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

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.

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/drivers/char/random.c b/drivers/char/random.c
index a162ddd65f1525ff30b2696a5e0f7f8f48327753..27c7c90347efbbc0a0a6d78030914377f20370de 100644 (file)
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -2247,30 +2247,35 @@ static struct keydata {
 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;