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Date: Mon, 19 Feb 2007 07:13:00 +0100
From: Jarek Poplawski <jarkao2@...pl>
To: Ben Greear <greearb@...delatech.com>
Cc: Stephen Hemminger <shemminger@...ux-foundation.org>,
Francois Romieu <romieu@...zoreil.com>, netdev@...r.kernel.org,
Kyle Lucke <klucke@...ibm.com>,
Raghavendra Koushik <raghavendra.koushik@...erion.com>,
Al Viro <viro@....linux.org.uk>
Subject: [PATCH 1/2] RTNL and flush_scheduled_work deadlocks
On Fri, Feb 16, 2007 at 11:04:02AM -0800, Ben Greear wrote:
> Stephen Hemminger wrote:
> >On Thu, 15 Feb 2007 23:40:32 -0800
> >Ben Greear <greearb@...delatech.com> wrote:
>
> >>Maybe there should be something like an ASSERT_NOT_RTNL() in the
> >>flush_scheduled_work()
> >>method? If it's performance criticial, #ifdef it out if we're not
> >>debugging locks?
> >>
> >
> >You can't safely add a check like that. What if another cpu had acquired
> >RTNL and was unrelated.
>
> I guess there isn't a way to see if *this* thread is the owner of the RTNL
> currently? I think lockdep knows the owner...maybe could query it somehow,
> or just save the owner in the mutex object when debugging is enabled...
Here is my patch proposal to enable such thing
(and to make ASSERT_RTNL simpler btw.).
Signed-off-by: Jarek Poplawski <jarkao2@...pl>
---
include/linux/rtnetlink.h | 13 +++++++++++--
net/core/rtnetlink.c | 29 ++++++++++++++++++++++++++---
2 files changed, 37 insertions(+), 5 deletions(-)
diff -Nurp linux-2.6.20-git13-/include/linux/rtnetlink.h linux-2.6.20-git13/include/linux/rtnetlink.h
--- linux-2.6.20-git13-/include/linux/rtnetlink.h 2007-02-04 19:44:54.000000000 +0100
+++ linux-2.6.20-git13/include/linux/rtnetlink.h 2007-02-18 22:56:36.000000000 +0100
@@ -704,16 +704,25 @@ extern int rtnl_trylock(void);
extern void rtnetlink_init(void);
extern void __rtnl_unlock(void);
+extern int rtnl_assert(void);
#define ASSERT_RTNL() do { \
- if (unlikely(rtnl_trylock())) { \
- rtnl_unlock(); \
+ if (unlikely(!rtnl_assert())) { \
printk(KERN_ERR "RTNL: assertion failed at %s (%d)\n", \
__FILE__, __LINE__); \
dump_stack(); \
} \
} while(0)
+/* Current process shouldn't hold RTNL lock: */
+#define ASSERT_NOT_RTNL() do { \
+ if (unlikely(rtnl_assert())) { \
+ printk(KERN_ERR "NOT_RTNL: assertion failed at %s (%d)\n", \
+ __FILE__, __LINE__); \
+ dump_stack(); \
+ } \
+} while(0)
+
#define BUG_TRAP(x) do { \
if (unlikely(!(x))) { \
printk(KERN_ERR "KERNEL: assertion (%s) failed at %s (%d)\n", \
diff -Nurp linux-2.6.20-git13-/net/core/rtnetlink.c linux-2.6.20-git13/net/core/rtnetlink.c
--- linux-2.6.20-git13-/net/core/rtnetlink.c 2007-02-15 20:07:11.000000000 +0100
+++ linux-2.6.20-git13/net/core/rtnetlink.c 2007-02-18 22:50:13.000000000 +0100
@@ -57,20 +57,33 @@
#endif /* CONFIG_NET_WIRELESS_RTNETLINK */
static DEFINE_MUTEX(rtnl_mutex);
+static struct thread_info *rtnl_owner;
static struct sock *rtnl;
void rtnl_lock(void)
{
+#if !defined(CONFIG_DEBUG_MUTEXES) && !defined(CONFIG_DEBUG_SPINLOCK)
+ WARN_ON(rtnl_owner == current_thread_info());
+#endif
mutex_lock(&rtnl_mutex);
+ rtnl_owner = current_thread_info();
}
void __rtnl_unlock(void)
{
+#if !defined(CONFIG_DEBUG_MUTEXES) && !defined(CONFIG_DEBUG_SPINLOCK)
+ WARN_ON(rtnl_owner != current_thread_info());
+#endif
+ rtnl_owner = NULL;
mutex_unlock(&rtnl_mutex);
}
void rtnl_unlock(void)
{
+#if !defined(CONFIG_DEBUG_MUTEXES) && !defined(CONFIG_DEBUG_SPINLOCK)
+ WARN_ON(rtnl_owner != current_thread_info());
+#endif
+ rtnl_owner = NULL;
mutex_unlock(&rtnl_mutex);
if (rtnl && rtnl->sk_receive_queue.qlen)
rtnl->sk_data_ready(rtnl, 0);
@@ -79,7 +92,16 @@ void rtnl_unlock(void)
int rtnl_trylock(void)
{
- return mutex_trylock(&rtnl_mutex);
+ int ret;
+
+ if ((ret = mutex_trylock(&rtnl_mutex)))
+ rtnl_owner = current_thread_info();
+ return ret;
+}
+
+int rtnl_assert(void)
+{
+ return (rtnl_owner == current_thread_info());
}
int rtattr_parse(struct rtattr *tb[], int maxattr, struct rtattr *rta, int len)
@@ -805,9 +827,9 @@ static void rtnetlink_rcv(struct sock *s
unsigned int qlen = 0;
do {
- mutex_lock(&rtnl_mutex);
+ rtnl_lock();
netlink_run_queue(sk, &qlen, &rtnetlink_rcv_msg);
- mutex_unlock(&rtnl_mutex);
+ __rtnl_unlock();
netdev_run_todo();
} while (qlen);
@@ -893,3 +915,4 @@ EXPORT_SYMBOL(rtnl_unlock);
EXPORT_SYMBOL(rtnl_unicast);
EXPORT_SYMBOL(rtnl_notify);
EXPORT_SYMBOL(rtnl_set_sk_err);
+EXPORT_SYMBOL(rtnl_assert);
-
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