scsi: libfc: Avoid invoking response handler twice if ep is already completed

A race condition exists between the response handler getting called because
of exchange_mgr_reset() (which clears out all the active XIDs) and the
response we get via an interrupt.

Sequence of events:

	 rport ba0200: Port timeout, state PLOGI
	 rport ba0200: Port entered PLOGI state from PLOGI state
	 xid 1052: Exchange timer armed : 20000 msecs      xid timer armed here
	 rport ba0200: Received LOGO request while in state PLOGI
	 rport ba0200: Delete port
	 rport ba0200: work event 3
	 rport ba0200: lld callback ev 3
	 bnx2fc: rport_event_hdlr: event = 3, port_id = 0xba0200
	 bnx2fc: ba0200 - rport not created Yet!!
	 /* Here we reset any outstanding exchanges before
	 freeing rport using the exch_mgr_reset() */
	 xid 1052: Exchange timer canceled
	 /* Here we got two responses for one xid */
	 xid 1052: invoking resp(), esb 20000000 state 3
	 xid 1052: invoking resp(), esb 20000000 state 3
	 xid 1052: fc_rport_plogi_resp() : ep->resp_active 2
	 xid 1052: fc_rport_plogi_resp() : ep->resp_active 2

Skip the response if the exchange is already completed.

Link: https://lore.kernel.org/r/20201215194731.2326-1-jhasan@marvell.com
Signed-off-by: Javed Hasan <jhasan@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/libfc/fc_exch.c b/drivers/scsi/libfc/fc_exch.c
index d71afae..8410004 100644 (file)
--- a/drivers/scsi/libfc/fc_exch.c
+++ b/drivers/scsi/libfc/fc_exch.c
@@ -1623,8 +1623,13 @@ static void fc_exch_recv_seq_resp(struct fc_exch_mgr *mp, struct fc_frame *fp)
                rc = fc_exch_done_locked(ep);
                WARN_ON(fc_seq_exch(sp) != ep);
                spin_unlock_bh(&ep->ex_lock);
-               if (!rc)
+               if (!rc) {
                        fc_exch_delete(ep);
+               } else {
+                       FC_EXCH_DBG(ep, "ep is completed already,"
+                                       "hence skip calling the resp\n");
+                       goto skip_resp;
+               }
        }
 
        /*
@@ -1643,6 +1648,7 @@ static void fc_exch_recv_seq_resp(struct fc_exch_mgr *mp, struct fc_frame *fp)
        if (!fc_invoke_resp(ep, sp, fp))
                fc_frame_free(fp);
 
+skip_resp:
        fc_exch_release(ep);
        return;
 rel:
@@ -1899,10 +1905,16 @@ static void fc_exch_reset(struct fc_exch *ep)
 
        fc_exch_hold(ep);
 
-       if (!rc)
+       if (!rc) {
                fc_exch_delete(ep);
+       } else {
+               FC_EXCH_DBG(ep, "ep is completed already,"
+                               "hence skip calling the resp\n");
+               goto skip_resp;
+       }
 
        fc_invoke_resp(ep, sp, ERR_PTR(-FC_EX_CLOSED));
+skip_resp:
        fc_seq_set_resp(sp, NULL, ep->arg);
        fc_exch_release(ep);
 }