From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933601Ab2JDVTj (ORCPT ); Thu, 4 Oct 2012 17:19:39 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:40785 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933584Ab2JDVTb (ORCPT ); Thu, 4 Oct 2012 17:19:31 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , alan@lxorguk.ukuu.org.uk, Jack Wang , John Drescher , Dan Williams , James Bottomley Subject: [ 55/56] SCSI: scsi_remove_target: fix softlockup regression on hot remove Date: Thu, 4 Oct 2012 14:16:16 -0700 Message-Id: <20121004211158.373013789@linuxfoundation.org> X-Mailer: git-send-email 1.7.12.2.421.g261b511 In-Reply-To: <20121004211152.101901246@linuxfoundation.org> References: <20121004211152.101901246@linuxfoundation.org> User-Agent: quilt/0.60-2.1.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Dan Williams commit bc3f02a795d3b4faa99d37390174be2a75d091bd upstream. John reports: BUG: soft lockup - CPU#2 stuck for 23s! [kworker/u:8:2202] [..] Call Trace: [] scsi_remove_target+0xda/0x1f0 [] sas_rphy_remove+0x55/0x60 [] sas_rphy_delete+0x11/0x20 [] sas_port_delete+0x25/0x160 [] mptsas_del_end_device+0x183/0x270 ...introduced by commit 3b661a9 "[SCSI] fix hot unplug vs async scan race". Don't restart lookup of more stargets in the multi-target case, just arrange to traverse the list once, on the assumption that new targets are always added at the end. There is no guarantee that the target will change state in scsi_target_reap() so we can end up spinning if we restart. Acked-by: Jack Wang LKML-Reference: Reported-by: John Drescher Tested-by: John Drescher Signed-off-by: Dan Williams Signed-off-by: James Bottomley Signed-off-by: Greg Kroah-Hartman --- drivers/scsi/scsi_sysfs.c | 30 ++++++++++++++---------------- 1 file changed, 14 insertions(+), 16 deletions(-) --- a/drivers/scsi/scsi_sysfs.c +++ b/drivers/scsi/scsi_sysfs.c @@ -1031,33 +1031,31 @@ static void __scsi_remove_target(struct void scsi_remove_target(struct device *dev) { struct Scsi_Host *shost = dev_to_shost(dev->parent); - struct scsi_target *starget, *found; + struct scsi_target *starget, *last = NULL; unsigned long flags; - restart: - found = NULL; + /* remove targets being careful to lookup next entry before + * deleting the last + */ spin_lock_irqsave(shost->host_lock, flags); list_for_each_entry(starget, &shost->__targets, siblings) { if (starget->state == STARGET_DEL) continue; if (starget->dev.parent == dev || &starget->dev == dev) { - found = starget; - found->reap_ref++; - break; + /* assuming new targets arrive at the end */ + starget->reap_ref++; + spin_unlock_irqrestore(shost->host_lock, flags); + if (last) + scsi_target_reap(last); + last = starget; + __scsi_remove_target(starget); + spin_lock_irqsave(shost->host_lock, flags); } } spin_unlock_irqrestore(shost->host_lock, flags); - if (found) { - __scsi_remove_target(found); - scsi_target_reap(found); - /* in the case where @dev has multiple starget children, - * continue removing. - * - * FIXME: does such a case exist? - */ - goto restart; - } + if (last) + scsi_target_reap(last); } EXPORT_SYMBOL(scsi_remove_target);