From: Hans-Joachim Picht <hpicht@redhat.com>
Date: Mon, 10 Dec 2007 14:03:30 +0100
Subject: [s390] zfcp: Deadlock when adding invalid LUN
Message-id: 20071210130330.GB29540@redhat.com
O-Subject: [RHEL5 U2 PATCH 2/8] s390 - zfcp: Deadlock when adding invalid LUN
Bugzilla: 412841
RH-Acked-by: Pete Zaitcev <zaitcev@redhat.com>

Description
============

After adding an invalid LUN to zfcp, this LUN can not be removed again,
the sysfs write for removal returs ENODEV.

The unit_add calls internally scsi_add_device, this function calls the
zfcp slave_destroy handler after determining that the unit does
not exist.
The zfcp slave_destroy handler waits for the scsi_add_device call to complete and
we have a deadlock.

The problem is fixed removing the wait in the zfcp slave_destroy handler. It was
not required anyway and this resolves the deadlock.

Bugzilla
=========

BZ 412841
https://bugzilla.redhat.com/show_bug.cgi?id=412841

Upstream status of the patch:
=============================
The patch is already upstream in the scsi-misc tree, commit
d858b526c5e638b0f29d05eb885df65e18ec6cc8

Test status:
============
Kernel with patch was built and successfully tested

Please ACK.

With best regards,

Hans

diff --git a/drivers/s390/scsi/zfcp_scsi.c b/drivers/s390/scsi/zfcp_scsi.c
index af0327d..40f385c 100644
--- a/drivers/s390/scsi/zfcp_scsi.c
+++ b/drivers/s390/scsi/zfcp_scsi.c
@@ -182,9 +182,6 @@ static void zfcp_scsi_slave_destroy(struct scsi_device *sdpnt)
 
 	if (unit) {
 		zfcp_erp_wait(unit->port->adapter);
-		wait_event(unit->scsi_scan_wq,
-			   atomic_test_mask(ZFCP_STATUS_UNIT_SCSI_WORK_PENDING,
-					    &unit->status) == 0);
 		atomic_clear_mask(ZFCP_STATUS_UNIT_REGISTERED, &unit->status);
 		sdpnt->hostdata = NULL;
 		unit->device = NULL;