From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f201.google.com (mail-pl1-f201.google.com [209.85.214.201]) (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 E4EA7219303 for ; Thu, 23 Apr 2026 01:26:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776907588; cv=none; b=Y1BmTc1EmFCU3jeWaSdgWe/T3ORK7n18Q4N4L7RLjHf7G3f8MfyV755A8ozQxx8XqPVEqZGbwqdrlzfVxEiHhiM3CvX3r8sbeXoKf5iJV5+dRo5pYCfnY2eIHPpwlWCt9zefgZWKw4janKaIV1Ir128O+K21/5t9lKI9BgbaqoU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776907588; c=relaxed/simple; bh=38ygI611/cZr81uZTau/J3OdOllPwcSbiwlV4VAuy1A=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=QMlq1HmzYB3CJ/niIUS6xLcnIkGg0yd1ulV06H6EnAGpg1N4Y0TwlwUT/RAi+RtCuvT7ytS1aEl5lQqo+PJ2GJdaDlPwTVvBqPNFmmRa83uq/gXFySSqri8rlW3gryJwctNTQegCQ5WqCG2gwoUe8A8Kbm3S5cYgr6qBlCVCRhQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--jstultz.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=ZrUJxbhW; arc=none smtp.client-ip=209.85.214.201 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--jstultz.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="ZrUJxbhW" Received: by mail-pl1-f201.google.com with SMTP id d9443c01a7336-2b24cd2e2b3so57234525ad.0 for ; Wed, 22 Apr 2026 18:26:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1776907586; x=1777512386; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=a1iYRsPBV1u1X550LvvoKYrPaq03SnhZdHv11Z08TPk=; b=ZrUJxbhWbqmRLdbS+P4tWNAJs7SV3xM4Os8VUVJBK9COsa9bKCSQdK470EYuKSup6w W40ll69+NmHR/YtBLOMBX9hdEU+IA1lbEXX3AB+OBmym0aRYJpfMeIV+D79OW6TCqzcz 0tPReOjlyLAmXO0glERdaYbLa/cfUsjN3hSr7j0nDQHuOmLr6Uc4n8abKZW3pESHPp+z D9mj25ZJTqn9LflwpzSBTZZIpqGrnjaMJRjPLLctueoWxWs+Nr57pd+O9N3kJ9H4NEVV xbpGcKQm+QpowmdNoCqpW1h3CKzbjAcRKYjCEJ+13nw0CKVrjJiAGYRr+UbHcezuuA0U vRvw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1776907586; x=1777512386; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=a1iYRsPBV1u1X550LvvoKYrPaq03SnhZdHv11Z08TPk=; b=C4l3HFkyMYRYxtd2oEqpNs4SFDJp4g94aUfKbcW0mJfzz7YqSrM3FpuIMBVEy8RBaQ /MW6+I/PSu6l61IJuLQnGBtjQpcSXJ7/1mENDCi5I8dIke3uTFaaWypEh35wZ0w0Zb7D DL7JiblqFnRR5AiVM3x5/+3pqdS99p1tMfFWDKDA78U+qSgNBVmr3J0EWkYTeS5TV3hI FAcQSEbYSh/ds7tof/0eGO1wsPBczZgr3lYxgtwVQFe4adoDu5Xw4SKAcUq4e9VjcVWU ByFfRCeDg1zn/ctx2p+pVs8YohGupf0hACrIKZdCirCpMmycforhQfd2C6Zi5SXAIlJB iIiQ== X-Gm-Message-State: AOJu0Yy4qyGagwOfcj0n5VdJBkYmunGz4uB2RNcz6GPvI5UV+IPvGl4j sxsWSqTH19eYc+Z5DN61ZbNczrdpZZf/2phxgnNCuBHBKFNw4Uh2+MtaRSZqxl87wTyYMbd4o7P CpE/5TZoXTqTDt+J8uzju8czjLI6plHY738etEh8R61TPOtOV0BdlS99vW0NAFnWQfnuTO7KeXx frcul7a3KVy8yPqir8GoOaBm+NpmtHfb4FFeSlfYgH X-Received: from plbjw21.prod.google.com ([2002:a17:903:2795:b0:2b2:5616:36aa]) (user=jstultz job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:f645:b0:2ae:5163:c2aa with SMTP id d9443c01a7336-2b5f9f519e5mr247784565ad.20.1776907585932; Wed, 22 Apr 2026 18:26:25 -0700 (PDT) Date: Thu, 23 Apr 2026 01:26:16 +0000 Precedence: bulk X-Mailing-List: stable@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: <20260423012619.980559-1-jstultz@google.com> Subject: [PATCH 6.18] sched/debug: Fix avg_vruntime() usage From: John Stultz To: stable@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Vincent Guittot , K Prateek Nayak Content-Type: text/plain; charset="UTF-8" From: Peter Zijlstra commit e08d007f9d813616ce7093600bc4fdb9c9d81d89 upstream. John reported that stress-ng-yield could make his machine unhappy and managed to bisect it to commit b3d99f43c72b ("sched/fair: Fix zero_vruntime tracking"). The commit in question changes avg_vruntime() from a function that is a pure reader, to a function that updates variables. This turns an unlocked sched/debug usage of this function from a minor mistake into a data corruptor. Fixes: af4cf40470c2 ("sched/fair: Add cfs_rq::avg_vruntime") Fixes: b3d99f43c72b ("sched/fair: Fix zero_vruntime tracking") Reported-by: John Stultz Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Vincent Guittot Tested-by: K Prateek Nayak Tested-by: John Stultz Link: https://patch.msgid.link/20260401132355.196370805@infradead.org Signed-off-by: John Stultz --- kernel/sched/debug.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index 93f009e1076d8..3504ec9bd7307 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -798,6 +798,7 @@ static void print_rq(struct seq_file *m, struct rq *rq, int rq_cpu) void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq) { s64 left_vruntime = -1, zero_vruntime, right_vruntime = -1, left_deadline = -1, spread; + u64 avruntime; struct sched_entity *last, *first, *root; struct rq *rq = cpu_rq(cpu); unsigned long flags; @@ -821,6 +822,7 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq) if (last) right_vruntime = last->vruntime; zero_vruntime = cfs_rq->zero_vruntime; + avruntime = avg_vruntime(cfs_rq); raw_spin_rq_unlock_irqrestore(rq, flags); SEQ_printf(m, " .%-30s: %Ld.%06ld\n", "left_deadline", @@ -830,7 +832,7 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq) SEQ_printf(m, " .%-30s: %Ld.%06ld\n", "zero_vruntime", SPLIT_NS(zero_vruntime)); SEQ_printf(m, " .%-30s: %Ld.%06ld\n", "avg_vruntime", - SPLIT_NS(avg_vruntime(cfs_rq))); + SPLIT_NS(avruntime)); SEQ_printf(m, " .%-30s: %Ld.%06ld\n", "right_vruntime", SPLIT_NS(right_vruntime)); spread = right_vruntime - left_vruntime; -- 2.54.0.rc2.533.g4f5dca5207-goog