* Stephen Hemminger <shemminger@xxxxxxxxxx> wrote:
> Introduce mod_timer_noact() which for example is to replace the calls to
> del_timer()/add_timer() in __nf_ct_refresh_acct(). It works like mod_timer()
> but doesn't activate or modify the timeout of an inactive timer which is the
> behaviour we want in order to be able to use timers as a means of
> synchronization in nf_conntrack.
>
> A later patch will modify __nf_ct_refresh_acct() to use mod_timer_noact()
> which will then save one spin_lock_irqsave() / spin_lock_irqrestore() pair per
> conntrack timer update. This will also get rid of the race we currently have
> without adding more locking in nf_conntrack.
>
> Signed-off-by: Martin Josefsson <gandalf@xxxxxxxxxxxxxx>
>
> ---
> include/linux/timer.h | 8 ++++++--
> kernel/relay.c | 2 +-
> kernel/timer.c | 40 +++++++++++++++++++++++++++++++++++-----
> 3 files changed, 42 insertions(+), 8 deletions(-)
>
> --- a/include/linux/timer.h 2009-02-17 10:55:33.427785986 -0800
> +++ b/include/linux/timer.h 2009-02-17 11:04:10.291844534 -0800
> @@ -25,6 +25,9 @@ struct timer_list {
>
> extern struct tvec_base boot_tvec_bases;
>
> +#define TIMER_ACT 1
> +#define TIMER_NOACT 0
Ugly flaggery.
> -extern int __mod_timer(struct timer_list *timer, unsigned long expires);
> +extern int __mod_timer(struct timer_list *timer, unsigned long expires, int activate);
This is not really acceptable, it slows down every single
add_timer() and mod_timer() call in the kernel with a flag that
has one specific value in all but your case. There's more than
2000 such callsites in the kernel.
Why dont you use something like this instead:
if (del_timer(timer))
add_timer(timer);
?
Ingo
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