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authorRoland Dreier <roland@purestorage.com>2012-10-31 20:16:46 +0400
committerNicholas Bellinger <nab@linux-iscsi.org>2012-11-01 11:38:44 +0400
commitd5627acba9ae584cf4928af19f7ddf5f6837de32 (patch)
tree4247438e4a6ab7ef76c68a6d35093db95eca1451 /drivers
parent3e03989b5868acf69a391a424dc71fcd6cc48167 (diff)
downloadlinux-d5627acba9ae584cf4928af19f7ddf5f6837de32.tar.xz
iscsi-target: Fix missed wakeup race in TX thread
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 <roland@purestorage.com> Cc: Andy Grover <agrover@redhat.com> Cc: Hannes Reinecke <hare@suse.de> Cc: Christoph Hellwig <hch@lst.de> Cc: stable@vger.kernel.org Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/target/iscsi/iscsi_target.c4
-rw-r--r--drivers/target/iscsi/iscsi_target_core.h1
-rw-r--r--drivers/target/iscsi/iscsi_target_login.c1
-rw-r--r--drivers/target/iscsi/iscsi_target_util.c22
-rw-r--r--drivers/target/iscsi/iscsi_target_util.h1
5 files changed, 26 insertions, 3 deletions
diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index d6ce2182e672..035c2c762537 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -3719,7 +3719,9 @@ 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))
diff --git a/drivers/target/iscsi/iscsi_target_core.h b/drivers/target/iscsi/iscsi_target_core.h
index 2ba9f9b9435c..21048dbf7d13 100644
--- a/drivers/target/iscsi/iscsi_target_core.h
+++ b/drivers/target/iscsi/iscsi_target_core.h
@@ -486,6 +486,7 @@ 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 */
diff --git a/drivers/target/iscsi/iscsi_target_login.c b/drivers/target/iscsi/iscsi_target_login.c
index cdc8a10939c3..f8dbec05d5e5 100644
--- a/drivers/target/iscsi/iscsi_target_login.c
+++ b/drivers/target/iscsi/iscsi_target_login.c
@@ -41,6 +41,7 @@
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);
diff --git a/drivers/target/iscsi/iscsi_target_util.c b/drivers/target/iscsi/iscsi_target_util.c
index afd98ccd40ae..1a91195ab619 100644
--- a/drivers/target/iscsi/iscsi_target_util.c
+++ b/drivers/target/iscsi/iscsi_target_util.c
@@ -488,7 +488,7 @@ 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)
@@ -562,7 +562,7 @@ 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)
@@ -616,6 +616,24 @@ static void iscsit_remove_cmd_from_response_queue(
}
}
+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;
diff --git a/drivers/target/iscsi/iscsi_target_util.h b/drivers/target/iscsi/iscsi_target_util.h
index 44054bd35437..894d0f837924 100644
--- a/drivers/target/iscsi/iscsi_target_util.h
+++ b/drivers/target/iscsi/iscsi_target_util.h
@@ -25,6 +25,7 @@ extern struct iscsi_queue_req *iscsit_get_cmd_from_immediate_queue(struct iscsi_
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 *);