Patch "iscsi-target: Fix delayed logout processing greater than SECONDS_FOR_LOGOUT_COMP" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

iscsi-target: Fix delayed logout processing greater than SECONDS_FOR_LOGOUT_COMP

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
iscsi-target-fix-delayed-logout-processing-greater-than-seconds_for_logout_comp.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Nicholas Bellinger <[email protected]>
Date: Sat, 3 Jun 2017 05:35:47 -0700
Subject: iscsi-target: Fix delayed logout processing greater than SECONDS_FOR_LOGOUT_COMP

From: Nicholas Bellinger <[email protected]>

commit 105fa2f44e504c830697b0c794822112d79808dc upstream.

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.

---
 drivers/target/iscsi/iscsi_target.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

@@ -4431,8 +4431,11 @@ static void iscsit_logout_post_handler_c
 	 * 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);

@@ -4448,8 +4451,11 @@ static void iscsit_logout_post_handler_s
 {
 	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);

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/iscsi-target-reject-immediate-data-underflow-larger-than-scsi-transfer-length.patch queue-4.9/iscsi-target-fix-delayed-logout-processing-greater-than-seconds_for_logout_comp.patch queue-4.9/target-fix-kref-refcount-underflow-in-transport_cmd_finish_abort.patch