linux-kernel - [PATCH] iscsi-target: Fix delayed logout processing greater than SECONDS_FOR_LOGOUT

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Message-Id: <1496525574-26784-1-git-send-email-nab@linux-iscsi.org>
Date:   Sat,  3 Jun 2017 21:32:54 +0000
From:   "Nicholas A. Bellinger" <nab@...ux-iscsi.org>
To:     target-devel <target-devel@...r.kernel.org>
Cc:     linux-scsi <linux-scsi@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Nicholas Bellinger <nab@...ux-iscsi.org>,
        Mike Christie <mchristi@...hat.com>,
        Hannes Reinecke <hare@...e.de>,
        Sagi Grimberg <sagig@...lanox.com>
Subject: [PATCH] iscsi-target: Fix delayed logout processing greater than SECONDS_FOR_LOGOUT_COMP

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

This patch fixes a BUG() in iscsit_close_session() that could be
triggered when iscsit_logout_post_handler() execution from within
tx thread context was not run for more than SECONDS_FOR_LOGOUT_COMP
(15 seconds), and the TCP connection didn't already close before
then forcing tx thread context to automatically exit.

This would manifest itself during explicit logout as:

[33206.974254] 1 connection(s) still exist for iSCSI session to iqn.1993-08.org.debian:01:3f5523242179
[33206.980184] INFO: NMI handler (kgdb_nmi_handler) took too long to run: 2100.772 msecs
[33209.078643] ------------[ cut here ]------------
[33209.078646] kernel BUG at drivers/target/iscsi/iscsi_target.c:4346!

Normally when explicit logout attempt fails, the tx thread context
exits and iscsit_close_connection() from rx thread context does the
extra cleanup once it detects conn->conn_logout_remove has not been
cleared by the logout type specific post handlers.

To address this special case, if the logout post handler in tx thread
context detects conn->tx_thread_active has already been cleared, simply
return and exit in order for existing iscsit_close_connection()
logic from rx thread context do failed logout cleanup.

Reported-by: Bart Van Assche <bart.vanassche@...disk.com>
Cc: Mike Christie <mchristi@...hat.com>
Cc: Hannes Reinecke <hare@...e.de>
Cc: Sagi Grimberg <sagig@...lanox.com>
Cc: stable@...r.kernel.org # 3.14+
Signed-off-by: Nicholas Bellinger <nab@...ux-iscsi.org>
---
 drivers/target/iscsi/iscsi_target.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index 0d8f815..c025451 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -4423,8 +4423,11 @@ static void iscsit_logout_post_handler_closesession(
 	 * always sleep waiting for RX/TX thread shutdown to complete
 	 * within iscsit_close_connection().
 	 */
-	if (!conn->conn_transport->rdma_shutdown)
+	if (!conn->conn_transport->rdma_shutdown) {
 		sleep = cmpxchg(&conn->tx_thread_active, true, false);
+		if (!sleep)
+			return;
+	}

 	atomic_set(&conn->conn_logout_remove, 0);
 	complete(&conn->conn_logout_comp);
@@ -4440,8 +4443,11 @@ static void iscsit_logout_post_handler_samecid(
 {
 	int sleep = 1;

-	if (!conn->conn_transport->rdma_shutdown)
+	if (!conn->conn_transport->rdma_shutdown) {
 		sleep = cmpxchg(&conn->tx_thread_active, true, false);
+		if (!sleep)
+			return;
+	}

 	atomic_set(&conn->conn_logout_remove, 0);
 	complete(&conn->conn_logout_comp);
-- 
1.9.1