Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932362Ab2JNOoA (ORCPT ); Sun, 14 Oct 2012 10:44:00 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:46679 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932301Ab2JNOnx (ORCPT ); Sun, 14 Oct 2012 10:43:53 -0400 Message-Id: <20121014143540.939763440@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Sun, 14 Oct 2012 15:36:25 +0100 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Dan Williams , Jack Wang , John Drescher , James Bottomley Subject: [ 052/147] [SCSI] scsi_remove_target: fix softlockup regression on hot remove In-Reply-To: <20121014143533.742627615@decadent.org.uk> X-SA-Exim-Connect-IP: 77.75.106.1 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3151 Lines: 96 3.2-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: Ben Hutchings --- drivers/scsi/scsi_sysfs.c | 30 ++++++++++++++---------------- 1 file changed, 14 insertions(+), 16 deletions(-) diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c index 093d4f6..ce5224c 100644 --- a/drivers/scsi/scsi_sysfs.c +++ b/drivers/scsi/scsi_sysfs.c @@ -1031,33 +1031,31 @@ static void __scsi_remove_target(struct scsi_target *starget) 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); -- 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/