lkml.org 
[lkml]   [2019]   [Apr]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
SubjectRe: unregister_netdevice: waiting for DEV to become free (2)
From
Date
On 4/15/19 7:36 AM, Tetsuo Handa wrote:
> I traced using debug printk() patch shown below.
>

I find tracepoints (see attached patch) and perf are easier to use to
debug device refcnt problems.

For example, limit the stack you have to deal with via sysctl -w
kernel.perf_event_max_stack=16, and add a filter (e.g., --filter 'name
== "lo"') to limit collection to a specific device.
From 068b1b8362ec5fd1b9dffdbd6e84474ada2eb829 Mon Sep 17 00:00:00 2001
From: David Ahern <dsa@cumulusnetworks.com>
Date: Thu, 11 Feb 2016 02:40:12 -0800
Subject: [PATCH] Add tracepoints to dev_hold and dev_put

Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
---
include/linux/netdevice.h | 6 ++++++
include/trace/events/net.h | 38 ++++++++++++++++++++++++++++++++++++++
net/core/dev.c | 21 +++++++++++++++++++++
3 files changed, 65 insertions(+)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 219f53c30cb3..7ef6fc672dfb 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3193,6 +3193,7 @@ extern int netdev_budget;
/* Called by rtnetlink.c:rtnl_unlock() */
void netdev_run_todo(void);

+#if 0
/**
* dev_put - release reference to device
* @dev: network device
@@ -3214,6 +3215,11 @@ static inline void dev_hold(struct net_device *dev)
{
this_cpu_inc(*dev->pcpu_refcnt);
}
+#else
+void dev_put(struct net_device *dev);
+void dev_hold(struct net_device *dev);
+
+#endif

/* Carrier loss detection, dial on demand. The functions netif_carrier_on
* and _off may be called from IRQ context, but it is caller
diff --git a/include/trace/events/net.h b/include/trace/events/net.h
index 49cc7c3de252..9ed73dfe9d09 100644
--- a/include/trace/events/net.h
+++ b/include/trace/events/net.h
@@ -236,6 +236,44 @@ DEFINE_EVENT(net_dev_rx_verbose_template, netif_rx_ni_entry,
TP_ARGS(skb)
);

+TRACE_EVENT(dev_put,
+
+ TP_PROTO(struct net_device *dev),
+
+ TP_ARGS(dev),
+
+ TP_STRUCT__entry(
+ __string( name, dev->name )
+ __field( int, refcnt )
+ ),
+
+ TP_fast_assign(
+ __assign_str(name, dev->name);
+ __entry->refcnt = netdev_refcnt_read(dev);
+ ),
+
+ TP_printk("dev=%s refcnt %d", __get_str(name), __entry->refcnt)
+);
+
+TRACE_EVENT(dev_hold,
+
+ TP_PROTO(struct net_device *dev),
+
+ TP_ARGS(dev),
+
+ TP_STRUCT__entry(
+ __string( name, dev->name )
+ __field( int, refcnt )
+ ),
+
+ TP_fast_assign(
+ __assign_str(name, dev->name);
+ __entry->refcnt = netdev_refcnt_read(dev);
+ ),
+
+ TP_printk("dev=%s refcnt %d", __get_str(name), __entry->refcnt)
+);
+
#endif /* _TRACE_NET_H */

/* This part must be outside protection */
diff --git a/net/core/dev.c b/net/core/dev.c
index f1284835b8c9..99ac067afd18 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -8117,3 +8117,24 @@ static int __init net_dev_init(void)
}

subsys_initcall(net_dev_init);
+
+
+void dev_put(struct net_device *dev)
+{
+ this_cpu_dec(*dev->pcpu_refcnt);
+ trace_dev_put(dev);
+}
+EXPORT_SYMBOL(dev_put);
+
+/**
+ * dev_hold - get reference to device
+ * @dev: network device
+ *
+ * Hold reference to device to keep it from being freed.
+ */
+void dev_hold(struct net_device *dev)
+{
+ this_cpu_inc(*dev->pcpu_refcnt);
+ trace_dev_hold(dev);
+}
+EXPORT_SYMBOL(dev_hold);
--
2.1.4
\
 
 \ /
  Last update: 2019-04-15 17:37    [W:0.067 / U:5.792 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site