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   1 From f10f582d28220f50099d3f561116256267821429 Mon Sep 17 00:00:00 2001
   2 From: Mike Christie <michael.christie@oracle.com>
   3 Date: Tue, 8 Feb 2022 12:54:48 -0600
   4 Subject: scsi: qedi: Fix ABBA deadlock in qedi_process_tmf_resp() and qedi_process_cmd_cleanup_resp()
   5
   6 From: Mike Christie <michael.christie@oracle.com>
   7
   8 commit f10f582d28220f50099d3f561116256267821429 upstream.
   9
  10 This fixes a deadlock added with commit b40f3894e39e ("scsi: qedi: Complete
  11 TMF works before disconnect")
  12
  13 Bug description from Jia-Ju Bai:
  14
  15 qedi_process_tmf_resp()
  16   spin_lock(&session->back_lock); --> Line 201 (Lock A)
  17   spin_lock(&qedi_conn->tmf_work_lock); --> Line 230 (Lock B)
  18
  19 qedi_process_cmd_cleanup_resp()
  20   spin_lock_bh(&qedi_conn->tmf_work_lock); --> Line 752 (Lock B)
  21   spin_lock_bh(&conn->session->back_lock); --> Line 784 (Lock A)
  22
  23 When qedi_process_tmf_resp() and qedi_process_cmd_cleanup_resp() are
  24 concurrently executed, the deadlock can occur.
  25
  26 This patch fixes the deadlock by not holding the tmf_work_lock in
  27 qedi_process_cmd_cleanup_resp while holding the back_lock. The
  28 tmf_work_lock is only needed while we remove the tmf_work from the
  29 work_list.
  30
  31 Link: https://lore.kernel.org/r/20220208185448.6206-1-michael.christie@oracle.com
  32 Fixes: b40f3894e39e ("scsi: qedi: Complete TMF works before disconnect")
  33 Cc: Manish Rangankar <mrangankar@marvell.com>
  34 Cc: Nilesh Javali <njavali@marvell.com>
  35 Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
  36 Reported-by: Jia-Ju Bai <baijiaju1990@gmail.com>
  37 Signed-off-by: Mike Christie <michael.christie@oracle.com>
  38 Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
  39 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  40 ---
  41  drivers/scsi/qedi/qedi_fw.c |    6 ++----
  42  1 file changed, 2 insertions(+), 4 deletions(-)
  43
  44 --- a/drivers/scsi/qedi/qedi_fw.c
  45 +++ b/drivers/scsi/qedi/qedi_fw.c
  46 @@ -772,11 +772,10 @@ static void qedi_process_cmd_cleanup_res
  47                         qedi_cmd->list_tmf_work = NULL;
  48                 }
  49         }
  50 +       spin_unlock_bh(&qedi_conn->tmf_work_lock);
  51
  52 -       if (!found) {
  53 -               spin_unlock_bh(&qedi_conn->tmf_work_lock);
  54 +       if (!found)
  55                 goto check_cleanup_reqs;
  56 -       }
  57
  58         QEDI_INFO(&qedi->dbg_ctx, QEDI_LOG_SCSI_TM,
  59                   "TMF work, cqe->tid=0x%x, tmf flags=0x%x, cid=0x%x\n",
  60 @@ -807,7 +806,6 @@ static void qedi_process_cmd_cleanup_res
  61         qedi_cmd->state = CLEANUP_RECV;
  62  unlock:
  63         spin_unlock_bh(&conn->session->back_lock);
  64 -       spin_unlock_bh(&qedi_conn->tmf_work_lock);
  65         wake_up_interruptible(&qedi_conn->wait_queue);
  66         return;
  67