Module Name: src
Committed By: knakahara
Date: Fri Jan 27 05:04:47 UTC 2017
Modified Files:
src/sys/dev/pci: if_wm.c
Log Message:
add comment about txq->txq_lock contentions in wm_nq_transmit().
To generate a diff of this commit:
cvs rdiff -u -r1.469 -r1.470 src/sys/dev/pci/if_wm.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/dev/pci/if_wm.c
diff -u src/sys/dev/pci/if_wm.c:1.469 src/sys/dev/pci/if_wm.c:1.470
--- src/sys/dev/pci/if_wm.c:1.469 Thu Jan 26 10:14:52 2017
+++ src/sys/dev/pci/if_wm.c Fri Jan 27 05:04:47 2017
@@ -1,4 +1,4 @@
-/* $NetBSD: if_wm.c,v 1.469 2017/01/26 10:14:52 knakahara Exp $ */
+/* $NetBSD: if_wm.c,v 1.470 2017/01/27 05:04:47 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 1.469 2017/01/26 10:14:52 knakahara Exp $");
+__KERNEL_RCSID(0, "$NetBSD: if_wm.c,v 1.470 2017/01/27 05:04:47 knakahara Exp $");
#ifdef _KERNEL_OPT
#include "opt_net_mpsafe.h"
@@ -7018,6 +7018,16 @@ wm_nq_transmit(struct ifnet *ifp, struct
if (m->m_flags & M_MCAST)
ifp->if_omcasts++;
+ /*
+ * The situations which this mutex_tryenter() fails at running time
+ * are below two patterns.
+ * (1) contention with interrupt handler(wm_txrxintr_msix())
+ * (2) contention with deferred if_start softint(wm_deferred_start())
+ * In the case of (1), the last packet enqueued to txq->txq_interq is
+ * dequeued by wm_deferred_start(). So, it does not get stuck.
+ * In the case of (2), the last packet enqueued to txq->txq_interq is also
+ * dequeued by wm_deferred_start(). So, it does not get stuck, either.
+ */
if (mutex_tryenter(txq->txq_lock)) {
if (!txq->txq_stopping)
wm_nq_transmit_locked(ifp, txq);
