doc/examples: update qsbr example

[urcu.git] / urcu-bp.c

diff --git a/urcu-bp.c b/urcu-bp.c
index 4b3cf01801764c9c132c525876e2cf40ec5895d8..a823659f78d4ce93d82a23b95dc05216feb9c903 100644 (file)
--- a/urcu-bp.c
+++ b/urcu-bp.c
@@ -109,13 +109,7 @@ unsigned int rcu_yield_active;
 DEFINE_URCU_TLS(unsigned int, rcu_rand_yield);
 #endif
 
-/*
- * Global grace period counter.
- * Contains the current RCU_GP_CTR_PHASE.
- * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path.
- * Written to only by writer with mutex taken. Read by both writer and readers.
- */
-long rcu_gp_ctr = RCU_GP_COUNT;
+struct rcu_gp rcu_gp = { .ctr = RCU_GP_COUNT };
 
 /*
  * Pointer to registry elements. Written to only by each individual reader. Read
@@ -164,25 +158,44 @@ static void mutex_unlock(pthread_mutex_t *mutex)
                urcu_die(ret);
 }
 
-static void wait_for_readers(void)
+static void wait_for_readers(struct cds_list_head *input_readers,
+                       struct cds_list_head *cur_snap_readers,
+                       struct cds_list_head *qsreaders)
 {
-       CDS_LIST_HEAD(qsreaders);
        int wait_loops = 0;
        struct rcu_reader *index, *tmp;
 
        /*
         * Wait for each thread URCU_TLS(rcu_reader).ctr to either
         * indicate quiescence (not nested), or observe the current
-        * rcu_gp_ctr value.
+        * rcu_gp.ctr value.
         */
        for (;;) {
                wait_loops++;
-               cds_list_for_each_entry_safe(index, tmp, &registry, node) {
-                       if (!rcu_old_gp_ongoing(&index->ctr))
-                               cds_list_move(&index->node, &qsreaders);
+               cds_list_for_each_entry_safe(index, tmp, input_readers, node) {
+                       switch (rcu_reader_state(&index->ctr)) {
+                       case RCU_READER_ACTIVE_CURRENT:
+                               if (cur_snap_readers) {
+                                       cds_list_move(&index->node,
+                                               cur_snap_readers);
+                                       break;
+                               }
+                               /* Fall-through */
+                       case RCU_READER_INACTIVE:
+                               cds_list_move(&index->node, qsreaders);
+                               break;
+                       case RCU_READER_ACTIVE_OLD:
+                               /*
+                                * Old snapshot. Leaving node in
+                                * input_readers will make us busy-loop
+                                * until the snapshot becomes current or
+                                * the reader becomes inactive.
+                                */
+                               break;
+                       }
                }
 
-               if (cds_list_empty(&registry)) {
+               if (cds_list_empty(input_readers)) {
                        break;
                } else {
                        if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS)
@@ -191,18 +204,18 @@ static void wait_for_readers(void)
                                caa_cpu_relax();
                }
        }
-       /* put back the reader list in the registry */
-       cds_list_splice(&qsreaders, &registry);
 }
 
 void synchronize_rcu(void)
 {
+       CDS_LIST_HEAD(cur_snap_readers);
+       CDS_LIST_HEAD(qsreaders);
        sigset_t newmask, oldmask;
        int ret;
 
-       ret = sigemptyset(&newmask);
+       ret = sigfillset(&newmask);
        assert(!ret);
-       ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask);
+       ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
        assert(!ret);
 
        mutex_lock(&rcu_gp_lock);
@@ -221,7 +234,7 @@ void synchronize_rcu(void)
        /*
         * Wait for readers to observe original parity or be quiescent.
         */
-       wait_for_readers();
+       wait_for_readers(&registry, &cur_snap_readers, &qsreaders);
 
        /*
         * Adding a cmm_smp_mb() which is _not_ formally required, but makes the
@@ -231,7 +244,7 @@ void synchronize_rcu(void)
        cmm_smp_mb();
 
        /* Switch parity: 0 -> 1, 1 -> 0 */
-       CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE);
+       CMM_STORE_SHARED(rcu_gp.ctr, rcu_gp.ctr ^ RCU_GP_CTR_PHASE);
 
        /*
         * Must commit qparity update to memory before waiting for other parity
@@ -250,7 +263,12 @@ void synchronize_rcu(void)
        /*
         * Wait for readers to observe new parity or be quiescent.
         */
-       wait_for_readers();
+       wait_for_readers(&cur_snap_readers, NULL, &qsreaders);
+
+       /*
+        * Put quiescent reader list back into registry.
+        */
+       cds_list_splice(&qsreaders, &registry);
 
        /*
         * Finish waiting for reader threads before letting the old ptr being
@@ -277,6 +295,11 @@ void rcu_read_unlock(void)
        _rcu_read_unlock();
 }
 
+int rcu_read_ongoing(void)
+{
+       return _rcu_read_ongoing();
+}
+
 /*
  * only grow for now.
  */
@@ -362,9 +385,9 @@ void rcu_bp_register(void)
        sigset_t newmask, oldmask;
        int ret;
 
-       ret = sigemptyset(&newmask);
+       ret = sigfillset(&newmask);
        assert(!ret);
-       ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask);
+       ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
        assert(!ret);
 
        /*
@@ -397,9 +420,9 @@ void rcu_bp_before_fork(void)
        sigset_t newmask, oldmask;
        int ret;
 
-       ret = sigemptyset(&newmask);
+       ret = sigfillset(&newmask);
        assert(!ret);
-       ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask);
+       ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
        assert(!ret);
        mutex_lock(&rcu_gp_lock);
        saved_fork_signal_mask = oldmask;