From: Maurizio Lombardi mlombard@redhat.com
[ Upstream commit 57c46e9f33da530a2485fa01aa27b6d18c28c796 ]
A number of hangs have been reported against the target driver; they are due to the fact that multiple threads may try to destroy the iscsi session at the same time. This may be reproduced for example when a "targetcli iscsi/iqn.../tpg1 disable" command is executed while a logout operation is underway.
When this happens, two or more threads may end up sleeping and waiting for iscsit_close_connection() to execute "complete(session_wait_comp)". Only one of the threads will wake up and proceed to destroy the session structure, the remaining threads will hang forever.
Note that if the blocked threads are somehow forced to wake up with complete_all(), they will try to free the same iscsi session structure destroyed by the first thread, causing double frees, memory corruptions etc...
With this patch, the threads that want to destroy the iscsi session will increase the session refcount and will set the "session_close" flag to 1; then they wait for the driver to close the remaining active connections. When the last connection is closed, iscsit_close_connection() will wake up all the threads and will wait for the session's refcount to reach zero; when this happens, iscsit_close_connection() will destroy the session structure because no one is referencing it anymore.
INFO: task targetcli:5971 blocked for more than 120 seconds. Tainted: P OE 4.15.0-72-generic #81~16.04.1 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. targetcli D 0 5971 1 0x00000080 Call Trace: __schedule+0x3d6/0x8b0 ? vprintk_func+0x44/0xe0 schedule+0x36/0x80 schedule_timeout+0x1db/0x370 ? __dynamic_pr_debug+0x8a/0xb0 wait_for_completion+0xb4/0x140 ? wake_up_q+0x70/0x70 iscsit_free_session+0x13d/0x1a0 [iscsi_target_mod] iscsit_release_sessions_for_tpg+0x16b/0x1e0 [iscsi_target_mod] iscsit_tpg_disable_portal_group+0xca/0x1c0 [iscsi_target_mod] lio_target_tpg_enable_store+0x66/0xe0 [iscsi_target_mod] configfs_write_file+0xb9/0x120 __vfs_write+0x1b/0x40 vfs_write+0xb8/0x1b0 SyS_write+0x5c/0xe0 do_syscall_64+0x73/0x130 entry_SYSCALL_64_after_hwframe+0x3d/0xa2
Link: https://lore.kernel.org/r/20200313170656.9716-3-mlombard@redhat.com Reported-by: Matt Coleman mcoleman@datto.com Tested-by: Matt Coleman mcoleman@datto.com Tested-by: Rahul Kundu rahul.kundu@chelsio.com Signed-off-by: Maurizio Lombardi mlombard@redhat.com Signed-off-by: Martin K. Petersen martin.petersen@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/target/iscsi/iscsi_target.c | 35 ++++++++++++++++----------- drivers/target/iscsi/iscsi_target_configfs.c | 5 +++ drivers/target/iscsi/iscsi_target_login.c | 5 ++- include/target/iscsi/iscsi_target_core.h | 2 - 4 files changed, 30 insertions(+), 17 deletions(-)
--- a/drivers/target/iscsi/iscsi_target.c +++ b/drivers/target/iscsi/iscsi_target.c @@ -4321,30 +4321,37 @@ int iscsit_close_connection( if (!atomic_read(&sess->session_reinstatement) && atomic_read(&sess->session_fall_back_to_erl0)) { spin_unlock_bh(&sess->conn_lock); + complete_all(&sess->session_wait_comp); iscsit_close_session(sess);
return 0; } else if (atomic_read(&sess->session_logout)) { pr_debug("Moving to TARG_SESS_STATE_FREE.\n"); sess->session_state = TARG_SESS_STATE_FREE; - spin_unlock_bh(&sess->conn_lock);
- if (atomic_read(&sess->sleep_on_sess_wait_comp)) - complete(&sess->session_wait_comp); + if (atomic_read(&sess->session_close)) { + spin_unlock_bh(&sess->conn_lock); + complete_all(&sess->session_wait_comp); + iscsit_close_session(sess); + } else { + spin_unlock_bh(&sess->conn_lock); + }
return 0; } else { pr_debug("Moving to TARG_SESS_STATE_FAILED.\n"); sess->session_state = TARG_SESS_STATE_FAILED;
- if (!atomic_read(&sess->session_continuation)) { - spin_unlock_bh(&sess->conn_lock); + if (!atomic_read(&sess->session_continuation)) iscsit_start_time2retain_handler(sess); - } else - spin_unlock_bh(&sess->conn_lock);
- if (atomic_read(&sess->sleep_on_sess_wait_comp)) - complete(&sess->session_wait_comp); + if (atomic_read(&sess->session_close)) { + spin_unlock_bh(&sess->conn_lock); + complete_all(&sess->session_wait_comp); + iscsit_close_session(sess); + } else { + spin_unlock_bh(&sess->conn_lock); + }
return 0; } @@ -4453,9 +4460,9 @@ static void iscsit_logout_post_handler_c complete(&conn->conn_logout_comp);
iscsit_dec_conn_usage_count(conn); + atomic_set(&sess->session_close, 1); iscsit_stop_session(sess, sleep, sleep); iscsit_dec_session_usage_count(sess); - iscsit_close_session(sess); }
static void iscsit_logout_post_handler_samecid( @@ -4600,8 +4607,6 @@ void iscsit_stop_session( int is_last;
spin_lock_bh(&sess->conn_lock); - if (session_sleep) - atomic_set(&sess->sleep_on_sess_wait_comp, 1);
if (connection_sleep) { list_for_each_entry_safe(conn, conn_tmp, &sess->sess_conn_list, @@ -4659,12 +4664,15 @@ int iscsit_release_sessions_for_tpg(stru spin_lock(&sess->conn_lock); if (atomic_read(&sess->session_fall_back_to_erl0) || atomic_read(&sess->session_logout) || + atomic_read(&sess->session_close) || (sess->time2retain_timer_flags & ISCSI_TF_EXPIRED)) { spin_unlock(&sess->conn_lock); continue; } + iscsit_inc_session_usage_count(sess); atomic_set(&sess->session_reinstatement, 1); atomic_set(&sess->session_fall_back_to_erl0, 1); + atomic_set(&sess->session_close, 1); spin_unlock(&sess->conn_lock);
list_move_tail(&se_sess->sess_list, &free_list); @@ -4674,8 +4682,9 @@ int iscsit_release_sessions_for_tpg(stru list_for_each_entry_safe(se_sess, se_sess_tmp, &free_list, sess_list) { sess = (struct iscsi_session *)se_sess->fabric_sess_ptr;
+ list_del_init(&se_sess->sess_list); iscsit_stop_session(sess, 1, 1); - iscsit_close_session(sess); + iscsit_dec_session_usage_count(sess); session_count++; }
--- a/drivers/target/iscsi/iscsi_target_configfs.c +++ b/drivers/target/iscsi/iscsi_target_configfs.c @@ -1527,20 +1527,23 @@ static void lio_tpg_close_session(struct spin_lock(&sess->conn_lock); if (atomic_read(&sess->session_fall_back_to_erl0) || atomic_read(&sess->session_logout) || + atomic_read(&sess->session_close) || (sess->time2retain_timer_flags & ISCSI_TF_EXPIRED)) { spin_unlock(&sess->conn_lock); spin_unlock_bh(&se_tpg->session_lock); return; } + iscsit_inc_session_usage_count(sess); atomic_set(&sess->session_reinstatement, 1); atomic_set(&sess->session_fall_back_to_erl0, 1); + atomic_set(&sess->session_close, 1); spin_unlock(&sess->conn_lock);
iscsit_stop_time2retain_timer(sess); spin_unlock_bh(&se_tpg->session_lock);
iscsit_stop_session(sess, 1, 1); - iscsit_close_session(sess); + iscsit_dec_session_usage_count(sess); }
static u32 lio_tpg_get_inst_index(struct se_portal_group *se_tpg) --- a/drivers/target/iscsi/iscsi_target_login.c +++ b/drivers/target/iscsi/iscsi_target_login.c @@ -195,6 +195,7 @@ int iscsi_check_for_session_reinstatemen spin_lock(&sess_p->conn_lock); if (atomic_read(&sess_p->session_fall_back_to_erl0) || atomic_read(&sess_p->session_logout) || + atomic_read(&sess_p->session_close) || (sess_p->time2retain_timer_flags & ISCSI_TF_EXPIRED)) { spin_unlock(&sess_p->conn_lock); continue; @@ -205,6 +206,7 @@ int iscsi_check_for_session_reinstatemen (sess_p->sess_ops->SessionType == sessiontype))) { atomic_set(&sess_p->session_reinstatement, 1); atomic_set(&sess_p->session_fall_back_to_erl0, 1); + atomic_set(&sess_p->session_close, 1); spin_unlock(&sess_p->conn_lock); iscsit_inc_session_usage_count(sess_p); iscsit_stop_time2retain_timer(sess_p); @@ -229,7 +231,6 @@ int iscsi_check_for_session_reinstatemen if (sess->session_state == TARG_SESS_STATE_FAILED) { spin_unlock_bh(&sess->conn_lock); iscsit_dec_session_usage_count(sess); - iscsit_close_session(sess); return 0; } spin_unlock_bh(&sess->conn_lock); @@ -237,7 +238,6 @@ int iscsi_check_for_session_reinstatemen iscsit_stop_session(sess, 1, 1); iscsit_dec_session_usage_count(sess);
- iscsit_close_session(sess); return 0; }
@@ -525,6 +525,7 @@ static int iscsi_login_non_zero_tsih_s2( sess_p = (struct iscsi_session *)se_sess->fabric_sess_ptr; if (atomic_read(&sess_p->session_fall_back_to_erl0) || atomic_read(&sess_p->session_logout) || + atomic_read(&sess_p->session_close) || (sess_p->time2retain_timer_flags & ISCSI_TF_EXPIRED)) continue; if (!memcmp(sess_p->isid, pdu->isid, 6) && --- a/include/target/iscsi/iscsi_target_core.h +++ b/include/target/iscsi/iscsi_target_core.h @@ -671,7 +671,7 @@ struct iscsi_session { atomic_t session_logout; atomic_t session_reinstatement; atomic_t session_stop_active; - atomic_t sleep_on_sess_wait_comp; + atomic_t session_close; /* connection list */ struct list_head sess_conn_list; struct list_head cr_active_list;