[patch] sched: fix latency in random driver

[Ingo Molnar]

the attached patch fixes possibly long scheduling latencies in the
/dev/random driver's rekey_seq_generator() function, by moving the
expensive get_random_bytes() function out from under ip_lock.

has been in the -VP patchset for quite some time.

	Ingo

the attached patch fixes possibly long scheduling latencies in the
/dev/random driver's rekey_seq_generator() function, by moving the
expensive get_random_bytes() function out from under ip_lock.

has been in the -VP patchset for quite some time.

Signed-off-by: Ingo Molnar <mingo@xxxxxxx>

--- linux/drivers/char/random.c.orig	
+++ linux/drivers/char/random.c	
@@ -2220,17 +2220,18 @@ static unsigned int ip_cnt;
 
 static void rekey_seq_generator(void *private_)
 {
-	struct keydata *keyptr;
+	struct keydata *keyptr, tmp;
 	struct timeval 	tv;
 
 	do_gettimeofday(&tv);
+	get_random_bytes(tmp.secret, sizeof(tmp.secret));
 
 	spin_lock_bh(&ip_lock);
 	keyptr = &ip_keydata[ip_cnt&1];
 
 	keyptr = &ip_keydata[1^(ip_cnt&1)];
 	keyptr->rekey_time = tv.tv_sec;
-	get_random_bytes(keyptr->secret, sizeof(keyptr->secret));
+	memcpy(keyptr->secret, tmp.secret, sizeof(keyptr->secret));
 	keyptr->count = (ip_cnt&COUNT_MASK)<<HASH_BITS;
 	mb();
 	ip_cnt++;