QD0/lYQ8JdCYOKFaA3mYDrHTv1NbPOuWDPMUKwmXUnJizbYKr9e9NQMAa0 xYKnJe4qwp5hC8k4XgMazAFZ/c9YaNzYAsiKiZXMhJDvFEhgcgznGfLv0gF78lnW+iXS NXnw== X-Forwarded-Encrypted: i=1; AFNElJ/Ke7vAwR/nnA8Gd5vlStul52yzWyVgcNgo4W/fBziy/qeFXFEHHYXSFt8tlukQj7mANG+yD9I=@vger.kernel.org X-Gm-Message-State: AOJu0YzP9cRLXWDHo1nDUx9PM28tWzEa5/A9a+D76ioC+Y1MWZB22V+J wM5ml+hq2Mjv69zouCZsO5n8FGu7aTaoaXeyzNLI2HNDrGg8zSbV9kEUPZ3DB28ZF/v2wrnpR+u sOjjGE8rhQlhtqg== X-Received: from qkjw1.prod.google.com ([2002:a05:620a:1481:b0:8cd:8ec2:8228]) (user=edumazet job=prod-delivery.src-stubby-dispatcher) by 2002:a05:620a:3720:b0:8cf:dfc9:c09c with SMTP id af79cd13be357-8e78f253c25mr2697155385a.10.1776781786327; Tue, 21 Apr 2026 07:29:46 -0700 (PDT) Date: Tue, 21 Apr 2026 14:29:44 +0000 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.54.0.rc2.533.g4f5dca5207-goog Message-ID: <20260421142944.4009941-1-edumazet@google.com> Subject: [PATCH net] net/sched: sch_pie: annotate data-races in pie_dump_stats() From: Eric Dumazet To: "David S . Miller" , Jakub Kicinski , Paolo Abeni Cc: Simon Horman , Jamal Hadi Salim , Jiri Pirko , netdev@vger.kernel.org, eric.dumazet@gmail.com, Eric Dumazet Content-Type: text/plain; charset="UTF-8" pie_dump_stats() only runs with RTNL held, reading fields that can be changed in qdisc fast path. Add READ_ONCE()/WRITE_ONCE() annotations. Alternative would be to acquire the qdisc spinlock, but our long-term goal is to make qdisc dump operations lockless as much as we can. tc_pie_xstats fields don't need to be latched atomically, otherwise this bug would have been caught earlier. Fixes: edb09eb17ed8 ("net: sched: do not acquire qdisc spinlock in qdisc/class stats dump") Signed-off-by: Eric Dumazet Reviewed-by: Jamal Hadi Salim --- include/net/pie.h | 2 +- net/sched/sch_pie.c | 38 +++++++++++++++++++------------------- 2 files changed, 20 insertions(+), 20 deletions(-) diff --git a/include/net/pie.h b/include/net/pie.h index 01cbc66825a40bd21c0a044b1180cbbc346785df..1f3db0c355149b41823a891c9156cac625122031 100644 --- a/include/net/pie.h +++ b/include/net/pie.h @@ -104,7 +104,7 @@ static inline void pie_vars_init(struct pie_vars *vars) vars->dq_tstamp = DTIME_INVALID; vars->accu_prob = 0; vars->dq_count = DQCOUNT_INVALID; - vars->avg_dq_rate = 0; + WRITE_ONCE(vars->avg_dq_rate, 0); } static inline struct pie_skb_cb *get_pie_cb(const struct sk_buff *skb) diff --git a/net/sched/sch_pie.c b/net/sched/sch_pie.c index 16f3f629cb8e4be71431f7e50a278e3c7fdba8d0..fb53fbf0e328571be72b66ba4e75a938e1963422 100644 --- a/net/sched/sch_pie.c +++ b/net/sched/sch_pie.c @@ -90,7 +90,7 @@ static int pie_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch, bool enqueue = false; if (unlikely(qdisc_qlen(sch) >= sch->limit)) { - q->stats.overlimit++; + WRITE_ONCE(q->stats.overlimit, q->stats.overlimit + 1); goto out; } @@ -104,7 +104,7 @@ static int pie_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch, /* If packet is ecn capable, mark it if drop probability * is lower than 10%, else drop it. */ - q->stats.ecn_mark++; + WRITE_ONCE(q->stats.ecn_mark, q->stats.ecn_mark + 1); enqueue = true; } @@ -114,15 +114,15 @@ static int pie_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch, if (!q->params.dq_rate_estimator) pie_set_enqueue_time(skb); - q->stats.packets_in++; + WRITE_ONCE(q->stats.packets_in, q->stats.packets_in + 1); if (qdisc_qlen(sch) > q->stats.maxq) - q->stats.maxq = qdisc_qlen(sch); + WRITE_ONCE(q->stats.maxq, qdisc_qlen(sch)); return qdisc_enqueue_tail(skb, sch); } out: - q->stats.dropped++; + WRITE_ONCE(q->stats.dropped, q->stats.dropped + 1); q->vars.accu_prob = 0; return qdisc_drop_reason(skb, sch, to_free, reason); } @@ -267,11 +267,11 @@ void pie_process_dequeue(struct sk_buff *skb, struct pie_params *params, count = count / dtime; if (vars->avg_dq_rate == 0) - vars->avg_dq_rate = count; + WRITE_ONCE(vars->avg_dq_rate, count); else - vars->avg_dq_rate = + WRITE_ONCE(vars->avg_dq_rate, (vars->avg_dq_rate - - (vars->avg_dq_rate >> 3)) + (count >> 3); + (vars->avg_dq_rate >> 3)) + (count >> 3)); /* If the queue has receded below the threshold, we hold * on to the last drain rate calculated, else we reset @@ -381,7 +381,7 @@ void pie_calculate_probability(struct pie_params *params, struct pie_vars *vars, if (delta > 0) { /* prevent overflow */ if (vars->prob < oldprob) { - vars->prob = MAX_PROB; + WRITE_ONCE(vars->prob, MAX_PROB); /* Prevent normalization error. If probability is at * maximum value already, we normalize it here, and * skip the check to do a non-linear drop in the next @@ -392,7 +392,7 @@ void pie_calculate_probability(struct pie_params *params, struct pie_vars *vars, } else { /* prevent underflow */ if (vars->prob > oldprob) - vars->prob = 0; + WRITE_ONCE(vars->prob, 0); } /* Non-linear drop in probability: Reduce drop probability quickly if @@ -403,7 +403,7 @@ void pie_calculate_probability(struct pie_params *params, struct pie_vars *vars, /* Reduce drop probability to 98.4% */ vars->prob -= vars->prob / 64; - vars->qdelay = qdelay; + WRITE_ONCE(vars->qdelay, qdelay); vars->backlog_old = backlog; /* We restart the measurement cycle if the following conditions are met @@ -502,21 +502,21 @@ static int pie_dump_stats(struct Qdisc *sch, struct gnet_dump *d) struct pie_sched_data *q = qdisc_priv(sch); struct tc_pie_xstats st = { .prob = q->vars.prob << BITS_PER_BYTE, - .delay = ((u32)PSCHED_TICKS2NS(q->vars.qdelay)) / + .delay = ((u32)PSCHED_TICKS2NS(READ_ONCE(q->vars.qdelay))) / NSEC_PER_USEC, - .packets_in = q->stats.packets_in, - .overlimit = q->stats.overlimit, - .maxq = q->stats.maxq, - .dropped = q->stats.dropped, - .ecn_mark = q->stats.ecn_mark, + .packets_in = READ_ONCE(q->stats.packets_in), + .overlimit = READ_ONCE(q->stats.overlimit), + .maxq = READ_ONCE(q->stats.maxq), + .dropped = READ_ONCE(q->stats.dropped), + .ecn_mark = READ_ONCE(q->stats.ecn_mark), }; /* avg_dq_rate is only valid if dq_rate_estimator is enabled */ st.dq_rate_estimating = q->params.dq_rate_estimator; /* unscale and return dq_rate in bytes per sec */ - if (q->params.dq_rate_estimator) - st.avg_dq_rate = q->vars.avg_dq_rate * + if (st.dq_rate_estimating) + st.avg_dq_rate = READ_ONCE(q->vars.avg_dq_rate) * (PSCHED_TICKS_PER_SEC) >> PIE_SCALE; return gnet_stats_copy_app(d, &st, sizeof(st)); -- 2.54.0.rc2.533.g4f5dca5207-goog