Add gitignore files

[urcu.git] / urcu.c

diff --git a/urcu.c b/urcu.c
index 0e42207e2bcd59d82127dc308def83b85c424798..8381f7b6f61bc892cdf25d671d21ef5b05aae9a5 100644 (file)
--- a/urcu.c
+++ b/urcu.c
@@ -98,8 +98,8 @@ static void force_mb_single_thread(pthread_t tid)
         * Wait for sighandler (and thus mb()) to execute on every thread.
         * BUSY-LOOP.
         */
-       while (sig_done < 1)
-               smp_rmb();      /* ensure we re-read sig-done */
+       while (LOAD_REMOTE(sig_done) < 1)
+               cpu_relax();
        smp_mb();       /* read sig_done before ending the barrier */
 }
 
@@ -113,15 +113,19 @@ static void force_mb_all_threads(void)
        if (!reader_data)
                return;
        sig_done = 0;
-       smp_mb();       /* write sig_done before sending the signals */
+       /*
+        * pthread_kill has a smp_mb(). But beware, we assume it performs
+        * a cache flush on architectures with non-coherent cache.
+        * smp_mb();    write sig_done before sending the signals
+        */
        for (index = reader_data; index < reader_data + num_readers; index++)
                pthread_kill(index->tid, SIGURCU);
        /*
         * Wait for sighandler (and thus mb()) to execute on every thread.
         * BUSY-LOOP.
         */
-       while (sig_done < num_readers)
-               smp_rmb();      /* ensure we re-read sig-done */
+       while (LOAD_REMOTE(sig_done) < num_readers)
+               cpu_relax();
        smp_mb();       /* read sig_done before ending the barrier */
 }
 #endif
@@ -152,13 +156,14 @@ void wait_for_quiescent_state(void)
 
 void synchronize_rcu(void)
 {
+       internal_urcu_lock();
+
        /* All threads should read qparity before accessing data structure
-        * where new ptr points to. */
+        * where new ptr points to. Must be done within internal_urcu_lock
+        * because it iterates on reader threads.*/
        /* Write new ptr before changing the qparity */
        force_mb_all_threads();
 
-       internal_urcu_lock();
-
        switch_next_urcu_qparity();     /* 0 -> 1 */
 
        /*
@@ -167,7 +172,7 @@ void synchronize_rcu(void)
         * waiting forever while new readers are always accessing data (no
         * progress).
         */
-       smp_mb();
+       smp_mc();
 
        /*
         * Wait for previous parity to be empty of readers.
@@ -180,7 +185,7 @@ void synchronize_rcu(void)
         * the writer waiting forever while new readers are always accessing
         * data (no progress).
         */
-       smp_mb();
+       smp_mc();
 
        switch_next_urcu_qparity();     /* 1 -> 0 */
 
@@ -190,20 +195,19 @@ void synchronize_rcu(void)
         * waiting forever while new readers are always accessing data (no
         * progress).
         */
-       smp_mb();
+       smp_mc();
 
        /*
         * Wait for previous parity to be empty of readers.
         */
        wait_for_quiescent_state();     /* Wait readers in parity 1 */
 
-       internal_urcu_unlock();
-
-       /* All threads should finish using the data referred to by old ptr
-        * before decrementing their urcu_active_readers count */
        /* Finish waiting for reader threads before letting the old ptr being
-        * freed. */
+        * freed. Must be done within internal_urcu_lock because it iterates on
+        * reader threads. */
        force_mb_all_threads();
+
+       internal_urcu_unlock();
 }
 
 void urcu_add_reader(pthread_t id)