Module Name: src
Committed By: knakahara
Date: Fri Feb 17 11:57:26 UTC 2017
Modified Files:
src/sys/dev/pci: if_wm.c
Log Message:
rxq_ptr must be updated holding rxq_lock consistent with the Rx processing.
In previous implementation, wm_rxeof() temporarily unlock rxq->rxq_lock to
call if_percpuq_enqueue(), and then re-lock rxq->rxq_lock to update
rxq->rxq_ptr. So, if multiple CPUs share the same rxq, there is race e.g.
- CPU A: lock rxq->rxq_lock
- CPU A: Rx processing include increment local variable "i"
- CPU A: unlock rxq->rxq_lock
- CPU A: call if_percpuq_enqueue()
- CPU B: lock rxq->rxq_lock
- CPU B: Rx processing include increment local variable "i"
- CPU B: unlock rxq->rxq_lock
- CPU B: call if_percpuq_enqueue()
- CPU B: lock rxq->rxq_lock
- CPU B: update rxq->rxq_ptr, that is, set CPU B's local "i" to rxq->rxq_ptr
- CPU B: unlock rxq->rxq_lock
- CPU A: lock rxq->rxq_lock
- CPU A: update rxq->rxq_ptr, that is, set CPU A's local "i" to rxq->rxq_ptr
- CPU A: unlock rxq->rxq_lock
To generate a diff of this commit:
cvs rdiff -u -r1.482 -r1.483 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:1.482 src/sys/dev/pci/if_wm.c:1.483
--- src/sys/dev/pci/if_wm.c:1.482 Fri Feb 17 07:21:28 2017
+++ src/sys/dev/pci/if_wm.c Fri Feb 17 11:57:26 2017
@@ -1,4 +1,4 @@
-/* $NetBSD: if_wm.c,v 1.482 2017/02/17 07:21:28 knakahara Exp $ */
+/* $NetBSD: if_wm.c,v 1.483 2017/02/17 11:57:26 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 1.482 2017/02/17 07:21:28 knakahara Exp $");
+__KERNEL_RCSID(0, "$NetBSD: if_wm.c,v 1.483 2017/02/17 11:57:26 knakahara Exp $");
#ifdef _KERNEL_OPT
#include "opt_net_mpsafe.h"
@@ -7799,8 +7799,14 @@ wm_rxeof(struct wm_rxqueue *rxq)
uint8_t rsstype = wm_rxdesc_get_rsstype(rxq, i);
#endif
- if (!wm_rxdesc_dd(rxq, i, status))
+ if (!wm_rxdesc_dd(rxq, i, status)) {
+ /*
+ * Update the receive pointer holding rxq_lock
+ * consistent with increment counter.
+ */
+ rxq->rxq_ptr = i;
break;
+ }
count++;
if (__predict_false(rxq->rxq_discard)) {
@@ -7924,7 +7930,11 @@ wm_rxeof(struct wm_rxqueue *rxq)
/* Set up checksum info for this packet. */
wm_rxdesc_ensure_checksum(rxq, status, errors, m);
-
+ /*
+ * Update the receive pointer holding rxq_lock consistent with
+ * increment counter.
+ */
+ rxq->rxq_ptr = i;
mutex_exit(rxq->rxq_lock);
/* Pass it on. */
@@ -7936,8 +7946,6 @@ wm_rxeof(struct wm_rxqueue *rxq)
break;
}
- /* Update the receive pointer. */
- rxq->rxq_ptr = i;
if (count != 0)
rnd_add_uint32(&sc->rnd_source, count);
