linux-kernel - [PATCH 3.16.y-ckt 008/130] iscsi-target: Fix iser explicit logout TX kthread leak

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Message-Id: <1441372118-5933-9-git-send-email-luis.henriques@canonical.com>
Date:	Fri,  4 Sep 2015 14:06:36 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Sagi Grimberg <sagig@...lanox.com>,
	Nicholas Bellinger <nab@...ux-iscsi.org>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 008/130] iscsi-target: Fix iser explicit logout TX kthread leak

3.16.7-ckt17 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nicholas Bellinger <nab@...ux-iscsi.org>

commit 007d038bdf95ccfe2491d0078be54040d110fd06 upstream.

This patch fixes a regression introduced with the following commit
in v4.0-rc1 code, where an explicit iser-target logout would result
in ->tx_thread_active being incorrectly cleared by the logout post
handler, and subsequent TX kthread leak:

    commit 88dcd2dab5c23b1c9cfc396246d8f476c872f0ca
    Author: Nicholas Bellinger <nab@...ux-iscsi.org>
    Date:   Thu Feb 26 22:19:15 2015 -0800

        iscsi-target: Convert iscsi_thread_set usage to kthread.h

To address this bug, change iscsit_logout_post_handler_closesession()
and iscsit_logout_post_handler_samecid() to only cmpxchg() on
->tx_thread_active for traditional iscsi/tcp connections.

This is required because iscsi/tcp connections are invoking logout
post handler logic directly from TX kthread context, while iser
connections are invoking logout post handler logic from a seperate
workqueue context.

Cc: Sagi Grimberg <sagig@...lanox.com>
Signed-off-by: Nicholas Bellinger <nab@...ux-iscsi.org>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 drivers/target/iscsi/iscsi_target.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index cc401d217406..ce87bdcb1843 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -4515,7 +4515,18 @@ static void iscsit_logout_post_handler_closesession(
 	struct iscsi_conn *conn)
 {
 	struct iscsi_session *sess = conn->sess;
-	int sleep = cmpxchg(&conn->tx_thread_active, true, false);
+	int sleep = 1;
+	/*
+	 * Traditional iscsi/tcp will invoke this logic from TX thread
+	 * context during session logout, so clear tx_thread_active and
+	 * sleep if iscsit_close_connection() has not already occured.
+	 *
+	 * Since iser-target invokes this logic from it's own workqueue,
+	 * always sleep waiting for RX/TX thread shutdown to complete
+	 * within iscsit_close_connection().
+	 */
+	if (conn->conn_transport->transport_type == ISCSI_TCP)
+		sleep = cmpxchg(&conn->tx_thread_active, true, false);
 
 	atomic_set(&conn->conn_logout_remove, 0);
 	complete(&conn->conn_logout_comp);
@@ -4529,7 +4540,10 @@ static void iscsit_logout_post_handler_closesession(
 static void iscsit_logout_post_handler_samecid(
 	struct iscsi_conn *conn)
 {
-	int sleep = cmpxchg(&conn->tx_thread_active, true, false);
+	int sleep = 1;
+
+	if (conn->conn_transport->transport_type == ISCSI_TCP)
+		sleep = cmpxchg(&conn->tx_thread_active, true, false);
 
 	atomic_set(&conn->conn_logout_remove, 0);
 	complete(&conn->conn_logout_comp);
--
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