[src/trunk]: src/sys/dev/pci avoid rbuf starvation. when grabbing a recieve ...

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

details:   https://anonhg.NetBSD.org/src/rev/aba210b55e91
branches:  trunk
changeset: 753815:aba210b55e91
user:      mrg <mrg%NetBSD.org@localhost>
date:      Sun Apr 11 02:02:14 2010 +0000

description:
avoid rbuf starvation.  when grabbing a recieve buffer, if a local
4KB buffer isn't available, try to MEXTMALLOC() one.  only if both
of these fail to we abort the recieve operation.

based on a patch from Sverre Froyen <sverre%viewmark.com@localhost>, thanks!

tested by myself, sverre and jeremy reed.

diffstat:

 sys/dev/pci/if_iwn.c |  34 +++++++++++++++++++---------------
 1 files changed, 19 insertions(+), 15 deletions(-)

diffs (62 lines):

diff -r 7773b0b9eff9 -r aba210b55e91 sys/dev/pci/if_iwn.c
--- a/sys/dev/pci/if_iwn.c      Sun Apr 11 01:53:03 2010 +0000
+++ b/sys/dev/pci/if_iwn.c      Sun Apr 11 02:02:14 2010 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: if_iwn.c,v 1.38 2010/04/05 07:20:26 joerg Exp $        */
+/*     $NetBSD: if_iwn.c,v 1.39 2010/04/11 02:02:14 mrg Exp $  */
 /*     $OpenBSD: if_iwn.c,v 1.49 2009/03/29 21:53:52 sthen Exp $       */
 
 /*-
@@ -23,7 +23,7 @@
  * 802.11 network adapters.
  */
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: if_iwn.c,v 1.38 2010/04/05 07:20:26 joerg Exp $");
+__KERNEL_RCSID(0, "$NetBSD: if_iwn.c,v 1.39 2010/04/11 02:02:14 mrg Exp $");
 
 
 #include <sys/param.h>
@@ -1930,8 +1930,8 @@
        }
 
        /*
-        * See comment in if_wpi.c:wpi_rx_intr() about locking
-        * nb_free_entries here.  In short:  it's not required.
+        * Try to grab a local 4KB buffer.  If it fails, try to
+        * MEXTMALLOC() next, and if that fails, give up.
         */
        MGETHDR(m1, M_DONTWAIT, MT_DATA);
        if (m1 == NULL) {
@@ -1939,17 +1939,21 @@
                ifp->if_ierrors++;
                return;
        }
-       if (sc->rxq.nb_free_entries <= 0) {
-               ic->ic_stats.is_rx_nobuf++;
-               ifp->if_ierrors++;
-               m_freem(m1);
-               return;
-       }
-       rbuf = iwn_alloc_rbuf(sc);
-       /* Attach RX buffer to mbuf header. */
-       MEXTADD(m1, rbuf->vaddr, IWN_RBUF_SIZE, 0, iwn_free_rbuf,
-           rbuf);
-       m1->m_flags |= M_EXT_RW;
+       if ((rbuf = iwn_alloc_rbuf(sc)) == NULL) {
+               MEXTMALLOC(m1, IWN_RBUF_SIZE, M_DONTWAIT);
+               if (!(m1->m_flags & M_EXT)) {
+                       ic->ic_stats.is_rx_nobuf++;
+                       ifp->if_ierrors++;
+                       m_freem(m1);
+                       return;
+               }
+       } else {
+               /* Attach RX buffer to mbuf header. */
+               MEXTADD(m1, rbuf->vaddr, IWN_RBUF_SIZE, 0, iwn_free_rbuf,
+                   rbuf);
+               m1->m_flags |= M_EXT_RW;
+       }
+
        bus_dmamap_unload(sc->sc_dmat, data->map);
 
        error = bus_dmamap_load(sc->sc_dmat, data->map, m1->m_ext.ext_buf,