From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966621AbcKOKEI (ORCPT ); Tue, 15 Nov 2016 05:04:08 -0500 Received: from mail-wm0-f65.google.com ([74.125.82.65]:33293 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S941376AbcKOKED (ORCPT ); Tue, 15 Nov 2016 05:04:03 -0500 Date: Tue, 15 Nov 2016 11:03:59 +0100 From: Ingo Molnar To: Peter Zijlstra Cc: gregkh@linuxfoundation.org, keescook@chromium.org, will.deacon@arm.com, elena.reshetova@intel.com, arnd@arndb.de, tglx@linutronix.de, hpa@zytor.com, dave@progbits.org, Linus Torvalds , linux-kernel@vger.kernel.org Subject: Re: [RFC][PATCH 7/7] kref: Implement using refcount_t Message-ID: <20161115100359.GA7757@gmail.com> References: <20161114173946.501528675@infradead.org> <20161114174446.832175072@infradead.org> <20161115084009.GB15734@gmail.com> <20161115094744.GG3142@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161115094744.GG3142@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Peter Zijlstra wrote: > On Tue, Nov 15, 2016 at 09:40:09AM +0100, Ingo Molnar wrote: > > > > * Peter Zijlstra wrote: > > > > > Provide refcount_t, an atomic_t like primitive built just for > > > refcounting. > > > > > > It provides overflow and underflow checks as well as saturation > > > semantics such that when it overflows, we'll never attempt to free it > > > again, ever. > > > > > > Signed-off-by: Peter Zijlstra (Intel) > > > --- > > > include/linux/kref.h | 29 ++---- > > > include/linux/refcount.h | 221 +++++++++++++++++++++++++++++++++++++++++++++++ > > > 2 files changed, 232 insertions(+), 18 deletions(-) > > > > I'd suggest splitting this patch into two parts: first patch introduces the > > refcount.h facility, second patch changes over struct kref to the new facility. > > You're right, I was just really glad I got it to compile and didn't want > to prod more at it. > > Should I also make a CONFIG knob that implements refcount_t with the > 'normal' atomic_t primitives? I'd suggest doing the saturation/safe-wrap semantics only for now (i.e. the current patch, split into two perhaps), and reconsider if there's any complaints? > And possibly another knob to toggle the BUG()s into WARN()s. With the > full saturation semantics WARN() is a lot safer and will not corrupt > kernel state as much. I'd suggest changing it to a WARN() straight away, no extra knobs. Thanks, Ingo