[PATCH] [1/4] /dev/random: Fix latency in rekeying sequence number

Theodore Ts'o
2004-08-20T04:57:16Z

Based on reports from Ingo's Latency Tracer that the TCP sequence number
rekey code is causing latency problems, I've moved the sequence number
rekey to be done out of a workqueue.

patch-random-1-rekey-workqueue

--- random.c 2004/08/19 22:48:42 1.1
+++ random.c 2004/08/19 22:49:20 1.2
@@ -2246,30 +2246,35 @@
static spinlock_t ip_lock = SPIN_LOCK_UNLOCKED;
static unsigned int ip_cnt;

-static struct keydata *__check_and_rekey(time_t time)
+static void rekey_seq_generator(void *private_)
{
struct keydata *keyptr;
+ struct timeval tv;
+
+ do_gettimeofday(&tv);
+
spin_lock_bh(&ip_lock);
keyptr = &ip_keydata[ip_cnt&1];
- if (!keyptr->rekey_time || (time - keyptr->rekey_time) > REKEY_INTERVAL) {
- keyptr = &ip_keydata[1^(ip_cnt&1)];
- keyptr->rekey_time = time;
- get_random_bytes(keyptr->secret, sizeof(keyptr->secret));
- keyptr->count = (ip_cnt&COUNT_MASK)<<HASH_BITS;
- mb();
- ip_cnt++;
- }
+
+ keyptr = &ip_keydata[1^(ip_cnt&1)];
+ keyptr->rekey_time = tv.tv_sec;
+ get_random_bytes(keyptr->secret, sizeof(keyptr->secret));
+ keyptr->count = (ip_cnt&COUNT_MASK)<<HASH_BITS;
+ mb();
+ ip_cnt++;
+
spin_unlock_bh(&ip_lock);
- return keyptr;
}

+static DECLARE_WORK(rekey_work, rekey_seq_generator, NULL);
+
static inline struct keydata *check_and_rekey(time_t time)
{
struct keydata *keyptr = &ip_keydata[ip_cnt&1];

rmb();
if (!keyptr->rekey_time || (time - keyptr->rekey_time) > REKEY_INTERVAL) {
- keyptr = __check_and_rekey(time);
+ schedule_work(&rekey_work);
}

return keyptr;