On Fri, Nov 16, 2007 at 05:40:27PM +0100, Eric Dumazet wrote:
> Hello David
>
> This patch against net-2.6.25 is another step to get a more resistant ip
> route cache.
>
> Thank you
>
> [PATCH] IPV4 : Move ip route cache flush (secret_rebuild) from softirq to
> workqueue
>
> Every 600 seconds (ip_rt_secret_interval), a softirq flush of the whole
> ip route cache is triggered. On loaded machines, this can starve softirq for
> many seconds and can eventually crash.
>
> This patch moves this flush to a workqueue context, using the worker we
> intoduced in commit 39c90ece7565f5c47110c2fa77409d7a9478bd5b
> (IPV4: Convert rt_check_expire() from softirq processing to workqueue.)
>
> Also, immediate flushes (echo 0 >/proc/sys/net/ipv4/route/flush) are using
> rt_do_flush() helper function, wich take attention to rescheduling.
>
> Next step will be to handle delayed flushes
> ("echo -1 >/proc/sys/net/ipv4/route/flush" or
> "ip route flush cache")
>
> Signed-off-by: Eric Dumazet <[EMAIL PROTECTED]>
>
> net/ipv4/route.c | 89 ++++++++++++++++++++++++++++++++-------------
> 1 file changed, 65 insertions(+), 24 deletions(-)
>
> diff --git a/net/ipv4/route.c b/net/ipv4/route.c
> index 856807c..5d74620 100644
> --- a/net/ipv4/route.c
> +++ b/net/ipv4/route.c
> @@ -133,13 +133,14 @@ static int ip_rt_mtu_expires = 10 * 60 * HZ;
> static int ip_rt_min_pmtu = 512 + 20 + 20;
> static int ip_rt_min_advmss = 256;
> static int ip_rt_secret_interval = 10 * 60 * HZ;
> +static int ip_rt_flush_expected;
> static unsigned long rt_deadline;
>
> #define RTprint(a...) printk(KERN_DEBUG a)
>
> static struct timer_list rt_flush_timer;
> -static void rt_check_expire(struct work_struct *work);
> -static DECLARE_DELAYED_WORK(expires_work, rt_check_expire);
> +static void rt_worker_func(struct work_struct *work);
> +static DECLARE_DELAYED_WORK(expires_work, rt_worker_func);
> static struct timer_list rt_secret_timer;
>
> /*
> @@ -561,7 +562,42 @@ static inline int compare_keys(struct flowi *fl1, struct
> flowi *fl2)
> (fl1->iif ^ fl2->iif)) == 0;
> }
>
> -static void rt_check_expire(struct work_struct *work)
> +/*
> + * Perform a full scan of hash table and free all entries.
> + * Can be called by a softirq or a process.
> + * In the later case, we want to be reschedule if necessary
> + */
> +static void rt_do_flush(int process_context)
> +{
> + unsigned int i;
> + struct rtable *rth, *next;
> + unsigned long fake = 0, *flag_ptr;
> +
> + flag_ptr = process_context ? ¤t_thread_info()->flags : &fake;
> +
> + for (i = 0; i <= rt_hash_mask; i++) {
> + rth = rt_hash_table[i].chain;
> + if (rth) {
> + spin_lock_bh(rt_hash_lock_addr(i));
> + rth = rt_hash_table[i].chain;
> + rt_hash_table[i].chain = NULL;
> + spin_unlock_bh(rt_hash_lock_addr(i));
> + }
> + /*
> + * This is a fast version of :
> + * if (process_context && need_resched())
> + */
> + if (unlikely(test_bit(TIF_NEED_RESCHED, flag_ptr)))
> + cond_resched();
> +
> + for (; rth; rth = next) {
> + next = rth->u.dst.rt_next;
> + rt_free(rth);
> + }
> + }
> +}
Is it ever neccessary to call cond_resched() if rt_hash_table[i].chain
is NULL? If not, the following looks cleaner to my eyes:
for (i = 0; i <= rt_hash_mask; i++) {
rth = rt_hash_table[i].chain;
if (!rth)
continue;
spin_lock_bh(rt_hash_lock_addr(i));
rth = rt_hash_table[i].chain;
rt_hash_table[i].chain = NULL;
spin_unlock_bh(rt_hash_lock_addr(i));
...
--
Horms, California Edition
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