4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Bart Van Assche bvanassche@acm.org
commit 32e36bfbcf31452a854263e7c7f32fbefc4b44d8 upstream.
When using SCSI passthrough in combination with the iSCSI target driver then cmd->t_state_lock may be obtained from interrupt context. Hence, all code that obtains cmd->t_state_lock from thread context must disable interrupts first. This patch avoids that lockdep reports the following:
WARNING: inconsistent lock state 4.18.0-dbg+ #1 Not tainted -------------------------------- inconsistent {HARDIRQ-ON-W} -> {IN-HARDIRQ-W} usage. iscsi_ttx/1800 [HC1[1]:SC0[2]:HE0:SE0] takes: 000000006e7b0ceb (&(&cmd->t_state_lock)->rlock){?...}, at: target_complete_cmd+0x47/0x2c0 [target_core_mod] {HARDIRQ-ON-W} state was registered at: lock_acquire+0xd2/0x260 _raw_spin_lock+0x32/0x50 iscsit_close_connection+0x97e/0x1020 [iscsi_target_mod] iscsit_take_action_for_connection_exit+0x108/0x200 [iscsi_target_mod] iscsi_target_rx_thread+0x180/0x190 [iscsi_target_mod] kthread+0x1cf/0x1f0 ret_from_fork+0x24/0x30 irq event stamp: 1281 hardirqs last enabled at (1279): [<ffffffff970ade79>] __local_bh_enable_ip+0xa9/0x160 hardirqs last disabled at (1281): [<ffffffff97a008a5>] interrupt_entry+0xb5/0xd0 softirqs last enabled at (1278): [<ffffffff977cd9a1>] lock_sock_nested+0x51/0xc0 softirqs last disabled at (1280): [<ffffffffc07a6e04>] ip6_finish_output2+0x124/0xe40 [ipv6]
other info that might help us debug this: Possible unsafe locking scenario:
CPU0 ---- lock(&(&cmd->t_state_lock)->rlock); <Interrupt> lock(&(&cmd->t_state_lock)->rlock);
--- drivers/target/iscsi/iscsi_target.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/drivers/target/iscsi/iscsi_target.c +++ b/drivers/target/iscsi/iscsi_target.c @@ -4232,9 +4232,9 @@ static void iscsit_release_commands_from struct se_cmd *se_cmd = &cmd->se_cmd;
if (se_cmd->se_tfo != NULL) { - spin_lock(&se_cmd->t_state_lock); + spin_lock_irq(&se_cmd->t_state_lock); se_cmd->transport_state |= CMD_T_FABRIC_STOP; - spin_unlock(&se_cmd->t_state_lock); + spin_unlock_irq(&se_cmd->t_state_lock); } } spin_unlock_bh(&conn->cmd_lock);