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=-2.1 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, 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 61265C433F5 for ; Thu, 30 Aug 2018 14:29:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 10179205C9 for ; Thu, 30 Aug 2018 14:29:28 +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="jlFq0QJ4" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 10179205C9 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729240AbeH3Sbv (ORCPT ); Thu, 30 Aug 2018 14:31:51 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:32972 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729035AbeH3Sbu (ORCPT ); Thu, 30 Aug 2018 14:31:50 -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=V0aFxzFNjJIetc8WMsMUaz+Ek+jNFeACrTW7ULxgVHs=; b=jlFq0QJ4Y3ehNv/qHoGUoIRZp J9mfDaZd+CucksTBO1RHYIqckIJ8tRNWneEBe9WoSPaiSxc4MdTqsd4f0VnhEbLB4Mo57yJsCK7Bg 8EgzxG5J4Cc6D1/E47kg9ZeI00w8IMOrX4Y6BtgOlFcTaOIFau6eZ3pANzU46EUb2w8GixcQMPETe 8C45jiZnmjwROIVR2Ty6RZfbUme8FPX1B3+p7GHJXdVZE8niDi8FuRM3OkpkkdMRcuVozeKMY00OW Jcyu/YyPJEdH6lG0CHNyuaIoVh5LXOMIDOFKOkWH99/XoCEzK3USw8L56eim5yuzw4aghaTegHLkn s1jo1erBQ==; 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 1fvNwn-0001Pz-T4; Thu, 30 Aug 2018 14:29:22 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 42A242024D73F; Thu, 30 Aug 2018 16:29:20 +0200 (CEST) Date: Thu, 30 Aug 2018 16:29:20 +0200 From: Peter Zijlstra To: Will Deacon Cc: Eugeniy Paltsev , "mingo@kernel.org" , "linux-kernel@vger.kernel.org" , "Alexey.Brodkin@synopsys.com" , "Vineet.Gupta1@synopsys.com" , "tglx@linutronix.de" , "linux-snps-arc@lists.infradead.org" , "yamada.masahiro@socionext.com" , "linux-arm-kernel@lists.infradead.org" , "linux-arch@vger.kernel.org" Subject: Re: Patch "asm-generic/bitops/lock.h: Rewrite using atomic_fetch_" causes kernel crash Message-ID: <20180830142920.GO24082@hirez.programming.kicks-ass.net> References: <1535567633.4465.23.camel@synopsys.com> <20180830094411.GX24124@hirez.programming.kicks-ass.net> <20180830095148.GB5942@arm.com> <1535629996.4465.44.camel@synopsys.com> <20180830141713.GN24082@hirez.programming.kicks-ass.net> <20180830142354.GB13005@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180830142354.GB13005@arm.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 30, 2018 at 03:23:55PM +0100, Will Deacon wrote: > Yes, that would be worth trying. However, I also just noticed that the > fetch-ops (which are now used to implement test_and_set_bit_lock()) seem > to be missing the backwards branch in the LL/SC case. Yet another diff > below. > > Will > > --->8 > > diff --git a/arch/arc/include/asm/atomic.h b/arch/arc/include/asm/atomic.h > index 4e0072730241..f06c5ed672b3 100644 > --- a/arch/arc/include/asm/atomic.h > +++ b/arch/arc/include/asm/atomic.h > @@ -84,7 +84,7 @@ static inline int atomic_fetch_##op(int i, atomic_t *v) \ > "1: llock %[orig], [%[ctr]] \n" \ > " " #asm_op " %[val], %[orig], %[i] \n" \ > " scond %[val], [%[ctr]] \n" \ > - " \n" \ > + " bnz 1b \n" \ > : [val] "=&r" (val), \ > [orig] "=&r" (orig) \ > : [ctr] "r" (&v->counter), \ ACK!! sorry about that, no idea how I messed that up. Also, once it all works, they should look at switching to _relaxed atomics for LL/SC.