Received: by 2002:a25:8b91:0:0:0:0:0 with SMTP id j17csp4795267ybl; Tue, 4 Feb 2020 02:04:11 -0800 (PST) X-Google-Smtp-Source: APXvYqwidLcZM8irla8wBdFyyPOo1SKaCkmMCWZ9ibI5apmTvGgcwESbDNsMKYDYx+pT7PWZW0k1 X-Received: by 2002:a9d:5e82:: with SMTP id f2mr10590638otl.240.1580810651575; Tue, 04 Feb 2020 02:04:11 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1580810651; cv=none; d=google.com; s=arc-20160816; b=q7hYui/M4YZQ+YBbQZ1QoR6dtzr4kSXqbnMUECaPf7Gxmr6XloS3FFcHlTMVFWoCSd c2fT1bWvNuEu7dkMeBxzBkyL8nTln3JMex4RMKX6APhUrPWRz+iFJXwk38U10Mhmz69s ILVd1hpigpsspdKg4tc/i4uFZ7lvQmYN/sUgh5wt/K+UkG8sJDcLXtPUViZdQ8U3q+fG pxzg7m7ruDAoLdEnDMbfHkMWsCbCjADaHVo0oNCqsh4fCjvQUwKlLSsyQ6yYeSKnOYoP AZwEmISUITd/64+bbxdN4PtOv+77RAdff5iJY7wIDeKoeiUfjfb3Rqb+2mlyzikEx6eR WRLw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:content-transfer-encoding:mime-version :references:in-reply-to:message-id:subject:cc:to:from:date; bh=DaY22t7mPBaAzizah8FPUElTLnktDsau3EvwR54+LBo=; b=EA7VK+oNoniBMkA7ZvfDXI+Sq1mwO1dscBgTXDOrStoPepwm9Eo2xBYaKtzRBzjN+6 m+EqHY0p0hda7k89El5dFltWmuqppxoehwI2QrOlCtOrnJ6QUR0/rLoiOe3xnRCPZbl1 jyCb0xf8FAA1rqA1YczUZN+QxC4hBzuQFUQbb5js5kS9iFHK+8T0Xo2GIE4/PpgGzE5R Syu/7m0+Ne2+qTJDcvf3XIGlZ6QcyqV8nAouV1OYf5ObplV/Or1/AdZGzkelYDDaVUjP EoKcFKfvx3uXpuT0j/NeCACt3expZqXD38a1KSryScO1Y7iOmAvR2NpY4O3se8p/fRRa Oq9g== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id p13si11502686otq.210.2020.02.04.02.03.57; Tue, 04 Feb 2020 02:04:11 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726706AbgBDKCg (ORCPT + 99 others); Tue, 4 Feb 2020 05:02:36 -0500 Received: from mail.kernel.org ([198.145.29.99]:39402 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726343AbgBDKCg (ORCPT ); Tue, 4 Feb 2020 05:02:36 -0500 Received: from oasis.local.home (unknown [212.187.182.162]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 09C85217BA; Tue, 4 Feb 2020 10:02:33 +0000 (UTC) Date: Tue, 4 Feb 2020 05:02:29 -0500 From: Steven Rostedt To: Joel Fernandes Cc: Amol Grover , Ingo Molnar , linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linuxfoundation.org, Madhuparna Bhowmik , "Paul E . McKenney" Subject: Re: [PATCH] tracing: Annotate ftrace_graph_hash pointer with __rcu Message-ID: <20200204050229.70e2cb0e@oasis.local.home> In-Reply-To: <20200203163301.GB85781@google.com> References: <20200201072703.17330-1-frextrite@gmail.com> <20200203163301.GB85781@google.com> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 3 Feb 2020 11:33:01 -0500 Joel Fernandes wrote: > > preempt_disable_notrace(); > > > > - if (ftrace_hash_empty(ftrace_graph_hash)) { > > + hash = rcu_dereference_protected(ftrace_graph_hash, !preemptible()); > > I think you can use rcu_dereference_sched() here? That way no need to pass > !preemptible. > > A preempt-disabled section is an RCU "sched flavor" section. Flavors are > consolidated in the backend, but in the front end the dereference API still > do have flavors. Agreed, Amol, can you send an update? -- Steve