From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5B891C433E6 for ; Fri, 28 Aug 2020 08:58:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 387232071B for ; Fri, 28 Aug 2020 08:58:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="bhk52EPR" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728731AbgH1I6A (ORCPT ); Fri, 28 Aug 2020 04:58:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60746 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728501AbgH1I56 (ORCPT ); Fri, 28 Aug 2020 04:57:58 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C3634C061264 for ; Fri, 28 Aug 2020 01:57:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=jh+K2Qasy0dQnK1uvT/EeMP7bA1n+DIGMgJY0Q/GdaY=; b=bhk52EPRlRQtj4hjNqp2dQAUpT p3wGac0Y0OZ6DzlywXgXj41nddyy8whMv5LL9btkjpdv3axErC6Ln0H0WLitbTwDOJZw6QsMTZdeI GsH0FhxdW8rby/mg6NsiufBuiBVahRG14moyK+Zn3NNForrenMJPrm2D6Io6pWbqSzaJtN7qjIzmE nVE6hfqk7je4xJhdqgN1VfePSI6Mu283M6DIz6hFcgFmuBm54NaIMIbqdLZhGaHd2LEwxIAgAECrw Pv9i2Cg17VqlYPM2x71q7ifb/r2KkjjCpdMPaQm9u5OEhHdOuIh3XH4AHDu6e8nSJNDVvBAHLT5hE YC4c+lGQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kBaCl-0005ds-D5; Fri, 28 Aug 2020 08:57:51 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id D96733003E5; Fri, 28 Aug 2020 10:57:50 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id C5F242C56E648; Fri, 28 Aug 2020 10:57:50 +0200 (CEST) Date: Fri, 28 Aug 2020 10:57:50 +0200 From: peterz@infradead.org To: "Ahmed S. Darwish" Cc: Ingo Molnar , Will Deacon , Thomas Gleixner , "Sebastian A. Siewior" , "Paul E. McKenney" , Steven Rostedt , LKML Subject: Re: [PATCH v1 4/5] seqlock: seqcount_LOCKTYPE_t: Introduce PREEMPT_RT support Message-ID: <20200828085750.GR1362448@hirez.programming.kicks-ass.net> References: <20200519214547.352050-1-a.darwish@linutronix.de> <20200828010710.5407-1-a.darwish@linutronix.de> <20200828010710.5407-5-a.darwish@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200828010710.5407-5-a.darwish@linutronix.de> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 28, 2020 at 03:07:09AM +0200, Ahmed S. Darwish wrote: > +/* > + * Automatically disable preemption for seqcount_LOCKTYPE_t writers, if the > + * associated lock does not implicitly disable preemption. > + * > + * Don't do it for PREEMPT_RT. Check __SEQ_LOCK(). > + */ > +#define __seq_enforce_preemption_protection(s) \ > + (!IS_ENABLED(CONFIG_PREEMPT_RT) && __seqcount_lock_preemptible(s)) Hurph, so basically you want to make __seqcount_lock_preemptible() return true PREEMPT_RT ? Should we then not muck about with the propery instead of this? ISTR I had something like the below, would that not be the same but much clearer ? diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h index 300cbf312546..3b5ad026ddfb 100644 --- a/include/linux/seqlock.h +++ b/include/linux/seqlock.h @@ -211,11 +211,13 @@ static inline void __seqcount_assert(seqcount_t *s) lockdep_assert_preemption_disabled(); } -SEQCOUNT_LOCKTYPE(raw_spinlock_t, raw_spinlock, false, s->lock) -SEQCOUNT_LOCKTYPE(spinlock_t, spinlock, false, s->lock) -SEQCOUNT_LOCKTYPE(rwlock_t, rwlock, false, s->lock) -SEQCOUNT_LOCKTYPE(struct mutex, mutex, true, s->lock) -SEQCOUNT_LOCKTYPE(struct ww_mutex, ww_mutex, true, &s->lock->base) +#define __PREEMPT_RT IS_BUILTIN(CONFIG_PREEMPT_RT) + +SEQCOUNT_LOCKTYPE(raw_spinlock_t, raw_spinlock, false, s->lock) +SEQCOUNT_LOCKTYPE(spinlock_t, spinlock, __PREEMPT_RT, s->lock) +SEQCOUNT_LOCKTYPE(rwlock_t, rwlock, __PREEMPT_RT, s->lock) +SEQCOUNT_LOCKTYPE(struct mutex, mutex, true, s->lock) +SEQCOUNT_LOCKTYPE(struct ww_mutex, ww_mutex, true, &s->lock->base) /* * SEQCNT_LOCKNAME_ZERO - static initializer for seqcount_LOCKNAME_t