X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu-call-rcu-impl.h;h=d09adb1bc431a55923d3bbeb3904939f3344e460;hp=b9e57cd60a2ba731a2030cd36c9b9b6c211c416e;hb=1f689e13ea7e519b1afc001e9c55a7b1b60b599f;hpb=bc2433a9853a945a825c244e9ccfe341b73b2ceb

diff --git a/urcu-call-rcu-impl.h b/urcu-call-rcu-impl.h
index b9e57cd..d09adb1 100644
--- a/urcu-call-rcu-impl.h
+++ b/urcu-call-rcu-impl.h
@@ -82,12 +82,20 @@ static struct call_rcu_data *default_call_rcu_data;
 
 /*
  * Pointer to array of pointers to per-CPU call_rcu_data structures
- * and # CPUs.
+ * and # CPUs. per_cpu_call_rcu_data is a RCU-protected pointer to an
+ * array of RCU-protected pointers to call_rcu_data. call_rcu acts as a
+ * RCU read-side and reads per_cpu_call_rcu_data and the per-cpu pointer
+ * without mutex. The call_rcu_mutex protects updates.
  */
 
 static struct call_rcu_data **per_cpu_call_rcu_data;
 static long maxcpus;
 
+static void maxcpus_reset(void)
+{
+	maxcpus = 0;
+}
+
 /* Allocate the array if it has not already been allocated. */
 
 static void alloc_cpu_call_rcu_data(void)
@@ -104,7 +112,7 @@ static void alloc_cpu_call_rcu_data(void)
 	p = malloc(maxcpus * sizeof(*per_cpu_call_rcu_data));
 	if (p != NULL) {
 		memset(p, '\0', maxcpus * sizeof(*per_cpu_call_rcu_data));
-		per_cpu_call_rcu_data = p;
+		rcu_set_pointer(&per_cpu_call_rcu_data, p);
 	} else {
 		if (!warned) {
 			fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n");
@@ -123,6 +131,10 @@ static void alloc_cpu_call_rcu_data(void)
 static struct call_rcu_data **per_cpu_call_rcu_data = NULL;
 static const long maxcpus = -1;
 
+static void maxcpus_reset(void)
+{
+}
+
 static void alloc_cpu_call_rcu_data(void)
 {
 }
@@ -215,6 +227,11 @@ static void *call_rcu_thread(void *arg)
 		exit(-1);
 	}
 
+	/*
+	 * If callbacks take a read-side lock, we need to be registered.
+	 */
+	rcu_register_thread();
+
 	thread_call_rcu_data = crdp;
 	if (!rt) {
 		uatomic_dec(&crdp->futex);
@@ -247,6 +264,7 @@ static void *call_rcu_thread(void *arg)
 		}
 		if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOP)
 			break;
+		rcu_thread_offline();
 		if (!rt) {
 			if (&crdp->cbs.head
 			    == _CMM_LOAD_SHARED(crdp->cbs.tail)) {
@@ -264,6 +282,7 @@ static void *call_rcu_thread(void *arg)
 		} else {
 			poll(NULL, 0, 10);
 		}
+		rcu_thread_online();
 	}
 	if (!rt) {
 		/*
@@ -273,6 +292,7 @@ static void *call_rcu_thread(void *arg)
 		uatomic_set(&crdp->futex, 0);
 	}
 	uatomic_or(&crdp->flags, URCU_CALL_RCU_STOPPED);
+	rcu_unregister_thread();
 	return NULL;
 }
 
@@ -313,13 +333,18 @@ static void call_rcu_data_init(struct call_rcu_data **crdpp,
  * CPU, returning NULL if there is none.  We cannot automatically
  * created it because the platform we are running on might not define
  * sched_getcpu().
+ *
+ * The call to this function and use of the returned call_rcu_data
+ * should be protected by RCU read-side lock.
  */
 
 struct call_rcu_data *get_cpu_call_rcu_data(int cpu)
 {
 	static int warned = 0;
+	struct call_rcu_data **pcpu_crdp;
 
-	if (per_cpu_call_rcu_data == NULL)
+	pcpu_crdp = rcu_dereference(per_cpu_call_rcu_data);
+	if (pcpu_crdp == NULL)
 		return NULL;
 	if (!warned && maxcpus > 0 && (cpu < 0 || maxcpus <= cpu)) {
 		fprintf(stderr, "[error] liburcu: get CPU # out of range\n");
@@ -327,7 +352,7 @@ struct call_rcu_data *get_cpu_call_rcu_data(int cpu)
 	}
 	if (cpu < 0 || maxcpus <= cpu)
 		return NULL;
-	return per_cpu_call_rcu_data[cpu];
+	return rcu_dereference(pcpu_crdp[cpu]);
 }
 
 /*
@@ -375,9 +400,10 @@ struct call_rcu_data *create_call_rcu_data(unsigned long flags,
 
 int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp)
 {
-	int warned = 0;
+	static int warned = 0;
 
 	call_rcu_lock(&call_rcu_mutex);
+	alloc_cpu_call_rcu_data();
 	if (cpu < 0 || maxcpus <= cpu) {
 		if (!warned) {
 			fprintf(stderr, "[error] liburcu: set CPU # out of range\n");
@@ -387,13 +413,21 @@ int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp)
 		errno = EINVAL;
 		return -EINVAL;
 	}
-	alloc_cpu_call_rcu_data();
-	call_rcu_unlock(&call_rcu_mutex);
+
 	if (per_cpu_call_rcu_data == NULL) {
+		call_rcu_unlock(&call_rcu_mutex);
 		errno = ENOMEM;
 		return -ENOMEM;
 	}
-	per_cpu_call_rcu_data[cpu] = crdp;
+
+	if (per_cpu_call_rcu_data[cpu] != NULL && crdp != NULL) {
+		call_rcu_unlock(&call_rcu_mutex);
+		errno = EEXIST;
+		return -EEXIST;
+	}
+
+	rcu_set_pointer(&per_cpu_call_rcu_data[cpu], crdp);
+	call_rcu_unlock(&call_rcu_mutex);
 	return 0;
 }
 
@@ -424,25 +458,23 @@ struct call_rcu_data *get_default_call_rcu_data(void)
  * structure assigned to the CPU on which the thread is running,
  * followed by the default call_rcu_data structure.  If there is not
  * yet a default call_rcu_data structure, one will be created.
+ *
+ * Calls to this function and use of the returned call_rcu_data should
+ * be protected by RCU read-side lock.
  */
 struct call_rcu_data *get_call_rcu_data(void)
 {
-	int curcpu;
-	static int warned = 0;
+	struct call_rcu_data *crd;
 
 	if (thread_call_rcu_data != NULL)
 		return thread_call_rcu_data;
-	if (maxcpus <= 0)
-		return get_default_call_rcu_data();
-	curcpu = sched_getcpu();
-	if (!warned && (curcpu < 0 || maxcpus <= curcpu)) {
-		fprintf(stderr, "[error] liburcu: gcrd CPU # out of range\n");
-		warned = 1;
+
+	if (maxcpus > 0) {
+		crd = get_cpu_call_rcu_data(sched_getcpu());
+		if (crd)
+			return crd;
 	}
-	if (curcpu >= 0 && maxcpus > curcpu &&
-	    per_cpu_call_rcu_data != NULL &&
-	    per_cpu_call_rcu_data[curcpu] != NULL)
-	    	return per_cpu_call_rcu_data[curcpu];
+
 	return get_default_call_rcu_data();
 }
 
@@ -474,7 +506,9 @@ void set_thread_call_rcu_data(struct call_rcu_data *crdp)
 /*
  * Create a separate call_rcu thread for each CPU.  This does not
  * replace a pre-existing call_rcu thread -- use the set_cpu_call_rcu_data()
- * function if you want that behavior.
+ * function if you want that behavior. Should be paired with
+ * free_all_cpu_call_rcu_data() to teardown these call_rcu worker
+ * threads.
  */
 
 int create_all_cpu_call_rcu_data(unsigned long flags)
@@ -508,8 +542,13 @@ int create_all_cpu_call_rcu_data(unsigned long flags)
 		}
 		call_rcu_unlock(&call_rcu_mutex);
 		if ((ret = set_cpu_call_rcu_data(i, crdp)) != 0) {
-			/* FIXME: Leaks crdp for now. */
-			return ret; /* Can happen on race. */
+			call_rcu_data_free(crdp);
+
+			/* it has been created by other thread */
+			if (ret == -EEXIST)
+				continue;
+
+			return ret;
 		}
 	}
 	return 0;
@@ -536,6 +575,8 @@ static void wake_call_rcu_thread(struct call_rcu_data *crdp)
  * need the first invocation of call_rcu() to be fast, make sure
  * to create a call_rcu thread first.  One way to accomplish this is
  * "get_call_rcu_data();", and another is create_all_cpu_call_rcu_data().
+ *
+ * call_rcu must be called by registered RCU read-side threads.
  */
 
 void call_rcu(struct rcu_head *head,
@@ -545,10 +586,13 @@ void call_rcu(struct rcu_head *head,
 
 	cds_wfq_node_init(&head->next);
 	head->func = func;
+	/* Holding rcu read-side lock across use of per-cpu crdp */
+	rcu_read_lock();
 	crdp = get_call_rcu_data();
 	cds_wfq_enqueue(&crdp->cbs, &head->next);
 	uatomic_inc(&crdp->qlen);
 	wake_call_rcu_thread(crdp);
+	rcu_read_unlock();
 }
 
 /*
@@ -590,14 +634,21 @@ void call_rcu_data_free(struct call_rcu_data *crdp)
 		_CMM_STORE_SHARED(crdp->cbs.head, NULL);
 		cbs_tail = (struct cds_wfq_node **)
 			uatomic_xchg(&crdp->cbs.tail, &crdp->cbs.head);
+		/* 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_add(&default_call_rcu_data->qlen,
 			    uatomic_read(&crdp->qlen));
-		cds_list_del(&crdp->list);
-		free(crdp);
+		wake_call_rcu_thread(default_call_rcu_data);
 	}
+
+	call_rcu_lock(&call_rcu_mutex);
+	cds_list_del(&crdp->list);
+	call_rcu_unlock(&call_rcu_mutex);
+
+	free(crdp);
 }
 
 /*
@@ -606,17 +657,37 @@ void call_rcu_data_free(struct call_rcu_data *crdp)
 void free_all_cpu_call_rcu_data(void)
 {
 	int cpu;
-	struct call_rcu_data *crdp;
+	struct call_rcu_data **crdp;
+	static int warned = 0;
 
 	if (maxcpus <= 0)
 		return;
+
+	crdp = malloc(sizeof(*crdp) * maxcpus);
+	if (!crdp) {
+		if (!warned) {
+			fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n");
+		}
+		warned = 1;
+	}
+
 	for (cpu = 0; cpu < maxcpus; cpu++) {
-		crdp = get_cpu_call_rcu_data(cpu);
-		if (crdp == NULL)
+		crdp[cpu] = get_cpu_call_rcu_data(cpu);
+		if (crdp[cpu] == NULL)
 			continue;
 		set_cpu_call_rcu_data(cpu, NULL);
-		call_rcu_data_free(crdp);
 	}
+	/*
+	 * Wait for call_rcu sites acting as RCU readers of the
+	 * call_rcu_data to become quiescent.
+	 */
+	synchronize_rcu();
+	for (cpu = 0; cpu < maxcpus; cpu++) {
+		if (crdp[cpu] == NULL)
+			continue;
+		call_rcu_data_free(crdp[cpu]);
+	}
+	free(crdp);
 }
 
 /*
@@ -646,11 +717,15 @@ void call_rcu_after_fork_parent(void)
  */
 void call_rcu_after_fork_child(void)
 {
-	struct call_rcu_data *crdp;
+	struct call_rcu_data *crdp, *next;
 
 	/* Release the mutex. */
 	call_rcu_unlock(&call_rcu_mutex);
 
+	/* Do nothing when call_rcu() has not been used */
+	if (cds_list_empty(&call_rcu_data_list))
+		return;
+
 	/*
 	 * Allocate a new default call_rcu_data structure in order
 	 * to get a working call_rcu thread to go with it.
@@ -658,13 +733,16 @@ void call_rcu_after_fork_child(void)
 	default_call_rcu_data = NULL;
 	(void)get_default_call_rcu_data();
 
+	/* Cleanup call_rcu_data pointers before use */
+	maxcpus_reset();
+	free(per_cpu_call_rcu_data);
+	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. */
-	while (call_rcu_data_list.next != call_rcu_data_list.prev) {
-		crdp = cds_list_entry(call_rcu_data_list.prev,
-				      struct call_rcu_data, list);
+	cds_list_for_each_entry_safe(crdp, next, &call_rcu_data_list, list) {
 		if (crdp == default_call_rcu_data)
-			crdp = cds_list_entry(crdp->list.prev,
-					      struct call_rcu_data, list);
+			continue;
 		uatomic_set(&crdp->flags, URCU_CALL_RCU_STOPPED);
 		call_rcu_data_free(crdp);
 	}