From 2544cce12c7bd18e880b09c21b1a2d944a3423eb Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Mon, 19 Oct 2015 16:35:46 +0200 Subject: [PATCH] scsi: restart list search after unlock in scsi_remove_target commit 40998193560dab6c3ce8d25f4fa58a23e252ef38 upstream. When dropping a lock while iterating a list we must restart the search as other threads could have manipulated the list under us. Without this we can get stuck in an endless loop. This bug was introduced by commit bc3f02a795d3b4faa99d37390174be2a75d091bd Author: Dan Williams Date: Tue Aug 28 22:12:10 2012 -0700 [SCSI] scsi_remove_target: fix softlockup regression on hot remove Which was itself trying to fix a reported soft lockup issue http://thread.gmane.org/gmane.linux.kernel/1348679 However, we believe even with this revert of the original patch, the soft lockup problem has been fixed by commit f2495e228fce9f9cec84367547813cbb0d6db15a Author: James Bottomley Date: Tue Jan 21 07:01:41 2014 -0800 [SCSI] dual scan thread bug fix Thanks go to Dan Williams for tracking all this prior history down. Reported-by: Johannes Thumshirn Signed-off-by: Christoph Hellwig Tested-by: Johannes Thumshirn Reviewed-by: Johannes Thumshirn Fixes: bc3f02a795d3b4faa99d37390174be2a75d091bd Signed-off-by: James Bottomley Signed-off-by: Greg Kroah-Hartman --- drivers/scsi/scsi_sysfs.c | 16 ++++------------ 1 file changed, 4 insertions(+), 12 deletions(-) diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c index 9e2dd478dd15..91c39552c2cd 100644 --- a/drivers/scsi/scsi_sysfs.c +++ b/drivers/scsi/scsi_sysfs.c @@ -1030,31 +1030,23 @@ 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, *last = NULL; + struct scsi_target *starget; unsigned long flags; - /* remove targets being careful to lookup next entry before - * deleting the last - */ +restart: 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) { - /* assuming new targets arrive at the end */ kref_get(&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); + scsi_target_reap(starget); + goto restart; } } spin_unlock_irqrestore(shost->host_lock, flags); - - if (last) - scsi_target_reap(last); } EXPORT_SYMBOL(scsi_remove_target); -- 2.20.1