From nobody Sun Feb 8 12:31:34 2026 Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) (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 2AA5B334694; Thu, 16 Oct 2025 17:28:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.12 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760635724; cv=none; b=V2/AFaCVtlk0lYrSXn8lJDbF9z0IdhRABfDUwO7IELM7FE1jKn/ILMmLecHy+dUYpQCFZRNkxCJaelTDig1DOEKW1H12iR875GvbHGZTQDcP17H301jJo/1Mj+KnBNjm8aId4fuCR6e2khV6tlWvJJcQaR6QUBSZ9Acfgc1hSlc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760635724; c=relaxed/simple; bh=R/q/AKN2X8TLTOQ+04qUt9yLcp9CCbLu8xq3N5p6yXo=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type; b=WXSnCeRnoA4mHkEeGaGIdGNWu1+wkoU2hpkrn/z3qeUttrWYISxVy57o7Jx3UJj3s7Qk7COnXbDg0Km5cJSXjkwzFX87xHYvcoQ6Tax821t/+S7HGoQkdvEa4cTTMPjwhs19xx45ngTaj8KHYYZUrtC6j4e67VmV00O26bZWjfo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org; spf=pass smtp.mailfrom=goodmis.org; arc=none smtp.client-ip=216.40.44.12 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Received: from omf07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id B7FDE1DFFC0; Thu, 16 Oct 2025 17:28:39 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf07.hostedemail.com (Postfix) with ESMTPA id 1069B20030; Thu, 16 Oct 2025 17:28:37 +0000 (UTC) Date: Thu, 16 Oct 2025 13:28:48 -0400 From: Steven Rostedt To: LKML , Linux Trace Kernel Cc: Masami Hiramatsu , Mathieu Desnoyers , Vincent Donnefort Subject: [PATCH] ring-buffer: Do not warn in ring_buffer_map_get_reader() when reader catches up Message-ID: <20251016132848.1b11bb37@gandalf.local.home> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Stat-Signature: jrtpowyrq4rwezqzezthq81roqzfrgix X-Rspamd-Server: rspamout03 X-Rspamd-Queue-Id: 1069B20030 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX19CXbz7v81C56kjBpRUdeWMNvKgDKnoavs= X-HE-Tag: 1760635717-439770 X-HE-Meta: U2FsdGVkX18Mrtb3j9AjBTGApz6ZsHMt0y6PVr3shpzIvHXVMudSXck/SZMExRm5CHXnXz9sdZrSl875wtC+awQnY71bHJkek7XfjfqJvTmUCgaH0JNHBgTQ1llsjS/LPbf65pUigkEfz6w3VeXuqAANu1ow2zSDAjUCsmeC6oNydFfHo0ZS3dkA/QCPdCtVEFmzRvgHrXXMVVapM8R4MGecVAUZ9M1LqKYIjAfJR19LOAE8+60JCEoRUpapOeih9Jji7Ub9TpD0sGwtXHmSIGg5stPLKbfDof1RFcpuITOu5coB7+k6rAHQ5XP95CYTY3/9eQJ/7d7ieZ3bVchyOq5sKXSwCfkGNrvvMpbYiaIAzhAalTnnPEIlI1UBk3VZWBjzhWN4S51aRwCypnNmzA== Content-Type: text/plain; charset="utf-8" From: Steven Rostedt The function ring_buffer_map_get_reader() is a bit more strict than the other get reader functions, and except for certain situations the rb_get_reader_page() should not return NULL. If it does, it triggers a warning. This warning was triggering but after looking at why, it was because another acceptable situation was happening and it wasn't checked for. If the reader catches up to the writer and there's still data to be read on the reader page, then the rb_get_reader_page() will return NULL as there's no new page to get. In this situation, the reader page should not be updated and no warning should trigger. Cc: stable@vger.kernel.org Fixes: 117c39200d9d7 ("ring-buffer: Introducing ring-buffer mapping functio= ns") Signed-off-by: Steven Rostedt (Google) --- kernel/trace/ring_buffer.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 1244d2c5c384..afcd3747264d 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -7344,6 +7344,10 @@ int ring_buffer_map_get_reader(struct trace_buffer *= buffer, int cpu) goto out; } =20 + /* Did the reader catch up with the writer? */ + if (cpu_buffer->reader_page =3D=3D cpu_buffer->commit_page) + goto out; + reader =3D rb_get_reader_page(cpu_buffer); if (WARN_ON(!reader)) goto out; --=20 2.51.0