From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754253Ab0GNRCJ (ORCPT ); Wed, 14 Jul 2010 13:02:09 -0400 Received: from mail.candelatech.com ([208.74.158.172]:49786 "EHLO ns3.lanforge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753612Ab0GNRCI (ORCPT ); Wed, 14 Jul 2010 13:02:08 -0400 From: Ben Greear To: linux-kernel@vger.kernel.org Cc: Ben Greear Subject: [pci] pci/mrst: Detect loops when reading fixed BAR cap. Date: Wed, 14 Jul 2010 10:02:03 -0700 Message-Id: <1279126923-27926-1-git-send-email-greearb@candelatech.com> X-Mailer: git-send-email 1.6.2.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The mrst logic introduced in 2.6.33-rc8 in commit a712ffbc199849364c46e9112b93b66de08e2c26 causes boot to hang on at least this platform: Intel E5405 CPU System Information Manufacturer: Supermicro Product Name: X7DBU The cause of the hang is that pci_cap points to itself as the next capability, putting the fixed_bar_cap into an endless loop. This patch detects the loop, prints a warning, and continues on with useful work. This strategy was suggested by Robert Hancock This should be a candidate for 2.6.34.y as well. Signed-off-by: Ben Greear --- :100644 100644 1cdc02c... 9535ba9... M arch/x86/pci/mrst.c arch/x86/pci/mrst.c | 11 +++++++++++ 1 files changed, 11 insertions(+), 0 deletions(-) diff --git a/arch/x86/pci/mrst.c b/arch/x86/pci/mrst.c index 1cdc02c..9535ba9 100644 --- a/arch/x86/pci/mrst.c +++ b/arch/x86/pci/mrst.c @@ -76,6 +76,17 @@ static int fixed_bar_cap(struct pci_bus *bus, unsigned int devfn) return pos; } + if ((pcie_cap >> 20) == 0) + break; + + if ((pcie_cap >> 20) <= pos) { + printk(KERN_WARNING "WARNING: mrst: detected loop" + " when searching for fixed BAR cap, previous" + " position: 0x%x new position: 0x%x" + " bus-number: %i devfn: %i\n", + pos, pcie_cap >> 20, bus->number, devfn); + break; + } pos = pcie_cap >> 20; } -- 1.6.2.5