Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751590AbaJIUlR (ORCPT ); Thu, 9 Oct 2014 16:41:17 -0400 Received: from mail-la0-f51.google.com ([209.85.215.51]:41619 "EHLO mail-la0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750815AbaJIUlO (ORCPT ); Thu, 9 Oct 2014 16:41:14 -0400 Date: Thu, 9 Oct 2014 22:41:01 +0200 From: Rabin Vincent To: Felipe Balbi Cc: Johannes Weiner , Andrew Morton , Linus Torvalds , Sasha Levin , "Paul E. McKenney" , Linux USB Mailing List , Alan Stern , josh@joshtriplett.org, Linux Kernel Mailing List , Tony Lindgren , Linux OMAP Mailing List , Linux ARM Kernel Mailing List , Rik van Riel Subject: Re: RCU bug with v3.17-rc3 ? Message-ID: <20141009204101.GA25955@debian> References: <20140904184021.GA13421@saruman.home> <20140904191642.GJ5001@linux.vnet.ibm.com> <20140904192535.GJ13421@saruman.home> <20140904200403.GL13421@saruman.home> <20140905213216.GD5001@linux.vnet.ibm.com> <20141008171322.GH22688@saruman> <20141008175707.GI22688@saruman> <20141008212938.GP22688@saruman> <20141009160138.GA2396@cmpxchg.org> <20141009162656.GE16002@saruman> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141009162656.GE16002@saruman> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 09, 2014 at 11:26:56AM -0500, Felipe Balbi wrote: > alright, it's pretty deterministic however. Always on the same test, no > matter which USB controller, no matter if backing store is RAM or MMC. > > Those two undefined instructions on the disassembly caught my attention, > perhaps I'm facing a GCC bug ? The undefined instructions are just ARM's BUG() implementation. But did you see the question I asked you yesterday in your other thread? http://www.spinics.net/lists/arm-kernel/msg368634.html Here it is again: What GCC version are you using? 4.8.1 and 4.8.2 are known to miscompile the ARM kernel and these find_get_entry() crashes with 0xffffffff involved smell a lot like the earlier reports from kernels build with those compilers: https://lkml.org/lkml/2014/6/25/456 https://lkml.org/lkml/2014/6/30/375 https://lkml.org/lkml/2014/6/30/660 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58854 https://lkml.org/lkml/2014/5/9/330 Also, I didn't see any public email making a definitive link between GCC PR 58854 that Nathan pointed out in https://lkml.org/lkml/2014/6/30/660 and the earlier find_get_entry() crashes, but I just built GCC 4.8.1 and an ARM kernel with that, and the GCC bug is clearly seen in radix_tree_lookup_slot() which returns the pointer which find_get_entry() is dereferencing: : e1a0c00d mov ip, sp e92dd800 push {fp, ip, lr, pc} e24cb004 sub fp, ip, #4 e24dd008 sub sp, sp, #8 e3a02000 mov r2, #0 e24b3010 sub r3, fp, #16 ebffffc5 bl c0176ab8 <__radix_tree_lookup> e24bd00c sub sp, fp, #12 <--- sp moved up e3500000 cmp r0, #0 151b0010 ldrne r0, [fp, #-16] <--- load from under sp e89da800 ldm sp, {fp, sp, pc} Please check your compiler to make sure it's not the same problem. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/