queue-4.19/scsi-target-iscsi-avoid-iscsit_release_commands_from_conn-deadlock.patch

   1 From 32e36bfbcf31452a854263e7c7f32fbefc4b44d8 Mon Sep 17 00:00:00 2001
   2 From: Bart Van Assche <bvanassche@acm.org>
   3 Date: Fri, 25 Jan 2019 10:34:56 -0800
   4 Subject: scsi: target/iscsi: Avoid iscsit_release_commands_from_conn() deadlock
   5
   6 From: Bart Van Assche <bvanassche@acm.org>
   7
   8 commit 32e36bfbcf31452a854263e7c7f32fbefc4b44d8 upstream.
   9
  10 When using SCSI passthrough in combination with the iSCSI target driver
  11 then cmd->t_state_lock may be obtained from interrupt context. Hence, all
  12 code that obtains cmd->t_state_lock from thread context must disable
  13 interrupts first. This patch avoids that lockdep reports the following:
  14
  15 WARNING: inconsistent lock state
  16 4.18.0-dbg+ #1 Not tainted
  17 --------------------------------
  18 inconsistent {HARDIRQ-ON-W} -> {IN-HARDIRQ-W} usage.
  19 iscsi_ttx/1800 [HC1[1]:SC0[2]:HE0:SE0] takes:
  20 000000006e7b0ceb (&(&cmd->t_state_lock)->rlock){?...}, at: target_complete_cmd+0x47/0x2c0 [target_core_mod]
  21 {HARDIRQ-ON-W} state was registered at:
  22  lock_acquire+0xd2/0x260
  23  _raw_spin_lock+0x32/0x50
  24  iscsit_close_connection+0x97e/0x1020 [iscsi_target_mod]
  25  iscsit_take_action_for_connection_exit+0x108/0x200 [iscsi_target_mod]
  26  iscsi_target_rx_thread+0x180/0x190 [iscsi_target_mod]
  27  kthread+0x1cf/0x1f0
  28  ret_from_fork+0x24/0x30
  29 irq event stamp: 1281
  30 hardirqs last  enabled at (1279): [<ffffffff970ade79>] __local_bh_enable_ip+0xa9/0x160
  31 hardirqs last disabled at (1281): [<ffffffff97a008a5>] interrupt_entry+0xb5/0xd0
  32 softirqs last  enabled at (1278): [<ffffffff977cd9a1>] lock_sock_nested+0x51/0xc0
  33 softirqs last disabled at (1280): [<ffffffffc07a6e04>] ip6_finish_output2+0x124/0xe40 [ipv6]
  34
  35 other info that might help us debug this:
  36 Possible unsafe locking scenario:
  37
  38       CPU0
  39       ----
  40  lock(&(&cmd->t_state_lock)->rlock);
  41  <Interrupt>
  42    lock(&(&cmd->t_state_lock)->rlock);
  43
  44 ---
  45  drivers/target/iscsi/iscsi_target.c |    4 ++--
  46  1 file changed, 2 insertions(+), 2 deletions(-)
  47
  48 --- a/drivers/target/iscsi/iscsi_target.c
  49 +++ b/drivers/target/iscsi/iscsi_target.c
  50 @@ -4045,9 +4045,9 @@ static void iscsit_release_commands_from
  51                 struct se_cmd *se_cmd = &cmd->se_cmd;
  52
  53                 if (se_cmd->se_tfo != NULL) {
  54 -                       spin_lock(&se_cmd->t_state_lock);
  55 +                       spin_lock_irq(&se_cmd->t_state_lock);
  56                         se_cmd->transport_state |= CMD_T_FABRIC_STOP;
  57 -                       spin_unlock(&se_cmd->t_state_lock);
  58 +                       spin_unlock_irq(&se_cmd->t_state_lock);
  59                 }
  60         }
  61         spin_unlock_bh(&conn->cmd_lock);