[src/trunk]: src/sys/dev/pci remove WM_CORE_LOCK in deferred start routine.

[knakahara <knakahara%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/ec2ff0977bba
branches:  trunk
changeset: 351100:ec2ff0977bba
user:      knakahara <knakahara%NetBSD.org@localhost>
date:      Thu Feb 02 10:29:10 2017 +0000

description:
remove WM_CORE_LOCK in deferred start routine.

It is enough to check each txq's txq_stopping with
mutex_enter(not mutex_tryenter).

reviewed by ozaki-r@n.o.

diffstat:

 sys/dev/pci/if_wm.c |  40 +++++++++++++++++++++-------------------
 1 files changed, 21 insertions(+), 19 deletions(-)

diffs (87 lines):

diff -r c71c6125e40a -r ec2ff0977bba sys/dev/pci/if_wm.c
--- a/sys/dev/pci/if_wm.c       Thu Feb 02 10:05:35 2017 +0000
+++ b/sys/dev/pci/if_wm.c       Thu Feb 02 10:29:10 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: if_wm.c,v 1.475 2017/02/01 08:56:41 msaitoh Exp $      */
+/*     $NetBSD: if_wm.c,v 1.476 2017/02/02 10:29:10 knakahara Exp $    */
 
 /*
  * Copyright (c) 2001, 2002, 2003, 2004 Wasabi Systems, Inc.
@@ -84,7 +84,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: if_wm.c,v 1.475 2017/02/01 08:56:41 msaitoh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: if_wm.c,v 1.476 2017/02/02 10:29:10 knakahara Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_net_mpsafe.h"
@@ -4720,6 +4720,9 @@
 
        KASSERT(WM_CORE_LOCKED(sc));
 
+       /*
+        * must unset stopping flags in ascending order.
+        */
        for(i = 0; i < sc->sc_nqueues; i++) {
                struct wm_txqueue *txq = &sc->sc_queue[i].wmq_txq;
                struct wm_rxqueue *rxq = &sc->sc_queue[i].wmq_rxq;
@@ -4745,6 +4748,9 @@
 
        sc->sc_core_stopping = true;
 
+       /*
+        * must set stopping flags in ascending order.
+        */
        for(i = 0; i < sc->sc_nqueues; i++) {
                struct wm_rxqueue *rxq = &sc->sc_queue[i].wmq_rxq;
                struct wm_txqueue *txq = &sc->sc_queue[i].wmq_txq;
@@ -7334,22 +7340,23 @@
         * Try to transmit on all Tx queues. Passing a txq somehow and
         * transmitting only on the txq may be better.
         */
-restart:
-       WM_CORE_LOCK(sc);
-       if (sc->sc_core_stopping)
-               goto out;
-
        for (; qid < sc->sc_nqueues; qid++) {
                struct wm_txqueue *txq = &sc->sc_queue[qid].wmq_txq;
 
-               if (!mutex_tryenter(txq->txq_lock))
-                       continue;
-
+               /*
+                * We must mutex_enter(txq->txq_lock) instead of
+                * mutex_tryenter(txq->txq_lock) here.
+                * mutex_tryenter(txq->txq_lock) would fail as this txq's
+                * txq_stopping flag is being set. In this case, this device
+                * begin to stop, so we must not start any Tx processing.
+                * However, it may start Tx processing for sc_queue[qid+1]
+                * if we use mutex_tryenter() here.
+                */
+               mutex_enter(txq->txq_lock);
                if (txq->txq_stopping) {
                        mutex_exit(txq->txq_lock);
-                       continue;
-               }
-               WM_CORE_UNLOCK(sc);
+                       return;
+               }
 
                if ((sc->sc_flags & WM_F_NEWQUEUE) != 0) {
                        /* XXX need for ALTQ */
@@ -7363,12 +7370,7 @@
                        wm_transmit_locked(ifp, txq);
                }
                mutex_exit(txq->txq_lock);
-
-               qid++;
-               goto restart;
-       }
-out:
-       WM_CORE_UNLOCK(sc);
+       }
 }
 
 /* Interrupt */