Fix: high cpu usage in synchronize_rcu with long RCU read-side C.S.

[urcu.git] / urcu-qsbr.c

diff --git a/urcu-qsbr.c b/urcu-qsbr.c
index d6adc5bfaafa9d4d851842bad7d398967b081eec..cd3beff7337da0225a3c55f36b19e9499ec052e9 100644 (file)
--- a/urcu-qsbr.c
+++ b/urcu-qsbr.c
@@ -121,7 +121,7 @@ static void wait_for_readers(struct cds_list_head *input_readers,
                        struct cds_list_head *cur_snap_readers,
                        struct cds_list_head *qsreaders)
 {
-       int wait_loops = 0;
+       unsigned int wait_loops = 0;
        struct rcu_reader *index, *tmp;
 
        /*
@@ -130,7 +130,6 @@ static void wait_for_readers(struct cds_list_head *input_readers,
         * current rcu_gp.ctr value.
         */
        for (;;) {
-               wait_loops++;
                if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
                        uatomic_set(&rcu_gp.futex, -1);
                        /*
@@ -143,6 +142,8 @@ static void wait_for_readers(struct cds_list_head *input_readers,
                        }
                        /* Write futex before read reader_gp */
                        cmm_smp_mb();
+               } else {
+                       wait_loops++;
                }
                cds_list_for_each_entry_safe(index, tmp, input_readers, node) {
                        switch (rcu_reader_state(&index->ctr)) {