This is a note to let you know that I've just added the patch titled
iscsi-target: Fix missed wakeup race in TX thread
to the 3.4-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-missed-wakeup-race-in-tx-thread.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From d5627acba9ae584cf4928af19f7ddf5f6837de32 Mon Sep 17 00:00:00 2001
From: Roland Dreier <[email protected]>
Date: Wed, 31 Oct 2012 09:16:46 -0700
Subject: iscsi-target: Fix missed wakeup race in TX thread
From: Roland Dreier <[email protected]>
commit d5627acba9ae584cf4928af19f7ddf5f6837de32 upstream.
The sleeping code in iscsi_target_tx_thread() is susceptible to the classic
missed wakeup race:
- TX thread finishes handle_immediate_queue() and handle_response_queue(),
thinks both queues are empty.
- Another thread adds a queue entry and does wake_up_process(), which does
nothing because the TX thread is still awake.
- TX thread does schedule_timeout() and sleeps forever.
In practice this can kill an iSCSI connection if for example an initiator
does single-threaded writes and the target misses the wakeup window when
queueing an R2T; in this case the connection will be stuck until the
initiator loses patience and does some task management operation (or kills
the connection entirely).
Fix this by converting to wait_event_interruptible(), which does not
suffer from this sort of race.
Signed-off-by: Roland Dreier <[email protected]>
Cc: Andy Grover <[email protected]>
Cc: Hannes Reinecke <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Signed-off-by: Nicholas Bellinger <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
drivers/target/iscsi/iscsi_target.c | 4 +++-
drivers/target/iscsi/iscsi_target_core.h | 1 +
drivers/target/iscsi/iscsi_target_login.c | 1 +
drivers/target/iscsi/iscsi_target_util.c | 22 ++++++++++++++++++++--
drivers/target/iscsi/iscsi_target_util.h | 1 +
5 files changed, 26 insertions(+), 3 deletions(-)
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -3514,7 +3514,9 @@ restart:
*/
iscsit_thread_check_cpumask(conn, current, 1);
- schedule_timeout_interruptible(MAX_SCHEDULE_TIMEOUT);
+ wait_event_interruptible(conn->queues_wq,
+ !iscsit_conn_all_queues_empty(conn) ||
+ ts->status == ISCSI_THREAD_SET_RESET);
if ((ts->status == ISCSI_THREAD_SET_RESET) ||
signal_pending(current))
--- a/drivers/target/iscsi/iscsi_target_core.h
+++ b/drivers/target/iscsi/iscsi_target_core.h
@@ -491,6 +491,7 @@ struct iscsi_tmr_req {
};
struct iscsi_conn {
+ wait_queue_head_t queues_wq;
/* Authentication Successful for this connection */
u8 auth_complete;
/* State connection is currently in */
--- a/drivers/target/iscsi/iscsi_target_login.c
+++ b/drivers/target/iscsi/iscsi_target_login.c
@@ -45,6 +45,7 @@ extern spinlock_t sess_idr_lock;
static int iscsi_login_init_conn(struct iscsi_conn *conn)
{
+ init_waitqueue_head(&conn->queues_wq);
INIT_LIST_HEAD(&conn->conn_list);
INIT_LIST_HEAD(&conn->conn_cmd_list);
INIT_LIST_HEAD(&conn->immed_queue_list);
--- a/drivers/target/iscsi/iscsi_target_util.c
+++ b/drivers/target/iscsi/iscsi_target_util.c
@@ -656,7 +656,7 @@ void iscsit_add_cmd_to_immediate_queue(
atomic_set(&conn->check_immediate_queue, 1);
spin_unlock_bh(&conn->immed_queue_lock);
- wake_up_process(conn->thread_set->tx_thread);
+ wake_up(&conn->queues_wq);
}
struct iscsi_queue_req *iscsit_get_cmd_from_immediate_queue(struct iscsi_conn
*conn)
@@ -730,7 +730,7 @@ void iscsit_add_cmd_to_response_queue(
atomic_inc(&cmd->response_queue_count);
spin_unlock_bh(&conn->response_queue_lock);
- wake_up_process(conn->thread_set->tx_thread);
+ wake_up(&conn->queues_wq);
}
struct iscsi_queue_req *iscsit_get_cmd_from_response_queue(struct iscsi_conn
*conn)
@@ -784,6 +784,24 @@ static void iscsit_remove_cmd_from_respo
}
}
+bool iscsit_conn_all_queues_empty(struct iscsi_conn *conn)
+{
+ bool empty;
+
+ spin_lock_bh(&conn->immed_queue_lock);
+ empty = list_empty(&conn->immed_queue_list);
+ spin_unlock_bh(&conn->immed_queue_lock);
+
+ if (!empty)
+ return empty;
+
+ spin_lock_bh(&conn->response_queue_lock);
+ empty = list_empty(&conn->response_queue_list);
+ spin_unlock_bh(&conn->response_queue_lock);
+
+ return empty;
+}
+
void iscsit_free_queue_reqs_for_conn(struct iscsi_conn *conn)
{
struct iscsi_queue_req *qr, *qr_tmp;
--- a/drivers/target/iscsi/iscsi_target_util.h
+++ b/drivers/target/iscsi/iscsi_target_util.h
@@ -28,6 +28,7 @@ extern struct iscsi_queue_req *iscsit_ge
extern void iscsit_add_cmd_to_response_queue(struct iscsi_cmd *, struct
iscsi_conn *, u8);
extern struct iscsi_queue_req *iscsit_get_cmd_from_response_queue(struct
iscsi_conn *);
extern void iscsit_remove_cmd_from_tx_queues(struct iscsi_cmd *, struct
iscsi_conn *);
+extern bool iscsit_conn_all_queues_empty(struct iscsi_conn *);
extern void iscsit_free_queue_reqs_for_conn(struct iscsi_conn *);
extern void iscsit_release_cmd(struct iscsi_cmd *);
extern void iscsit_free_cmd(struct iscsi_cmd *);
Patches currently in stable-queue which might be from [email protected] are
queue-3.4/target-avoid-integer-overflow-in-se_dev_align_max_sectors.patch
queue-3.4/target-fix-incorrect-usage-of-nested-irq-spinlocks-in-abort_task-path.patch
queue-3.4/iscsi-target-fix-missed-wakeup-race-in-tx-thread.patch
queue-3.4/target-don-t-return-success-from-module_init-if-setup-fails.patch
--
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