From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-x441.google.com (mail-pf1-x441.google.com [IPv6:2607:f8b0:4864:20::441]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id CE453211E7444 for ; Tue, 2 Apr 2019 11:40:57 -0700 (PDT) Received: by mail-pf1-x441.google.com with SMTP id i17so6812354pfo.6 for ; Tue, 02 Apr 2019 11:40:57 -0700 (PDT) Date: Tue, 2 Apr 2019 14:40:54 -0400 From: Joel Fernandes Subject: Re: [PATCH RFC tip/core/rcu 0/4] Forbid static SRCU use in modules Message-ID: <20190402184054.GA18150@google.com> References: <20190402142816.GA13084@linux.ibm.com> <886051277.1395.1554218080591.JavaMail.zimbra@efficios.com> <20190402152334.GC4102@linux.ibm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190402152334.GC4102@linux.ibm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: "Paul E. McKenney" Cc: David Howells , amd-gfx@lists.freedesktop.org, Thomas Gleixner , linux-nvdimm@lists.01.org, Peter Zijlstra , fweisbec , dri-devel@lists.freedesktop.org, Lai Jiangshan , linux-kernel , rostedt , Josh Triplett , rcu@vger.kernel.org, Eric Dumazet , Mathieu Desnoyers , Oleg Nesterov , dipankar , Andrew Morton , Ingo Molnar List-ID: On Tue, Apr 02, 2019 at 08:23:34AM -0700, Paul E. McKenney wrote: > On Tue, Apr 02, 2019 at 11:14:40AM -0400, Mathieu Desnoyers wrote: > > ----- On Apr 2, 2019, at 10:28 AM, paulmck paulmck@linux.ibm.com wrote: > > > > > Hello! > > > > > > This series prohibits use of DEFINE_SRCU() and DEFINE_STATIC_SRCU() > > > by loadable modules. The reason for this prohibition is the fact > > > that using these two macros within modules requires that the size of > > > the reserved region be increased, which is not something we want to > > > be doing all that often. Instead, loadable modules should define an > > > srcu_struct and invoke init_srcu_struct() from their module_init function > > > and cleanup_srcu_struct() from their module_exit function. Note that > > > modules using call_srcu() will also need to invoke srcu_barrier() from > > > their module_exit function. > > > > This arbitrary API limitation seems weird. > > > > Isn't there a way to allow modules to use DEFINE_SRCU and DEFINE_STATIC_SRCU > > while implementing them with dynamic allocation under the hood ? > > Although call_srcu() already has initialization hooks, some would > also be required in srcu_read_lock(), and I am concerned about adding > memory allocation at that point, especially given the possibility > of memory-allocation failure. And the possibility that the first > srcu_read_lock() happens in an interrupt handler or similar. > > Or am I missing a trick here? Hi Paul, Which 'reserved region' are you referring to? Isn't this region also used for non-module cases in which case the same problem applies to non-modules? thanks! - Joel _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm