From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Thu, 29 Sep 2011 21:14:54 +0000 (-0400)
Subject: Merge branch 'master' into urcu/ht-shrink
X-Git-Tag: v0.7.0~43^2~110
X-Git-Url: http://git.liburcu.org/?a=commitdiff_plain;h=1f689e13ea7e519b1afc001e9c55a7b1b60b599f;hp=a4ce4f122a4e615b6426fa876df38f5c3ea5fb8a;p=userspace-rcu.git

Merge branch 'master' into urcu/ht-shrink
---

diff --git a/urcu-bp.c b/urcu-bp.c
index 2ae3408..4c0ab54 100644
--- a/urcu-bp.c
+++ b/urcu-bp.c
@@ -39,6 +39,7 @@
 #include "urcu/wfqueue.h"
 #include "urcu/map/urcu-bp.h"
 #include "urcu/static/urcu-bp.h"
+#include "urcu-pointer.h"
 
 /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
 #undef _LGPL_SOURCE
diff --git a/urcu-call-rcu-impl.h b/urcu-call-rcu-impl.h
index 3e947af..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)
 {
 }
@@ -321,13 +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");
@@ -335,7 +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]);
 }
 
 /*
@@ -409,7 +426,7 @@ 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;
 }
@@ -441,6 +458,9 @@ 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)
 {
@@ -555,6 +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,
@@ -564,10 +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();
 }
 
 /*
@@ -619,7 +644,10 @@ void call_rcu_data_free(struct call_rcu_data *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);
 }
 
@@ -629,17 +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);
 }
 
 /*
@@ -674,6 +722,10 @@ 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.
@@ -681,6 +733,12 @@ 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);
+	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)
diff --git a/urcu-call-rcu.h b/urcu-call-rcu.h
index e76a844..5ea0c23 100644
--- a/urcu-call-rcu.h
+++ b/urcu-call-rcu.h
@@ -62,16 +62,28 @@ struct rcu_head {
 /*
  * Exported functions
  */
+
+/*
+ * get_cpu_call_rcu_data should be called with RCU read-side lock held.
+ * Callers should be registered RCU read-side threads.
+ */
 struct call_rcu_data *get_cpu_call_rcu_data(int cpu);
 pthread_t get_call_rcu_thread(struct call_rcu_data *crdp);
 struct call_rcu_data *create_call_rcu_data(unsigned long flags,
 					   int cpu_affinity);
 int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp);
 struct call_rcu_data *get_default_call_rcu_data(void);
+/*
+ * get_call_rcu_data should be called from registered RCU read-side
+ * threads.
+ */
 struct call_rcu_data *get_call_rcu_data(void);
 struct call_rcu_data *get_thread_call_rcu_data(void);
 void set_thread_call_rcu_data(struct call_rcu_data *crdp);
 int create_all_cpu_call_rcu_data(unsigned long flags);
+/*
+ * call_rcu should be called from registered RCU read-side threads.
+ */
 void call_rcu(struct rcu_head *head,
 	      void (*func)(struct rcu_head *head));
 void call_rcu_data_free(struct call_rcu_data *crdp);
diff --git a/urcu-defer-impl.h b/urcu-defer-impl.h
index d1ab046..34d99c9 100644
--- a/urcu-defer-impl.h
+++ b/urcu-defer-impl.h
@@ -61,7 +61,9 @@
  * Assumes that (void *)-2L is not used often. Used to encode non-aligned
  * functions and non-aligned data using extra space.
  * We encode the (void *)-2L fct as: -2L, fct, data.
- * We encode the (void *)-2L data as: -2L, fct, data.
+ * We encode the (void *)-2L data as either:
+ *   fct | DQ_FCT_BIT, data (if fct is aligned), or
+ *   -2L, fct, data (if fct is not aligned).
  * Here, DQ_FCT_MARK == ~DQ_FCT_BIT. Required for the test order.
  */
 #define DQ_FCT_BIT		(1 << 0)
@@ -122,6 +124,7 @@ static pthread_mutex_t rcu_defer_mutex = PTHREAD_MUTEX_INITIALIZER;
 static pthread_mutex_t defer_thread_mutex = PTHREAD_MUTEX_INITIALIZER;
 
 static int32_t defer_thread_futex;
+static int32_t defer_thread_stop;
 
 /*
  * Written to only by each individual deferer. Read by both the deferer and
@@ -148,7 +151,6 @@ static void mutex_lock_defer(pthread_mutex_t *mutex)
 			perror("Error in pthread mutex lock");
 			exit(-1);
 		}
-		pthread_testcancel();
 		poll(NULL,0,10);
 	}
 #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
@@ -186,7 +188,13 @@ static unsigned long rcu_defer_num_callbacks(void)
 static void wait_defer(void)
 {
 	uatomic_dec(&defer_thread_futex);
-	cmm_smp_mb();	/* Write futex before read queue */
+	/* Write futex before read queue */
+	/* Write futex before read defer_thread_stop */
+	cmm_smp_mb();
+	if (_CMM_LOAD_SHARED(defer_thread_stop)) {
+		uatomic_set(&defer_thread_futex, 0);
+		pthread_exit(0);
+	}
 	if (rcu_defer_num_callbacks()) {
 		cmm_smp_mb();	/* Read queue before write futex */
 		/* Callbacks are queued, don't wait. */
@@ -316,14 +324,27 @@ void _defer_rcu(void (*fct)(void *p), void *p)
 		assert(head - CMM_LOAD_SHARED(defer_queue.tail) == 0);
 	}
 
-	if (unlikely(defer_queue.last_fct_in != fct)) {
+	/*
+	 * Encode:
+	 * if the function is not changed and the data is aligned and it is
+	 * not the marker:
+	 *	store the data
+	 * otherwise if the function is aligned and its not the marker:
+	 *	store the function with DQ_FCT_BIT
+	 *	store the data
+	 * otherwise:
+	 *	store the marker (DQ_FCT_MARK)
+	 *	store the function
+	 *	store the data
+	 *
+	 * Decode: see the comments before 'struct defer_queue'
+	 *         or the code in rcu_defer_barrier_queue().
+	 */
+	if (unlikely(defer_queue.last_fct_in != fct
+			|| DQ_IS_FCT_BIT(p)
+			|| p == DQ_FCT_MARK)) {
 		defer_queue.last_fct_in = fct;
 		if (unlikely(DQ_IS_FCT_BIT(fct) || fct == DQ_FCT_MARK)) {
-			/*
-			 * If the function to encode is not aligned or the
-			 * marker, write DQ_FCT_MARK followed by the function
-			 * pointer.
-			 */
 			_CMM_STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK],
 				      DQ_FCT_MARK);
 			_CMM_STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK],
@@ -333,17 +354,6 @@ void _defer_rcu(void (*fct)(void *p), void *p)
 			_CMM_STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK],
 				      fct);
 		}
-	} else {
-		if (unlikely(DQ_IS_FCT_BIT(p) || p == DQ_FCT_MARK)) {
-			/*
-			 * If the data to encode is not aligned or the marker,
-			 * write DQ_FCT_MARK followed by the function pointer.
-			 */
-			_CMM_STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK],
-				      DQ_FCT_MARK);
-			_CMM_STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK],
-				      fct);
-		}
 	}
 	_CMM_STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK], p);
 	cmm_smp_wmb();	/* Publish new pointer before head */
@@ -359,7 +369,6 @@ void _defer_rcu(void (*fct)(void *p), void *p)
 void *thr_defer(void *args)
 {
 	for (;;) {
-		pthread_testcancel();
 		/*
 		 * "Be green". Don't wake up the CPU if there is no RCU work
 		 * to perform whatsoever. Aims at saving laptop battery life by
@@ -396,10 +405,17 @@ static void stop_defer_thread(void)
 	int ret;
 	void *tret;
 
-	pthread_cancel(tid_defer);
+	_CMM_STORE_SHARED(defer_thread_stop, 1);
+	/* Store defer_thread_stop before testing futex */
+	cmm_smp_mb();
 	wake_up_defer();
+
 	ret = pthread_join(tid_defer, &tret);
 	assert(!ret);
+
+	CMM_STORE_SHARED(defer_thread_stop, 0);
+	/* defer thread should always exit when futex value is 0 */
+	assert(uatomic_read(&defer_thread_futex) == 0);
 }
 
 int rcu_defer_register_thread(void)
diff --git a/urcu-qsbr.c b/urcu-qsbr.c
index 6b6d3af..5530295 100644
--- a/urcu-qsbr.c
+++ b/urcu-qsbr.c
@@ -39,6 +39,7 @@
 #include "urcu/map/urcu-qsbr.h"
 #define BUILD_QSBR_LIB
 #include "urcu/static/urcu-qsbr.h"
+#include "urcu-pointer.h"
 
 /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
 #undef _LGPL_SOURCE
diff --git a/urcu.c b/urcu.c
index 20bbf36..77f6888 100644
--- a/urcu.c
+++ b/urcu.c
@@ -39,6 +39,7 @@
 #include "urcu/wfqueue.h"
 #include "urcu/map/urcu.h"
 #include "urcu/static/urcu.h"
+#include "urcu-pointer.h"
 
 /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
 #undef _LGPL_SOURCE