Patchwork [3.5.y.z,extended,stable] Patch "qla2xxx: Test and clear FCPORT_UPDATE_NEEDED atomically." has been added to staging queue

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Submitter Herton Ronaldo Krzesinski
Date Jan. 7, 2013, 8:35 p.m.
Message ID <1357590955-19994-1-git-send-email-herton.krzesinski@canonical.com>
Download mbox | patch
Permalink /patch/210178/
State New
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Herton Ronaldo Krzesinski - Jan. 7, 2013, 8:35 p.m.
This is a note to let you know that I have just added a patch titled

    qla2xxx: Test and clear FCPORT_UPDATE_NEEDED atomically.

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Herton

------

From dd9cbd631d05876ee9e3fc9713c39f1a75fc7417 Mon Sep 17 00:00:00 2001
From: David Jeffery <djeffery@redhat.com>
Date: Wed, 21 Nov 2012 02:39:54 -0500
Subject: [PATCH] qla2xxx: Test and clear FCPORT_UPDATE_NEEDED atomically.

commit a394aac88506159e047630fc90dc2242568382d8 upstream.

When the qla2xxx driver loses access to multiple, remote ports, there is a race
condition which can occur which will keep the request stuck on a scsi request
queue indefinitely.

This bad state occurred do to a race condition with how the FCPORT_UPDATE_NEEDED
bit is set in qla2x00_schedule_rport_del(), and how it is cleared in
qla2x00_do_dpc().  The problem port has its drport pointer set, but it has never
been processed by the driver to inform the fc transport that the port has been
lost.  qla2x00_schedule_rport_del() sets drport, and then sets the
FCPORT_UPDATE_NEEDED bit.  In qla2x00_do_dpc(), the port lists are walked and
any drport pointer is handled and the fc transport informed of the port loss,
then the FCPORT_UPDATE_NEEDED bit is cleared.  This leaves a race where the
dpc thread is processing one port removal, another port removal is marked
with a call to qla2x00_schedule_rport_del(), and the dpc thread clears the
bit for both removals, even though only the first removal was actually
handled.  Until another event occurs to set FCPORT_UPDATE_NEEDED, the later
port removal is never finished and qla2xxx stays in a bad state which causes
requests to become stuck on request queues.

This patch updates the driver to test and clear FCPORT_UPDATE_NEEDED
atomically.  This ensures the port state changes are processed and not lost.

Signed-off-by: David Jeffery <djeffery@redhat.com>
Signed-off-by: Chad Dupuis <chad.dupuis@qlogic.com>
Signed-off-by: Saurav Kashyap <saurav.kashyap@qlogic.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
---
 drivers/scsi/qla2xxx/qla_os.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--
1.7.9.5

Patch

diff --git a/drivers/scsi/qla2xxx/qla_os.c b/drivers/scsi/qla2xxx/qla_os.c
index 6d1d873..f6f555a 100644
--- a/drivers/scsi/qla2xxx/qla_os.c
+++ b/drivers/scsi/qla2xxx/qla_os.c
@@ -3801,9 +3801,9 @@  qla2x00_do_dpc(void *data)
 			    "ISP abort end.\n");
 		}

-		if (test_bit(FCPORT_UPDATE_NEEDED, &base_vha->dpc_flags)) {
+		if (test_and_clear_bit(FCPORT_UPDATE_NEEDED,
+		    &base_vha->dpc_flags)) {
 			qla2x00_update_fcports(base_vha);
-			clear_bit(FCPORT_UPDATE_NEEDED, &base_vha->dpc_flags);
 		}

 		if (test_bit(SCR_PENDING, &base_vha->dpc_flags)) {