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Commit beb659bd authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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[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 39c90ece (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: default avatarEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 42a73808

net/ipv4/route.c

+59 −24
Original line number Diff line number Diff line
@@ -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 +562,36 @@ 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;



	for (i = 0; i <= rt_hash_mask; i++) {

		if (process_context && need_resched())

			cond_resched();

		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));



		for (; rth; rth = next) {

			next = rth->u.dst.rt_next;

			rt_free(rth);

		}

	}

}



static void rt_check_expire(void)

{

	static unsigned int rover;

	unsigned int i = rover, goal;
@@ -607,33 +637,33 @@ static void rt_check_expire(struct work_struct *work) 
		spin_unlock_bh(rt_hash_lock_addr(i));

	}

	rover = i;

}



/*

 * rt_worker_func() is run in process context.

 * If a whole flush was scheduled, it is done.

 * Else, we call rt_check_expire() to scan part of the hash table

 */

static void rt_worker_func(struct work_struct *work)

{

	if (ip_rt_flush_expected) {

		ip_rt_flush_expected = 0;

		rt_do_flush(1);

	} else

		rt_check_expire();

	schedule_delayed_work(&expires_work, ip_rt_gc_interval);

}



/* This can run from both BH and non-BH contexts, the latter

 * in the case of a forced flush event.

 */

static void rt_run_flush(unsigned long dummy)

static void rt_run_flush(unsigned long process_context)

{

	int i;

	struct rtable *rth, *next;



	rt_deadline = 0;



	get_random_bytes(&rt_hash_rnd, 4);



	for (i = rt_hash_mask; i >= 0; i--) {

		spin_lock_bh(rt_hash_lock_addr(i));

		rth = rt_hash_table[i].chain;

		if (rth)

			rt_hash_table[i].chain = NULL;

		spin_unlock_bh(rt_hash_lock_addr(i));



		for (; rth; rth = next) {

			next = rth->u.dst.rt_next;

			rt_free(rth);

		}

	}

	rt_do_flush(process_context);

}



static DEFINE_SPINLOCK(rt_flush_lock);
@@ -667,7 +697,7 @@ void rt_cache_flush(int delay) 


	if (delay <= 0) {

		spin_unlock_bh(&rt_flush_lock);

		rt_run_flush(0);

		rt_run_flush(user_mode);

		return;

	}
@@ -678,12 +708,17 @@ void rt_cache_flush(int delay) 
	spin_unlock_bh(&rt_flush_lock);

}



/*

 * We change rt_hash_rnd and ask next rt_worker_func() invocation

 * to perform a flush in process context

 */

static void rt_secret_rebuild(unsigned long dummy)

{

	unsigned long now = jiffies;



	rt_cache_flush(0);

	mod_timer(&rt_secret_timer, now + ip_rt_secret_interval);

	get_random_bytes(&rt_hash_rnd, 4);

	ip_rt_flush_expected = 1;

	cancel_delayed_work(&expires_work);

	schedule_delayed_work(&expires_work, HZ/10);

	mod_timer(&rt_secret_timer, jiffies + ip_rt_secret_interval);

}



/*