On Wed, 16 Aug 2023, Chengfeng Ye wrote:
There is a long call chain that &fip->ctlr_lock is acquired by isr fnic_isr_msix_wq_copy() under hard irq context. Thus other process context code acquiring the lock should disable irq, otherwise deadlock could happen if the irq preempt the execution while the lock is held in process context on the same CPU. [ISR] fnic_isr_msix_wq_copy() -> fnic_wq_copy_cmpl_handler() -> fnic_fcpio_cmpl_handler() -> fnic_fcpio_flogi_reg_cmpl_handler() -> fnic_flush_tx() -> fnic_send_frame() -> fcoe_ctlr_els_send() -> spin_lock_bh(&fip->ctlr_lock) [Process Context] 1. fcoe_ctlr_timer_work() -> fcoe_ctlr_flogi_send() -> spin_lock_bh(&fip->ctlr_lock) 2. fcoe_ctlr_recv_work() -> fcoe_ctlr_recv_handler() -> fcoe_ctlr_recv_els() -> fcoe_ctlr_announce() -> spin_lock_bh(&fip->ctlr_lock) 3. fcoe_ctlr_recv_work() -> fcoe_ctlr_recv_handler() -> fcoe_ctlr_recv_els() -> fcoe_ctlr_flogi_retry() -> spin_lock_bh(&fip->ctlr_lock) 4. -> fcoe_xmit() -> fcoe_ctlr_els_send() -> spin_lock_bh(&fip->ctlr_lock) spin_lock_bh() is not enough since fnic_isr_msix_wq_copy() is a hardirq. These flaws were found by an experimental static analysis tool I am developing for irq-related deadlock. The patch fix the potential deadlocks by spin_lock_irqsave() to disable hard irq.
Reviewed-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>
