[src/trunk]: src/sys/dev/usb simplify the locking in urtwn_start

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

details:   https://anonhg.NetBSD.org/src/rev/6899d29ec287
branches:  trunk
changeset: 784214:6899d29ec287
user:      jmcneill <jmcneill%NetBSD.org@localhost>
date:      Tue Jan 22 12:04:58 2013 +0000

description:
simplify the locking in urtwn_start

diffstat:

 sys/dev/usb/if_urtwn.c |  25 ++++++++++++-------------
 1 files changed, 12 insertions(+), 13 deletions(-)

diffs (67 lines):

diff -r 4576f3aebf7a -r 6899d29ec287 sys/dev/usb/if_urtwn.c
--- a/sys/dev/usb/if_urtwn.c    Tue Jan 22 11:58:39 2013 +0000
+++ b/sys/dev/usb/if_urtwn.c    Tue Jan 22 12:04:58 2013 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: if_urtwn.c,v 1.16 2013/01/21 23:42:45 jmcneill Exp $   */
+/*     $NetBSD: if_urtwn.c,v 1.17 2013/01/22 12:04:58 jmcneill Exp $   */
 /*     $OpenBSD: if_urtwn.c,v 1.20 2011/11/26 06:39:33 ckuethe Exp $   */
 
 /*-
@@ -22,7 +22,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: if_urtwn.c,v 1.16 2013/01/21 23:42:45 jmcneill Exp $");
+__KERNEL_RCSID(0, "$NetBSD: if_urtwn.c,v 1.17 2013/01/22 12:04:58 jmcneill Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_inet.h"
@@ -2331,22 +2331,22 @@
        data = NULL;
        for (;;) {
                mutex_enter(&sc->sc_tx_mtx);
-               if (data == NULL) {
+               if (data == NULL && !TAILQ_EMPTY(&sc->tx_free_list)) {
                        data = TAILQ_FIRST(&sc->tx_free_list);
-                       if (data == NULL) {
-                               mutex_exit(&sc->sc_tx_mtx);
-                               ifp->if_flags |= IFF_OACTIVE;
-                               DPRINTFN(DBG_TX, ("%s: empty tx_free_list\n",
-                                            device_xname(sc->sc_dev)));
-                               return;
-                       }
                        TAILQ_REMOVE(&sc->tx_free_list, data, next);
                }
+               mutex_exit(&sc->sc_tx_mtx);
+
+               if (data == NULL) {
+                       ifp->if_flags |= IFF_OACTIVE;
+                       DPRINTFN(DBG_TX, ("%s: empty tx_free_list\n",
+                                    device_xname(sc->sc_dev)));
+                       return;
+               }
 
                /* Send pending management frames first. */
                IF_DEQUEUE(&ic->ic_mgtq, m);
                if (m != NULL) {
-                       mutex_exit(&sc->sc_tx_mtx);
                        ni = (void *)m->m_pkthdr.rcvif;
                        m->m_pkthdr.rcvif = NULL;
                        goto sendit;
@@ -2359,8 +2359,6 @@
                if (m == NULL)
                        break;
 
-               mutex_exit(&sc->sc_tx_mtx);
-
                if (m->m_len < (int)sizeof(*eh) &&
                    (m = m_pullup(m, sizeof(*eh))) == NULL) {
                        ifp->if_oerrors++;
@@ -2398,6 +2396,7 @@
        }
 
        /* Return the Tx buffer to the free list */
+       mutex_enter(&sc->sc_tx_mtx);
        TAILQ_INSERT_TAIL(&sc->tx_free_list, data, next);
        mutex_exit(&sc->sc_tx_mtx);
 }