From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 710A8318EC5; Thu, 1 Oct 2026 13:23:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790861040; cv=none; b=JBpmqXf+KCS1i3a1bccwpthMph3M+TYDWIi3vcy4IQGla/ps5Bhw9BJcZMwJ2VEWz/M5HKOMJrjwoiN+ciQJKFYe7YkoyaB5dYO2V54IPaK+6jlwHtBIDSajrioCtJg884FY6algOrknSWiwn6nW6+HU/xRLV8Pf3uzGLQKK3R0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790861040; c=relaxed/simple; bh=wDElpy/TGiRJSn/ziLR4CYi/go52QvZc+rz0PEQ7FBA=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=cuL+A0+XD3JTbZpdTDAJd8B6oAGP+JRx7jBr7P+VNg9AWlNmsmBio/nJgSs0MfGr15mt6sgN/O7KdVBGIxf+PzzMm/Qkw5a6ulNm15w5kOYi3on9+hFov/yotpt8b/8KARWHMvXri8eH8sGlFcfBYFWv9hNvOGBF2RIQBOVEIl0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KXYfjsEt; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="KXYfjsEt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EA95E1F000FF; Thu, 1 Oct 2026 13:23:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790861039; bh=DXB7tQcfmFfnugtQtf2FqJSIg4yqfN74RxF+rT3OIJ4=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=KXYfjsEtmBrjOHOpmGcZsAOnEve26Cv9qvbg/YdeO4N92M7jmsbdZHAQsV+evXOLC 9/d9FILtp4cVeZM2Mgv+dKbzN5EsCPootQDurWLu3KDuC2VI50uhLA0bNX/S3INOI7 Hu/kUs7lyr9lgJeHJ8+NfkGx9nD/pjgrwzZclVw4J9BwfBNSe+KFf7RI/PEWJikDak /S0yPrr7v6Tv5p0DBpjeOQ8luEk04CDL8AvlFy2mQEqDgamJh1dl6HR9Pab08V4w20 0CQLqE9ddLyPuDbW8lugUHOetzvCo2TIgA8hhbfT7AUNqB0GO+Kesc0MJp9lNvIOk8 kTbziUHvX2BrQ== Date: Thu, 1 Oct 2026 13:23:49 +0000 From: "Masami Hiramatsu (Google)" To: Steven Rostedt Cc: "Paul E . McKenney" , Frederic Weisbecker , Neeraj Upadhyay , Mathieu Desnoyers , Josef Bacik , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, rcu@vger.kernel.org Subject: Re: [PATCH] fprobe: Use guard(rcu_sched_notrace) and check rcu_is_watching() Message-ID: <20261001132349.472186a7@mhiramat99.roam.internal> In-Reply-To: <20260930160325.3f2621ea@fedora> References: <179064115227.394389.16910234241400391996.stgit@devnote2> <20260930160325.3f2621ea@fedora> X-Mailer: Claws Mail 4.4.0 (GTK 3.24.51; 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-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 30 Sep 2026 16:03:25 -0400 Steven Rostedt wrote: > On Tue, 29 Sep 2026 09:19:12 +0900 > "Masami Hiramatsu (Google)" wrote: > > > @@ -329,16 +333,14 @@ static void fprobe_ftrace_entry(unsigned long > > ip, unsigned long parent_ip, struct fprobe *fp; > > int bit; > > > > + if (!rcu_is_watching()) > > + return; > > + > > I'm thinking these should really be: > > if (WARN_ON_ONCE(!rcu_is_watching())) > return; Hmm, is this for warning users to notice it is out of supported path? If CONFIG_ARCH_WANTS_NO_INSTR=n, we will not prohibit user to set ftrace avoiding the function where the RCU is not watching. So maybe it is hit by user's operation. Thank you, > > -- Steve > -- Masami Hiramatsu (Google)