[master] c457b96 serialize STV_next

[Nils Goroll]

commit c457b965383087714e3afcce60a763fbec295bb1
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Wed Nov 9 14:55:13 2016 +0100

    serialize STV_next
    
    May be a preliminary solution should phk decide to do this differently.
    
    Fixes #2128

diff --git a/bin/varnishd/storage/stevedore.c b/bin/varnishd/storage/stevedore.c
index ef90263..6ecf8ee 100644
--- a/bin/varnishd/storage/stevedore.c
+++ b/bin/varnishd/storage/stevedore.c
@@ -52,13 +52,16 @@ const struct stevedore *
 STV_next()
 {
 	static struct stevedore *stv;
+	static pthread_mutex_t mtx = PTHREAD_MUTEX_INITIALIZER;
 
+	AZ(pthread_mutex_lock(&mtx));
 	if (!STV__iter(&stv))
 		AN(STV__iter(&stv));
 	if (stv == stv_transient) {
 		stv = NULL;
 		AN(STV__iter(&stv));
 	}
+	AZ(pthread_mutex_unlock(&mtx));
 	AN(stv);
 	return (stv);
 }