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=-5.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, 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 50BABC072B5 for ; Fri, 24 May 2019 10:38:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2415B217D7 for ; Fri, 24 May 2019 10:38:23 +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="ee0aSNpW" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390579AbfEXKiW (ORCPT ); Fri, 24 May 2019 06:38:22 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:42420 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390583AbfEXKiW (ORCPT ); Fri, 24 May 2019 06:38:22 -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=1SIR/nalPssf/0C1EVzh7EOnaBoQ17v7Xe1OGlM5rzQ=; b=ee0aSNpWwygM7bJYH/G/7m8DJ furwOdTstRcsrNpmN6Fq7aPPCYd1qriYL+0cGkWIpIHLqhGZ37wZt9y5WBYxirfSgiawpKxOngZRa OlXZxOVYDAMUBWCCN7+NOR4XYxA4iEWLObX/+hB2Osox4bvPTH+Mf3vFeTrTSGxRwCY2f3IOy4NLl AByn3HSQKiBeHrmeS3w1Fc1nTXquwTd9QJHWETl+2H0XVaAI8Pl0m4bRdoOYU7qBilW2NO7xAIn4I fk6P9Sa0/wnKYE1Hv3bn4kHNE9bYrYeBJD9k66Qq5HlyETDzDRcXbG3u5CnH9oS8zaqyo9BP8JbCN YGudmZBJQ==; 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 1hU7Zu-0006du-ET; Fri, 24 May 2019 10:37:34 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 0835320281C32; Fri, 24 May 2019 12:37:32 +0200 (CEST) Date: Fri, 24 May 2019 12:37:31 +0200 From: Peter Zijlstra To: Mark Rutland Cc: Andrea Parri , linux-kernel@vger.kernel.org, will.deacon@arm.com, aou@eecs.berkeley.edu, arnd@arndb.de, bp@alien8.de, catalin.marinas@arm.com, davem@davemloft.net, fenghua.yu@intel.com, heiko.carstens@de.ibm.com, herbert@gondor.apana.org.au, ink@jurassic.park.msu.ru, jhogan@kernel.org, linux@armlinux.org.uk, mattst88@gmail.com, mingo@kernel.org, mpe@ellerman.id.au, palmer@sifive.com, paul.burton@mips.com, paulus@samba.org, ralf@linux-mips.org, rth@twiddle.net, stable@vger.kernel.org, tglx@linutronix.de, tony.luck@intel.com, vgupta@synopsys.com, gregkh@linuxfoundation.org, jhansen@vmware.com, vdasa@vmware.com, aditr@vmware.com, Steven Rostedt Subject: Re: [PATCH 00/18] locking/atomic: atomic64 type cleanup Message-ID: <20190524103731.GN2606@hirez.programming.kicks-ass.net> References: <20190522132250.26499-1-mark.rutland@arm.com> <20190523083013.GA4616@andrea> <20190523101926.GA3370@lakrids.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190523101926.GA3370@lakrids.cambridge.arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Thu, May 23, 2019 at 11:19:26AM +0100, Mark Rutland wrote: > [mark@lakrids:~/src/linux]% git grep '\(return\|=\)\s\+atomic\(64\)\?_set' > include/linux/vmw_vmci_defs.h: return atomic_set((atomic_t *)var, (u32)new_val); > include/linux/vmw_vmci_defs.h: return atomic64_set(var, new_val); > Oh boy, what a load of crap you just did find. How about something like the below? I've not read how that buffer is used, but the below preserves all broken without using atomic*_t. --- diff --git a/include/linux/vmw_vmci_defs.h b/include/linux/vmw_vmci_defs.h index 0c06178e4985..8ee472118f54 100644 --- a/include/linux/vmw_vmci_defs.h +++ b/include/linux/vmw_vmci_defs.h @@ -438,8 +438,8 @@ enum { struct vmci_queue_header { /* All fields are 64bit and aligned. */ struct vmci_handle handle; /* Identifier. */ - atomic64_t producer_tail; /* Offset in this queue. */ - atomic64_t consumer_head; /* Offset in peer queue. */ + u64 producer_tail; /* Offset in this queue. */ + u64 consumer_head; /* Offset in peer queue. */ }; /* @@ -740,13 +740,9 @@ static inline void *vmci_event_data_payload(struct vmci_event_data *ev_data) * prefix will be used, so correctness isn't an issue, but using a * 64bit operation still adds unnecessary overhead. */ -static inline u64 vmci_q_read_pointer(atomic64_t *var) +static inline u64 vmci_q_read_pointer(u64 *var) { -#if defined(CONFIG_X86_32) - return atomic_read((atomic_t *)var); -#else - return atomic64_read(var); -#endif + return READ_ONCE(*(unsigned long *)var); } /* @@ -755,23 +751,17 @@ static inline u64 vmci_q_read_pointer(atomic64_t *var) * never exceeds a 32bit value in this case. On 32bit SMP, using a * locked cmpxchg8b adds unnecessary overhead. */ -static inline void vmci_q_set_pointer(atomic64_t *var, - u64 new_val) +static inline void vmci_q_set_pointer(u64 *var, u64 new_val) { -#if defined(CONFIG_X86_32) - return atomic_set((atomic_t *)var, (u32)new_val); -#else - return atomic64_set(var, new_val); -#endif + /* XXX buggered on big-endian */ + WRITE_ONCE(*(unsigned long *)var, (unsigned long)new_val); } /* * Helper to add a given offset to a head or tail pointer. Wraps the * value of the pointer around the max size of the queue. */ -static inline void vmci_qp_add_pointer(atomic64_t *var, - size_t add, - u64 size) +static inline void vmci_qp_add_pointer(u64 *var, size_t add, u64 size) { u64 new_val = vmci_q_read_pointer(var); @@ -848,8 +838,8 @@ static inline void vmci_q_header_init(struct vmci_queue_header *q_header, const struct vmci_handle handle) { q_header->handle = handle; - atomic64_set(&q_header->producer_tail, 0); - atomic64_set(&q_header->consumer_head, 0); + q_header->producer_tail = 0; + q_header->consumer_head = 0; } /*