[3.0] a71c7de Make the ban lurker skip busy objects

[Martin Blix Grydeland]

commit a71c7de8a15452368de76c384c7d26c5b775bb79
Author: Martin Blix Grydeland <martin at varnish-software.com>
Date:   Wed Jul 4 13:02:55 2012 +0200

    Make the ban lurker skip busy objects
    
    If the ban lurker finds a busy object, skip the object and defer the
    checking to a later pass.
    
    No test case because it is very timing sensitive (but see the trac bug
    report for a VTC-file that mostly triggers it on the 3.0 branch only)
    
    Fixes: #1162

diff --git a/bin/varnishd/cache_ban.c b/bin/varnishd/cache_ban.c
index bab278d..5c1da57 100644
--- a/bin/varnishd/cache_ban.c
+++ b/bin/varnishd/cache_ban.c
@@ -838,6 +838,18 @@ ban_lurker_work(const struct sess *sp, unsigned pass)
 				continue;
 			}
 			/*
+			 * If the object is busy, we can't touch
+			 * it. Defer it to a later run.
+			 */
+			if (oc->flags & OC_F_BUSY) {
+				oc->flags |= pass;
+				VTAILQ_REMOVE(&b->objcore, oc, ban_list);
+				VTAILQ_INSERT_TAIL(&b->objcore, oc, ban_list);
+				Lck_Unlock(&oh->mtx);
+				Lck_Unlock(&ban_mtx);
+				continue;
+			}
+			/*
 			 * Grab a reference to the OC and we can let go of
 			 * the BAN mutex
 			 */