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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); - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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