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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 44932C10F13 for ; Tue, 16 Apr 2019 14:42:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1089820693 for ; Tue, 16 Apr 2019 14:42:41 +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="qK7S0mj8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729670AbfDPOmj (ORCPT ); Tue, 16 Apr 2019 10:42:39 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:46096 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726837AbfDPOmj (ORCPT ); Tue, 16 Apr 2019 10:42:39 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=SueId32iFbRwQuPfy1oY9eCQkdDDSAd9MpnI8G4atNI=; b=qK7S0mj8gni6on4tipdmSvSeP J09LqXn5SNRzXcDbjZnuHVgMH2Gg8BVCh2gqf4ZudICsQJi4rOgOlj2O9TwjpHOVsrAIGVQpsZ8US WyuY3M4hR3jgSuj6gRIeZ9SwML0524el7wGJikh0+h2c+O5gxCB29pvHLQlj3aRTEVNS8tIjXsDFU 6Ph+wrDJnW2Djc71FyZpBkauM7xfG61tRFxkU3eODjIOG0T3Rakkpfd7wg6UykW+JcAIygCkwvMRX MczdxPl4k5qPxt6eHwb10PrRXP/Be8VmV2l/EimKmGKmhYSfKl1hjM9kDJixJlQhZtHOVLeItv9AK jziDaV9Zw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1hGPI9-0007Mh-EX; Tue, 16 Apr 2019 14:42:33 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 5CE6829AC163A; Tue, 16 Apr 2019 16:42:31 +0200 (CEST) Date: Tue, 16 Apr 2019 16:42:31 +0200 From: Peter Zijlstra To: Waiman Long Cc: Ingo Molnar , Will Deacon , Thomas Gleixner , linux-kernel@vger.kernel.org, x86@kernel.org, Davidlohr Bueso , Linus Torvalds , Tim Chen , huang ying Subject: Re: [PATCH v4 04/16] locking/rwsem: Implement a new locking scheme Message-ID: <20190416144231.GQ14281@hirez.programming.kicks-ass.net> References: <20190413172259.2740-1-longman@redhat.com> <20190413172259.2740-5-longman@redhat.com> <20190416132218.GJ12232@hirez.programming.kicks-ass.net> <20190416141820.GO4038@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190416141820.GO4038@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 16, 2019 at 04:18:20PM +0200, Peter Zijlstra wrote: > On Tue, Apr 16, 2019 at 09:32:38AM -0400, Waiman Long wrote: > > On 04/16/2019 09:22 AM, Peter Zijlstra wrote: > > > On Sat, Apr 13, 2019 at 01:22:47PM -0400, Waiman Long wrote: > > >> +#define RWSEM_COUNT_LOCKED(c) ((c) & RWSEM_LOCK_MASK) > > > The above doesn't seem to make it more readable or shorter. > > > > Fair enough. I can remove that macro. > > I did the same for the HANDOFF patch but seem to have misplaced the > delta and have already refreshed the patch. Had to redo it, so here goes: --- --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -102,9 +102,6 @@ #define RWSEM_READ_FAILED_MASK (RWSEM_WRITER_MASK|RWSEM_FLAG_WAITERS|\ RWSEM_FLAG_HANDOFF) -#define RWSEM_COUNT_HANDOFF(c) ((c) & RWSEM_FLAG_HANDOFF) -#define RWSEM_COUNT_LOCKED_OR_HANDOFF(c) \ - ((c) & (RWSEM_LOCK_MASK|RWSEM_FLAG_HANDOFF)) /* * All writes to owner are protected by WRITE_ONCE() to make sure that * store tearing can't happen as optimistic spinners may read and use @@ -365,7 +362,7 @@ static void __rwsem_mark_wake(struct rw_ /* * Clear the handoff flag */ - if (woken && RWSEM_COUNT_HANDOFF(atomic_long_read(&sem->count))) + if (woken && (atomic_long_read(&sem->count) & RWSEM_FLAG_HANDOFF)) adjustment -= RWSEM_FLAG_HANDOFF; if (adjustment) @@ -387,7 +384,7 @@ static inline bool rwsem_try_write_lock( retry: if (count & RWSEM_LOCK_MASM)) { - if (RWSEM_COUNT_HANDOFF(count) || (wstate != WRITER_HANDOFF)) + if ((count & RWSEM_FLAG_HANDOFF) || (wstate != WRITER_HANDOFF)) return false; /* * The lock may become free just before setting handoff bit. @@ -398,7 +395,7 @@ static inline bool rwsem_try_write_lock( goto retry; } - if ((wstate == WRITER_NOT_FIRST) && RWSEM_COUNT_HANDOFF(count)) + if ((wstate == WRITER_NOT_FIRST) && (count & RWSEM_FLAG_HANDOFF)) return false; new = (count & ~RWSEM_FLAG_HANDOFF) + RWSEM_WRITER_LOCKED - @@ -409,7 +406,7 @@ static inline bool rwsem_try_write_lock( return true; } - if (unlikely((wstate == WRITER_HANDOFF) && !RWSEM_COUNT_HANDOFF(count))) + if (unlikely((wstate == WRITER_HANDOFF) && !(count & RWSEM_FLAG_HANDOFF))) goto retry; return false; @@ -704,7 +701,7 @@ __rwsem_down_write_failed_common(struct rwsem_waiter_is_first(sem, &waiter)) wstate = WRITER_FIRST; - if (!RWSEM_COUNT_LOCKED(count)) + if (!(count & RWSEM_LOCK_MASK)) break; /*