From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f72.google.com (mail-ej1-f72.google.com [209.85.218.72]) (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 B1F2948D88F for ; Wed, 29 Jul 2026 13:36:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.218.72 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785332186; cv=none; b=InAhGL7RUTCVRjLgmnso4ZVR2k8tvJgorHE4njy4L8czE47rtw5Qkq0uRexXX96LFrdIyqV2kG1h01YJxS9PHx5sQ49fWzbZmZ+UDohv5DxAGJBqzmKkqnYOS9xSUGNcyr1wlHV77myYivVjFbG9368VGQf8bfL24Leetbxa7po= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785332186; c=relaxed/simple; bh=V8KkWNEIL1EtblHKb3pRj3mDqxpGnxcUY2YFdefRDZ8=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=jldPEV8qUrkQEIrsIrlqAvPGMYYAMauO44ArucRqpBwwOq0jnnUpsKTFCA4nD8OwLgIJ1cwu5qFJ1MnwuZT99ZPxHCmSwrB5co4k1LjHBIGt62tae90lQ/biirt33s2wHomI17WbIwZu6218FxnJYHln16SHaiRI2bpe7gUhnZk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=nG9FNmDW; arc=none smtp.client-ip=209.85.218.72 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--vdonnefort.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="nG9FNmDW" Received: by mail-ej1-f72.google.com with SMTP id a640c23a62f3a-c15c32294e1so102872966b.3 for ; Wed, 29 Jul 2026 06:36:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1785332175; x=1785936975; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:mime-version:date:from :to:cc:subject:date:message-id:reply-to:content-type; bh=DqKEjFTGm7dqnB3Iuy8Yez/XkakkUBzOCNyU+fjpBRU=; b=nG9FNmDWSIdmkusARNQu0qExVNRo0PVo7xoci3dOMZah81RcENLfI0HhRIHJnaZagB 6GAdh//ednJTa1JX92aEYGLsOcNRmPlXkq34DBFK/fR1rc4R/kjhxwk/2x6LE4iGMwhC yN0y6WBup2tsko6eISV+7BKat0WY/3D1OUKGpwSsknyyby20L4G8cU0StMyPANMboWWv nSetJUaZqCykiynQAqjSOXBEk92kg/S3h2casDme8j+swiDHCNPc7IV+8PSbrQsBU5Da XKZk7t4Mm7dRjMoZYxBLj3pS0tgs7RUFf6mbvDwypjipUV/iQ1KBGCd1J4+rC5Omz7Ga k2TA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1785332175; x=1785936975; h=content-type:cc:to:from:subject:message-id:mime-version:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=DqKEjFTGm7dqnB3Iuy8Yez/XkakkUBzOCNyU+fjpBRU=; b=D/8vGnfccBkldwMpE9gLh7pffI8BWmCFnp7x35AVHbEkpVkA4/e8xseAvVVfAdUMpM QAgTqjY8TzYXqKphGHmKA8X3YBcTbEl2tRC1pKn3SWaAzgyKEwAwvk8Fr/nxo+kQpWRp unL6yYpjfC4Qmam0gVD6L72tOGfpDK8qlPgiP6VRmQgIQ58lWFzLcSqZrOY0GtPkMdCo dqfRQGTSIOx6dOQu14D6VpJlc6aW5SUEzJpHbRAtbciqhe88xdaNj058wkkwdXiTPfJ9 uClwxBkk4eCUs2R9dEqwzJ87bL22mPw3p8cYqoc8Dm492icBYqlMBJb/JWhe/rvAs+wB rEiw== X-Forwarded-Encrypted: i=1; AHgh+Rpo0yM16cS0Qrm6q3K+ql66QRB1IkKTYnvy3CP6WCLWUAFECivc0FBx8t5F9swXvNghuUYYVUiAXC9D6Pk=@vger.kernel.org X-Gm-Message-State: AOJu0YykYlN/ReQ+uX55wuubixy3UZAdC6ZvGscWX5vWyaKPd1S6t1LW Ug5nwCsc5QJaltTca6ZbNujKzPwDM9bqgDmCQBUJLxgYCi/Jc7L9Nf5C/Wn8kSUphZ6Pd+0gHhR fobn0U507LxeeQRLQmLafTA== X-Received: from ejcjv3.prod.google.com ([2002:a17:907:7683:b0:c1e:eadb:2ec]) (user=vdonnefort job=prod-delivery.src-stubby-dispatcher) by 2002:a17:907:e00c:10b0:c19:5d7c:ae72 with SMTP id a640c23a62f3a-c1f720ef123mr268508066b.32.1785332175379; Wed, 29 Jul 2026 06:36:15 -0700 (PDT) Date: Wed, 29 Jul 2026 14:36:09 +0100 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 2.55.0.487.gaf234c4eb3-goog Message-ID: <20260729133609.4022734-1-vdonnefort@google.com> Subject: [PATCH] ring-buffer: Fix reader page read offset for remote buffers From: Vincent Donnefort To: rostedt@goodmis.org, mhiramat@kernel.org, linux-trace-kernel@vger.kernel.org Cc: mathieu.desnoyers@efficios.com, kernel-team@android.com, linux-kernel@vger.kernel.org, keirf@google.com, Vincent Donnefort Content-Type: text/plain; charset="UTF-8" A page swapped in by __rb_get_reader_page_from_remote() retains its stale read offset, causing subsequent reads to skip events or read past valid data. Fix it. Fixes: fbd1743ecba1 ("ring-buffer: Add non-consuming read for ring-buffer remotes") Signed-off-by: Vincent Donnefort diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 804ccae694d2..78d3875a47a5 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -5783,6 +5783,7 @@ __rb_get_reader_page_from_remote(struct ring_buffer_per_cpu *cpu_buffer) cpu_buffer->head_page = new_head; cpu_buffer->reader_page = new_reader; + cpu_buffer->reader_page->read = 0; cpu_buffer->pages = &new_head->list; cpu_buffer->read_stamp = new_reader->page->time_stamp; cpu_buffer->lost_events = cpu_buffer->meta_page->reader.lost_events; base-commit: f5098b6bae761e346ebcd9da7f95622c04733cff -- 2.55.0.487.gaf234c4eb3-goog