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From: Jason Stubbs <jstubbs@work-at.co.jp>
Organization: Work@ Inc
To: Andrew Morton <akpm@osdl.org>
Subject: Re: PROBLEM: Consistent lock up on >=2.6.8
Date: Thu, 25 Nov 2004 10:03:57 +0900
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On Tuesday 05 October 2004 04:05, Andrew Morton wrote:
> Jason Stubbs <jstubbs@work-at.co.jp> wrote:
> >   [<c0157630>] nr_blockdev_pages+0x10/0x51
> >   [<f8b9c7ea>] update_defense_level+0x16/0x22a [ip_vs]
> >   [<f8b9ca06>] defense_timer_handler+0x8/0x2f [ip_vs]
> >   [<c0123216>] run_timer_softirq+0xd4/0x17d
> >   [<c011f84d>] __do_softirq+0xb9/0xcb
> >   [<c01062ab>] do_softirq+0x4f/0x5e
>
> Yeah, that'll deadlock for sure.   Please try this:

I tried this, as previously noted, and it worked without issue. However,
I just checked the 2.6.9 sources and found that this patch wasn't applied.

Just a heads-up...

Regards,
Jason Stubbs


> update_defense_level() is calling si_meminfo() from timer context.  But
> si_meminfo takes non-irq-safe locks.
>
> Move it all to keventd context.
>
> Signed-off-by: Andrew Morton <akpm@osdl.org>
> ---
>
>  25-akpm/net/ipv4/ipvs/ip_vs_ctl.c |   19 ++++++++-----------
>  1 files changed, 8 insertions(+), 11 deletions(-)
>
> diff -puN net/ipv4/ipvs/ip_vs_ctl.c~ipvs-deadlock-fix
> net/ipv4/ipvs/ip_vs_ctl.c ---
> 25/net/ipv4/ipvs/ip_vs_ctl.c~ipvs-deadlock-fix 2004-10-04
> 11:59:01.138835688 -0700 +++ 25-akpm/net/ipv4/ipvs/ip_vs_ctl.c 2004-10-04
> 12:03:07.790338960 -0700 @@ -26,7 +26,7 @@
>  #include <linux/fs.h>
>  #include <linux/sysctl.h>
>  #include <linux/proc_fs.h>
> -#include <linux/timer.h>
> +#include <linux/workqueue.h>
>  #include <linux/swap.h>
>  #include <linux/proc_fs.h>
>  #include <linux/seq_file.h>
> @@ -89,7 +89,7 @@ int ip_vs_get_debug_level(void)
>  #endif
>
>  /*
> - * update_defense_level is called from timer bh and from sysctl.
> + * update_defense_level is called from keventd and from sysctl.
>   */
>  static void update_defense_level(void)
>  {
> @@ -211,19 +211,19 @@ static void update_defense_level(void)
>  /*
>   * Timer for checking the defense
>   */
> -static struct timer_list defense_timer;
>  #define DEFENSE_TIMER_PERIOD 1*HZ
> +static void defense_work_handler(void *data);
> +static DECLARE_WORK(defense_work, defense_work_handler, NULL);
>
> -static void defense_timer_handler(unsigned long data)
> +static void defense_work_handler(void *data)
>  {
>   update_defense_level();
>   if (atomic_read(&ip_vs_dropentry))
>    ip_vs_random_dropentry();
>
> - mod_timer(&defense_timer, jiffies + DEFENSE_TIMER_PERIOD);
> + schedule_delayed_work(&defense_work, DEFENSE_TIMER_PERIOD);
>  }
>
> -
>  int
>  ip_vs_use_count_inc(void)
>  {
> @@ -2361,10 +2361,7 @@ int ip_vs_control_init(void)
>   ip_vs_new_estimator(&ip_vs_stats);
>
>   /* Hook the defense timer */
> - init_timer(&defense_timer);
> - defense_timer.function = defense_timer_handler;
> - defense_timer.expires = jiffies + DEFENSE_TIMER_PERIOD;
> - add_timer(&defense_timer);
> + schedule_delayed_work(&defense_work, DEFENSE_TIMER_PERIOD);
>
>   LeaveFunction(2);
>   return 0;
> @@ -2375,7 +2372,7 @@ void ip_vs_control_cleanup(void)
>  {
>   EnterFunction(2);
>   ip_vs_trash_cleanup();
> - del_timer_sync(&defense_timer);
> + cancel_delayed_work(&defense_work);
>   ip_vs_kill_estimator(&ip_vs_stats);
>   unregister_sysctl_table(sysctl_header);
>   proc_net_remove("ip_vs_stats");
> _
-
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