Add rcu_read_ongoing() API to each urcu flavor

[urcu.git] / urcu-qsbr.c

diff --git a/urcu-qsbr.c b/urcu-qsbr.c
index 5b341b5cfd6d97034b08ca5ea6df913a0c8a7736..786a80d6b16b1936dc62b71b43db18850854dd41 100644 (file)
--- a/urcu-qsbr.c
+++ b/urcu-qsbr.c
@@ -43,6 +43,7 @@
 #include "urcu/tls-compat.h"
 
 #include "urcu-die.h"
+#include "urcu-wait.h"
 
 /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
 #undef _LGPL_SOURCE
@@ -78,6 +79,12 @@ DEFINE_URCU_TLS(unsigned int, rcu_rand_yield);
 
 static CDS_LIST_HEAD(registry);
 
+/*
+ * Queue keeping threads awaiting to wait for a grace period. Contains
+ * struct gp_waiters_thread objects.
+ */
+static DEFINE_URCU_WAIT_QUEUE(gp_waiters);
+
 static void mutex_lock(pthread_mutex_t *mutex)
 {
        int ret;
@@ -198,8 +205,10 @@ void synchronize_rcu(void)
        CDS_LIST_HEAD(cur_snap_readers);
        CDS_LIST_HEAD(qsreaders);
        unsigned long was_online;
+       DEFINE_URCU_WAIT_NODE(wait, URCU_WAIT_WAITING);
+       struct urcu_waiters waiters;
 
-       was_online = URCU_TLS(rcu_reader).ctr;
+       was_online = rcu_read_ongoing();
 
        /* All threads should read qparity before accessing data structure
         * where new ptr points to.  In the "then" case, rcu_thread_offline
@@ -214,8 +223,26 @@ void synchronize_rcu(void)
        else
                cmm_smp_mb();
 
+       /*
+        * Add ourself to gp_waiters queue of threads awaiting to wait
+        * for a grace period. Proceed to perform the grace period only
+        * if we are the first thread added into the queue.
+        */
+       if (urcu_wait_add(&gp_waiters, &wait) != 0) {
+               /* Not first in queue: will be awakened by another thread. */
+               urcu_adaptative_busy_wait(&wait);
+               goto gp_end;
+       }
+       /* We won't need to wake ourself up */
+       urcu_wait_set_state(&wait, URCU_WAIT_RUNNING);
+
        mutex_lock(&rcu_gp_lock);
 
+       /*
+        * Move all waiters into our local queue.
+        */
+       urcu_move_waiters(&waiters, &gp_waiters);
+
        if (cds_list_empty(&registry))
                goto out;
 
@@ -271,7 +298,8 @@ void synchronize_rcu(void)
        cds_list_splice(&qsreaders, &registry);
 out:
        mutex_unlock(&rcu_gp_lock);
-
+       urcu_wake_all_waiters(&waiters);
+gp_end:
        /*
         * Finish waiting for reader threads before letting the old ptr being
         * freed.
@@ -286,8 +314,10 @@ void synchronize_rcu(void)
 {
        CDS_LIST_HEAD(qsreaders);
        unsigned long was_online;
+       DEFINE_URCU_WAIT_NODE(wait, URCU_WAIT_WAITING);
+       struct urcu_waiters waiters;
 
-       was_online = URCU_TLS(rcu_reader).ctr;
+       was_online = rcu_read_ongoing();
 
        /*
         * Mark the writer thread offline to make sure we don't wait for
@@ -299,7 +329,26 @@ void synchronize_rcu(void)
        else
                cmm_smp_mb();
 
+       /*
+        * Add ourself to gp_waiters queue of threads awaiting to wait
+        * for a grace period. Proceed to perform the grace period only
+        * if we are the first thread added into the queue.
+        */
+       if (urcu_wait_add(&gp_waiters, &wait) != 0) {
+               /* Not first in queue: will be awakened by another thread. */
+               urcu_adaptative_busy_wait(&wait);
+               goto gp_end;
+       }
+       /* We won't need to wake ourself up */
+       urcu_wait_set_state(&wait, URCU_WAIT_RUNNING);
+
        mutex_lock(&rcu_gp_lock);
+
+       /*
+        * Move all waiters into our local queue.
+        */
+       urcu_move_waiters(&waiters, &gp_waiters);
+
        if (cds_list_empty(&registry))
                goto out;
 
@@ -333,7 +382,8 @@ void synchronize_rcu(void)
        cds_list_splice(&qsreaders, &registry);
 out:
        mutex_unlock(&rcu_gp_lock);
-
+       urcu_wake_all_waiters(&waiters);
+gp_end:
        if (was_online)
                rcu_thread_online();
        else
@@ -355,6 +405,11 @@ void rcu_read_unlock(void)
        _rcu_read_unlock();
 }
 
+int rcu_read_ongoing(void)
+{
+       return _rcu_read_ongoing();
+}
+
 void rcu_quiescent_state(void)
 {
        _rcu_quiescent_state();