From mboxrd@z Thu Jan 1 00:00:00 1970 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 A5FD51F30AD; Thu, 17 Jul 2025 15:55:17 +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=1752767719; cv=none; b=VDoyxYD0rOM6gmU665rl70IulqetG0Q9mGPkVg9p2afUV6ZDkK+XjkcyY99LG5k1uB5tia4PQQTlsBUWt3/ooSyA/0SJrQRJfSEtX6DP1b/++ZfHXrHgS0DEwnVgBltItbI2h+dJ46W9/JBBeZAzENSFN87tBRwRRVCXyBdHqjU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752767719; c=relaxed/simple; bh=oU1gAGdpUX7HzDDDJ4fkE2E0mdxlsBu5BZtIWYhgpf4=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=fTGW2pSol2qVYF+wQ3hYcbo1PYak5EW/+PvQ8xJrtaIG91nwO5fd9eDOiVSHovSe/sblKQnA+kwC2xbt/EhqdsICyWcvPUDJ+vYgXhHTo5ZWklkNOlCfZfV/8/Ac/yZcSFuAeDdG5TvZy+8Q68PKK4v3SoTJLTQAfalzgNs4ptM= 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 omf04.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 29B261A014E; Thu, 17 Jul 2025 15:55:15 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf04.hostedemail.com (Postfix) with ESMTPA id 60B6520023; Thu, 17 Jul 2025 15:55:11 +0000 (UTC) Date: Thu, 17 Jul 2025 11:55:10 -0400 From: Steven Rostedt To: Alexei Starovoitov Cc: Mathieu Desnoyers , "Paul E. McKenney" , Sebastian Andrzej Siewior , Boqun Feng , linux-rt-devel@lists.linux.dev, rcu@vger.kernel.org, linux-trace-kernel , Frederic Weisbecker , Joel Fernandes , Josh Triplett , Lai Jiangshan , Masami Hiramatsu , Neeraj Upadhyay , Thomas Gleixner , Uladzislau Rezki , Zqiang , bpf Subject: Re: [RFC PATCH 1/2] rcu: Add rcu_read_lock_notrace() Message-ID: <20250717115510.7717f839@batman.local.home> In-Reply-To: <20250717114028.77ea7745@batman.local.home> References: <03083dee-6668-44bb-9299-20eb68fd00b8@paulmck-laptop> <29b5c215-7006-4b27-ae12-c983657465e1@efficios.com> <512331d8-fdb4-4dc1-8d9b-34cc35ba48a5@paulmck-laptop> <16dd7f3c-1c0f-4dfd-bfee-4c07ec844b72@paulmck-laptop> <20250716110922.0dadc4ec@batman.local.home> <895b48bd-d51e-4439-b5e0-0cddcc17a142@paulmck-laptop> <20250717111216.4949063d@batman.local.home> <20250717114028.77ea7745@batman.local.home> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: h6r9wbmd3dzzkdpunc95it6ceznsrrmj X-Rspamd-Server: rspamout05 X-Rspamd-Queue-Id: 60B6520023 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX1/HcqfUBq7ZAamlYZ+pbnUkiCl/Cr+nLwo= X-HE-Tag: 1752767711-221066 X-HE-Meta: U2FsdGVkX1/E7EZePk0SFBavuZDu4z0+Bq9q72Smix7XAoIfXqDza5uZhd1rIlUDnHUndKYZRRcFNvNLIxNuHI34ZtFbw+BHOhhBU1wLwkz2Yxure91zWHImZ17kPBo6N0HKqA9n04Pr1+gZZOui25GZstBF8Yq97+N04gWjRw9y1eS/KtK1P+OFve80pij7j4FAXpV0J23olv6XcUQs6GZ/bxoh471CbTy1jPLthlKCXPKR+VNUxx1GPjK44NBb5L0XPTw1TZaxQKXTYmRR2pNdVKT+2ORwk0uvlg3DGeapMRPgNfcCCVe/MsNNESf9E39cmtEspJhqVkNeSVtIDDRAhWtuetfznL3FUBq1J9ONPz6x0cLgH0g3YcMDLbTA On Thu, 17 Jul 2025 11:40:28 -0400 Steven Rostedt wrote: > Yes, it is a tracepoint infra problem that we are trying to solve. The > reason we are trying to solve it is because BPF programs can extend the > time a tracepoint takes. If anything else extended the time, this would > need to be solved as well. But currently it's only BPF programs that > cause the issue. BTW, if we can't solve this issue and something else came along and attached to tracepoints that caused unbounded latency, I would also argue that whatever came along would need to be prevented from being configured with PREEMPT_RT. My comment wasn't a strike against BPF programs; It was a strike against something adding unbounded latency into a critical section that has preemption disabled. -- Steve