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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 39c90ece75 (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 <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2007-11-19 22:43:37 -08:00 committed by David S. Miller
parent 42a73808ed
commit beb659bd8c
1 changed files with 59 additions and 24 deletions
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83
net/ipv4/route.c
View File

@ -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);
}
/*