[BUG] scsi: lpfc: possible ABBCCA deadlock involving three threads

[Jia-Ju Bai]

Hello,

My static analysis tool reports a possible ABBCCA deadlock in the lpfc 
driver in Linux 5.10:

lpfc_els_flush_cmd()
  spin_lock(&pring->ring_lock); --> line 8124 (Lock A)
  lpfc_sli_cancel_iocbs()
    lpfc_sli_release_iocbq()
      spin_lock_irqsave(&phba->hbalock, iflags); --> line 1384 (Lock B)

lpfc_sli_abort_taskmgmt()
  spin_lock_irqsave(&phba->hbalock, iflags); --> line 11812 (Lock B)
  spin_lock(&lpfc_cmd->buf_lock); --> line 11830 (Lock C)

lpfc_abort_handler()
  spin_lock(&lpfc_cmd->buf_lock); --> line 4760 (Lock C)
  spin_lock(&pring_s4->ring_lock); --> line 4777 (Lock A)

When lpfc_els_flush_cmd(), lpfc_sli_abort_taskmgmt() and 
lpfc_abort_handler() are concurrently executed, the deadlock can occur.

I am not quite sure whether this possible deadlock is real and how to 
fix it if it is real.
Any feedback would be appreciated, thanks :)

Reported-by: TOTE Robot <oslab@xxxxxxxxxxxxxxx>


Best wishes,
Jia-Ju Bai