X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu-call-rcu-impl.h;h=6580397b1ee42b04a8e48b5c29a76220ea39b6d0;hp=ae93468d8beb4e9fb9167a4dcc5b462892f3d9a2;hb=390f0a26eb268ad42603a106866bacf6fb4a0649;hpb=53a55535da7db6ac6a2f37107baed9130c049333

diff --git a/urcu-call-rcu-impl.h b/urcu-call-rcu-impl.h
index ae93468..6580397 100644
--- a/urcu-call-rcu-impl.h
+++ b/urcu-call-rcu-impl.h
@@ -21,6 +21,7 @@
  */
 
 #define _GNU_SOURCE
+#define _LGPL_SOURCE
 #include <stdio.h>
 #include <pthread.h>
 #include <signal.h>
@@ -35,16 +36,26 @@
 #include <sched.h>
 
 #include "config.h"
-#include "urcu/wfqueue.h"
+#include "urcu/wfcqueue.h"
 #include "urcu-call-rcu.h"
 #include "urcu-pointer.h"
 #include "urcu/list.h"
 #include "urcu/futex.h"
+#include "urcu/tls-compat.h"
+#include "urcu-die.h"
 
 /* Data structure that identifies a call_rcu thread. */
 
 struct call_rcu_data {
-	struct cds_wfq_queue cbs;
+	/*
+	 * We do not align head on a different cache-line than tail
+	 * mainly because call_rcu callback-invocation threads use
+	 * batching ("splice") to get an entire list of callbacks, which
+	 * effectively empties the queue, and requires to touch the tail
+	 * anyway.
+	 */
+	struct cds_wfcq_tail cbs_tail;
+	struct cds_wfcq_head cbs_head;
 	unsigned long flags;
 	int32_t futex;
 	unsigned long qlen; /* maintained for debugging. */
@@ -58,11 +69,11 @@ struct call_rcu_data {
  * Protected by call_rcu_mutex.
  */
 
-CDS_LIST_HEAD(call_rcu_data_list);
+static CDS_LIST_HEAD(call_rcu_data_list);
 
 /* Link a thread using call_rcu() to its call_rcu thread. */
 
-static __thread struct call_rcu_data *thread_call_rcu_data;
+static DEFINE_URCU_TLS(struct call_rcu_data *, thread_call_rcu_data);
 
 /* Guard call_rcu thread creation. */
 
@@ -82,12 +93,20 @@ 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 +123,7 @@ 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 +142,10 @@ 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)
 {
 }
@@ -138,20 +161,22 @@ static int sched_getcpu(void)
 
 static void call_rcu_lock(pthread_mutex_t *pmp)
 {
-	if (pthread_mutex_lock(pmp) != 0) {
-		perror("pthread_mutex_lock");
-		exit(-1);
-	}
+	int ret;
+
+	ret = pthread_mutex_lock(pmp);
+	if (ret)
+		urcu_die(ret);
 }
 
 /* Release the specified pthread mutex. */
 
 static void call_rcu_unlock(pthread_mutex_t *pmp)
 {
-	if (pthread_mutex_unlock(pmp) != 0) {
-		perror("pthread_mutex_unlock");
-		exit(-1);
-	}
+	int ret;
+
+	ret = pthread_mutex_unlock(pmp);
+	if (ret)
+		urcu_die(ret);
 }
 
 #if HAVE_SCHED_SETAFFINITY
@@ -192,7 +217,7 @@ 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);
@@ -204,58 +229,56 @@ static void call_rcu_wake_up(struct call_rcu_data *crdp)
 static void *call_rcu_thread(void *arg)
 {
 	unsigned long cbcount;
-	struct cds_wfq_node *cbs;
-	struct cds_wfq_node **cbs_tail;
-	struct call_rcu_data *crdp = (struct call_rcu_data *)arg;
-	struct rcu_head *rhp;
+	struct call_rcu_data *crdp = (struct call_rcu_data *) arg;
 	int rt = !!(uatomic_read(&crdp->flags) & URCU_CALL_RCU_RT);
+	int ret;
 
-	if (set_thread_cpu_affinity(crdp) != 0) {
-		perror("pthread_setaffinity_np");
-		exit(-1);
-	}
+	ret = set_thread_cpu_affinity(crdp);
+	if (ret)
+		urcu_die(errno);
 
 	/*
 	 * If callbacks take a read-side lock, we need to be registered.
 	 */
 	rcu_register_thread();
 
-	thread_call_rcu_data = crdp;
+	URCU_TLS(thread_call_rcu_data) = crdp;
 	if (!rt) {
 		uatomic_dec(&crdp->futex);
 		/* Decrement futex before reading call_rcu list */
 		cmm_smp_mb();
 	}
 	for (;;) {
-		if (&crdp->cbs.head != _CMM_LOAD_SHARED(crdp->cbs.tail)) {
-			while ((cbs = _CMM_LOAD_SHARED(crdp->cbs.head)) == NULL)
-				poll(NULL, 0, 1);
-			_CMM_STORE_SHARED(crdp->cbs.head, NULL);
-			cbs_tail = (struct cds_wfq_node **)
-				uatomic_xchg(&crdp->cbs.tail, &crdp->cbs.head);
+		struct cds_wfcq_head cbs_tmp_head;
+		struct cds_wfcq_tail cbs_tmp_tail;
+		struct cds_wfcq_node *cbs, *cbs_tmp_n;
+		enum cds_wfcq_ret splice_ret;
+
+		cds_wfcq_init(&cbs_tmp_head, &cbs_tmp_tail);
+		splice_ret = __cds_wfcq_splice_blocking(&cbs_tmp_head,
+			&cbs_tmp_tail, &crdp->cbs_head, &crdp->cbs_tail);
+		assert(splice_ret != CDS_WFCQ_RET_WOULDBLOCK);
+		assert(splice_ret != CDS_WFCQ_RET_DEST_NON_EMPTY);
+		if (splice_ret != CDS_WFCQ_RET_SRC_EMPTY) {
 			synchronize_rcu();
 			cbcount = 0;
-			do {
-				while (cbs->next == NULL &&
-				       &cbs->next != cbs_tail)
-				       	poll(NULL, 0, 1);
-				if (cbs == &crdp->cbs.dummy) {
-					cbs = cbs->next;
-					continue;
-				}
-				rhp = (struct rcu_head *)cbs;
-				cbs = cbs->next;
+			__cds_wfcq_for_each_blocking_safe(&cbs_tmp_head,
+					&cbs_tmp_tail, cbs, cbs_tmp_n) {
+				struct rcu_head *rhp;
+
+				rhp = caa_container_of(cbs,
+					struct rcu_head, next);
 				rhp->func(rhp);
 				cbcount++;
-			} while (cbs != NULL);
+			}
 			uatomic_sub(&crdp->qlen, cbcount);
 		}
 		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)) {
+			if (cds_wfcq_empty(&crdp->cbs_head,
+					&crdp->cbs_tail)) {
 				call_rcu_wait(crdp);
 				poll(NULL, 0, 10);
 				uatomic_dec(&crdp->futex);
@@ -295,14 +318,13 @@ static void call_rcu_data_init(struct call_rcu_data **crdpp,
 			       int cpu_affinity)
 {
 	struct call_rcu_data *crdp;
+	int ret;
 
 	crdp = malloc(sizeof(*crdp));
-	if (crdp == NULL) {
-		fprintf(stderr, "Out of memory.\n");
-		exit(-1);
-	}
+	if (crdp == NULL)
+		urcu_die(errno);
 	memset(crdp, '\0', sizeof(*crdp));
-	cds_wfq_init(&crdp->cbs);
+	cds_wfcq_init(&crdp->cbs_head, &crdp->cbs_tail);
 	crdp->qlen = 0;
 	crdp->futex = 0;
 	crdp->flags = flags;
@@ -310,10 +332,9 @@ static void call_rcu_data_init(struct call_rcu_data **crdpp,
 	crdp->cpu_affinity = cpu_affinity;
 	cmm_smp_mb();  /* Structure initialized before pointer is planted. */
 	*crdpp = crdp;
-	if (pthread_create(&crdp->tid, NULL, call_rcu_thread, crdp) != 0) {
-		perror("pthread_create");
-		exit(-1);
-	}
+	ret = pthread_create(&crdp->tid, NULL, call_rcu_thread, crdp);
+	if (ret)
+		urcu_die(ret);
 }
 
 /*
@@ -321,13 +342,18 @@ 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");
@@ -335,7 +361,7 @@ 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]);
 }
 
 /*
@@ -379,6 +405,10 @@ 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)
@@ -409,7 +439,7 @@ int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp)
 		return -EEXIST;
 	}
 
-	per_cpu_call_rcu_data[cpu] = crdp;
+	rcu_set_pointer(&per_cpu_call_rcu_data[cpu], crdp);
 	call_rcu_unlock(&call_rcu_mutex);
 	return 0;
 }
@@ -441,13 +471,16 @@ 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)
 {
 	struct call_rcu_data *crd;
 
-	if (thread_call_rcu_data != NULL)
-		return thread_call_rcu_data;
+	if (URCU_TLS(thread_call_rcu_data) != NULL)
+		return URCU_TLS(thread_call_rcu_data);
 
 	if (maxcpus > 0) {
 		crd = get_cpu_call_rcu_data(sched_getcpu());
@@ -464,7 +497,7 @@ struct call_rcu_data *get_call_rcu_data(void)
 
 struct call_rcu_data *get_thread_call_rcu_data(void)
 {
-	return thread_call_rcu_data;
+	return URCU_TLS(thread_call_rcu_data);
 }
 
 /*
@@ -480,7 +513,7 @@ struct call_rcu_data *get_thread_call_rcu_data(void)
 
 void set_thread_call_rcu_data(struct call_rcu_data *crdp)
 {
-	thread_call_rcu_data = crdp;
+	URCU_TLS(thread_call_rcu_data) = crdp;
 }
 
 /*
@@ -522,8 +555,13 @@ 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;
@@ -550,6 +588,8 @@ 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,
@@ -557,12 +597,15 @@ void call_rcu(struct rcu_head *head,
 {
 	struct call_rcu_data *crdp;
 
-	cds_wfq_node_init(&head->next);
+	cds_wfcq_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);
+	cds_wfcq_enqueue(&crdp->cbs_head, &crdp->cbs_tail, &head->next);
 	uatomic_inc(&crdp->qlen);
 	wake_call_rcu_thread(crdp);
+	rcu_read_unlock();
 }
 
 /*
@@ -582,13 +625,17 @@ 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.
+ *
+ * Note: introducing __cds_wfcq_splice_blocking() in this function fixed
+ * a list corruption bug in the 0.7.x series. The equivalent fix
+ * appeared in 0.6.8 for the stable-0.6 branch.
  */
 void call_rcu_data_free(struct call_rcu_data *crdp)
 {
-	struct cds_wfq_node *cbs;
-	struct cds_wfq_node **cbs_tail;
-	struct cds_wfq_node **cbs_endprev;
-
 	if (crdp == NULL || crdp == default_call_rcu_data) {
 		return;
 	}
@@ -598,21 +645,21 @@ void call_rcu_data_free(struct call_rcu_data *crdp)
 		while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0)
 			poll(NULL, 0, 1);
 	}
-	if (&crdp->cbs.head != _CMM_LOAD_SHARED(crdp->cbs.tail)) {
-		while ((cbs = _CMM_LOAD_SHARED(crdp->cbs.head)) == NULL)
-			poll(NULL, 0, 1);
-		_CMM_STORE_SHARED(crdp->cbs.head, NULL);
-		cbs_tail = (struct cds_wfq_node **)
-			uatomic_xchg(&crdp->cbs.tail, &crdp->cbs.head);
-		cbs_endprev = (struct cds_wfq_node **)
-			uatomic_xchg(&default_call_rcu_data, cbs_tail);
-		*cbs_endprev = cbs;
+	if (!cds_wfcq_empty(&crdp->cbs_head, &crdp->cbs_tail)) {
+		/* Create default call rcu data if need be */
+		(void) get_default_call_rcu_data();
+		__cds_wfcq_splice_blocking(&default_call_rcu_data->cbs_head,
+			&default_call_rcu_data->cbs_tail,
+			&crdp->cbs_head, &crdp->cbs_tail);
 		uatomic_add(&default_call_rcu_data->qlen,
 			    uatomic_read(&crdp->qlen));
 		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);
 }
 
@@ -622,17 +669,38 @@ 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;
+		return;
+	}
+
 	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);
 }
 
 /*
@@ -667,6 +735,10 @@ void call_rcu_after_fork_child(void)
 	/* 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.
@@ -674,6 +746,12 @@ 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);
+	URCU_TLS(thread_call_rcu_data) = NULL;
+
 	/* Dispose of all of the rest of the call_rcu_data structures. */
 	cds_list_for_each_entry_safe(crdp, next, &call_rcu_data_list, list) {
 		if (crdp == default_call_rcu_data)