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 6C12AC433F5 for ; Thu, 30 Aug 2018 14:17:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 25FB32073D for ; Thu, 30 Aug 2018 14:17:23 +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="AyyhI0TM" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 25FB32073D 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 S1729242AbeH3STm (ORCPT ); Thu, 30 Aug 2018 14:19:42 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:51014 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729080AbeH3STl (ORCPT ); Thu, 30 Aug 2018 14:19:41 -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=nQFQWuWAaE2h2gwOIdyZjpCcGVFc/ZfL+60lnpyWtxc=; b=AyyhI0TMsuaJo1NwckOLjbz9g uNHjYzK3QYLlaqfWAdt1jd71A6UVvqtNklqKQTcWP4Pwfo10a7OgfbJ1ISChNn45mpblqaQQ5ZU5m AxxPx5P5UQoAG5KN+adLJgzCjuhwXCxgW9L97LfVr2rlYGZX7uBDVby1FlYzFSrOnW5vq/7hyw1TD 6MWzop93ZElwVMIMgOBhjS7hUxl6zCZh6qYgGoqrpMHZPlPG5yZlw09unIhJqSK37O0Vwa+ouvSCa ncCY2LmRj9x26psRqj7TYjMt4fYYkTzx6eRXdcdf2yTOShEPTsBRVOHDLjPiJ96Tb/j6SryZ3mMy2 C+95PrHlw==; 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 1fvNl5-0004eV-3v; Thu, 30 Aug 2018 14:17:15 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 9D80C2024D444; Thu, 30 Aug 2018 16:17:13 +0200 (CEST) Date: Thu, 30 Aug 2018 16:17:13 +0200 From: Peter Zijlstra To: Eugeniy Paltsev Cc: "will.deacon@arm.com" , "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: <20180830141713.GN24082@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1535629996.4465.44.camel@synopsys.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 11:53:17AM +0000, Eugeniy Paltsev wrote: > I can see crashes with LLSC enabled in both SMP running on 4 cores > and SMP running on 1 core. So you're running on LL/SC enabled hardware; that would make Will's patch irrelevant (although still a good idea for the hardware that does care about that spinlocked atomic crud). Does something like the below cure things? That would confirm the suggestion that the change to __clear_bit_unlock() is the curprit. If that doesn't cure things, then we've been looking in entirely the wrong place. --- diff --git a/include/asm-generic/bitops/lock.h b/include/asm-generic/bitops/lock.h index 3ae021368f48..79c6978152f8 100644 --- a/include/asm-generic/bitops/lock.h +++ b/include/asm-generic/bitops/lock.h @@ -57,12 +57,7 @@ static inline void clear_bit_unlock(unsigned int nr, volatile unsigned long *p) static inline void __clear_bit_unlock(unsigned int nr, volatile unsigned long *p) { - unsigned long old; - - p += BIT_WORD(nr); - old = READ_ONCE(*p); - old &= ~BIT_MASK(nr); - atomic_long_set_release((atomic_long_t *)p, old); + clear_bit_unlock(nr, p); } /**