[PATCH] rcu: keep rcu callback event counter

This makes call_rcu() keep track of how many events there are on the RCU
list, and cause a reschedule event when the list gets too long.

This helps keep RCU event lists down.

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

2 files changed, 12 insertions, 0 deletions

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 4e65eb44adfd..70191a5a148f 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -94,6 +94,7 @@ struct rcu_data {
         long            batch;           /* Batch # for current RCU batch */
         struct rcu_head *nxtlist;
         struct rcu_head **nxttail;
+        long            count; /* # of queued items */
         struct rcu_head *curlist;
         struct rcu_head **curtail;
         struct rcu_head *donelist;
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index dd99415b1551..2559d4b8f23f 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -109,6 +109,10 @@ void fastcall call_rcu(struct rcu_head *head,
         rdp = &__get_cpu_var(rcu_data);
         *rdp->nxttail = head;
         rdp->nxttail = &head->next;
+
+        if (unlikely(++rdp->count > 10000))
+                set_need_resched();
+
         local_irq_restore(flags);
 }
 
@@ -140,6 +144,12 @@ void fastcall call_rcu_bh(struct rcu_head *head,
         rdp = &__get_cpu_var(rcu_bh_data);
         *rdp->nxttail = head;
         rdp->nxttail = &head->next;
+        rdp->count++;
+/*
+ *  Should we directly call rcu_do_batch() here ?
+ *  if (unlikely(rdp->count > 10000))
+ *      rcu_do_batch(rdp);
+ */
         local_irq_restore(flags);
 }
 
@@ -157,6 +167,7 @@ static void rcu_do_batch(struct rcu_data *rdp)
                 next = rdp->donelist = list->next;
                 list->func(list);
                 list = next;
+                rdp->count--;
                 if (++count >= maxbatch)
                         break;
         }