X-Git-Url: https://git.liburcu.org/?a=blobdiff_plain;f=urcu-call-rcu-impl.h;h=6ea7b9a05d74bdfb0c2760d426306d663cb0ade8;hb=refs%2Fheads%2Fstable-0.6;hp=d09adb1bc431a55923d3bbeb3904939f3344e460;hpb=618b25958fec4d76310f0d9c59e42128e73a8719;p=urcu.git

diff --git a/urcu-call-rcu-impl.h b/urcu-call-rcu-impl.h
index d09adb1..6ea7b9a 100644
--- a/urcu-call-rcu-impl.h
+++ b/urcu-call-rcu-impl.h
@@ -64,8 +64,9 @@ CDS_LIST_HEAD(call_rcu_data_list);
 
 static __thread struct call_rcu_data *thread_call_rcu_data;
 
-/* Guard call_rcu thread creation. */
-
+/*
+ * Guard call_rcu thread creation and atfork handlers.
+ */
 static pthread_mutex_t call_rcu_mutex = PTHREAD_MUTEX_INITIALIZER;
 
 /* If a given thread does not have its own call_rcu thread, this is default. */
@@ -204,7 +205,7 @@ static void call_rcu_wake_up(struct call_rcu_data *crdp)
 {
 	/* Write to call_rcu list before reading/writing futex */
 	cmm_smp_mb();
-	if (unlikely(uatomic_read(&crdp->futex) == -1)) {
+	if (caa_unlikely(uatomic_read(&crdp->futex) == -1)) {
 		uatomic_set(&crdp->futex, 0);
 		futex_async(&crdp->futex, FUTEX_WAKE, 1,
 		      NULL, NULL, 0);
@@ -239,6 +240,21 @@ static void *call_rcu_thread(void *arg)
 		cmm_smp_mb();
 	}
 	for (;;) {
+		if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSE) {
+			/*
+			 * Pause requested. Become quiescent: remove
+			 * ourself from all global lists, and don't
+			 * process any callback. The callback lists may
+			 * still be non-empty though.
+			 */
+			rcu_unregister_thread();
+			cmm_smp_mb__before_uatomic_or();
+			uatomic_or(&crdp->flags, URCU_CALL_RCU_PAUSED);
+			while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSE) != 0)
+				poll(NULL, 0, 1);
+			rcu_register_thread();
+		}
+
 		if (&crdp->cbs.head != _CMM_LOAD_SHARED(crdp->cbs.tail)) {
 			while ((cbs = _CMM_LOAD_SHARED(crdp->cbs.head)) == NULL)
 				poll(NULL, 0, 1);
@@ -396,6 +412,10 @@ struct call_rcu_data *create_call_rcu_data(unsigned long flags,
  * the caller's responsibility to dispose of the removed structure.
  * Use get_cpu_call_rcu_data() to obtain a pointer to the old structure
  * (prior to NULLing it out, of course).
+ *
+ * The caller must wait for a grace-period to pass between return from
+ * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the
+ * previous call rcu data as argument.
  */
 
 int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp)
@@ -612,6 +632,10 @@ void call_rcu(struct rcu_head *head,
  *
  * We also silently refuse to free NULL pointers.  This simplifies
  * the calling code.
+ *
+ * The caller must wait for a grace-period to pass between return from
+ * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the
+ * previous call rcu data as argument.
  */
 void call_rcu_data_free(struct call_rcu_data *crdp)
 {
@@ -637,8 +661,9 @@ void call_rcu_data_free(struct call_rcu_data *crdp)
 		/* Create default call rcu data if need be */
 		(void) get_default_call_rcu_data();
 		cbs_endprev = (struct cds_wfq_node **)
-			uatomic_xchg(&default_call_rcu_data, cbs_tail);
-		*cbs_endprev = cbs;
+			uatomic_xchg(&default_call_rcu_data->cbs.tail,
+					cbs_tail);
+		_CMM_STORE_SHARED(*cbs_endprev, cbs);
 		uatomic_add(&default_call_rcu_data->qlen,
 			    uatomic_read(&crdp->qlen));
 		wake_call_rcu_thread(default_call_rcu_data);
@@ -669,6 +694,7 @@ void free_all_cpu_call_rcu_data(void)
 			fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n");
 		}
 		warned = 1;
+		return;
 	}
 
 	for (cpu = 0; cpu < maxcpus; cpu++) {
@@ -692,12 +718,25 @@ void free_all_cpu_call_rcu_data(void)
 
 /*
  * Acquire the call_rcu_mutex in order to ensure that the child sees
- * all of the call_rcu() data structures in a consistent state.
+ * all of the call_rcu() data structures in a consistent state. Ensure
+ * that all call_rcu threads are in a quiescent state across fork.
  * Suitable for pthread_atfork() and friends.
  */
 void call_rcu_before_fork(void)
 {
+	struct call_rcu_data *crdp;
+
 	call_rcu_lock(&call_rcu_mutex);
+
+	cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
+		uatomic_or(&crdp->flags, URCU_CALL_RCU_PAUSE);
+		cmm_smp_mb__after_uatomic_or();
+		wake_call_rcu_thread(crdp);
+	}
+	cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
+		while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSED) == 0)
+			poll(NULL, 0, 1);
+	}
 }
 
 /*
@@ -707,6 +746,10 @@ void call_rcu_before_fork(void)
  */
 void call_rcu_after_fork_parent(void)
 {
+	struct call_rcu_data *crdp;
+
+	cds_list_for_each_entry(crdp, &call_rcu_data_list, list)
+		uatomic_and(&crdp->flags, ~URCU_CALL_RCU_PAUSE);
 	call_rcu_unlock(&call_rcu_mutex);
 }
 
@@ -739,7 +782,11 @@ void call_rcu_after_fork_child(void)
 	rcu_set_pointer(&per_cpu_call_rcu_data, NULL);
 	thread_call_rcu_data = NULL;
 
-	/* Dispose of all of the rest of the call_rcu_data structures. */
+	/*
+	 * Dispose of all of the rest of the call_rcu_data structures.
+	 * Leftover call_rcu callbacks will be merged into the new
+	 * default call_rcu thread queue.
+	 */
 	cds_list_for_each_entry_safe(crdp, next, &call_rcu_data_list, list) {
 		if (crdp == default_call_rcu_data)
 			continue;