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. */
/*
* 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)
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");
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)
{
}
{
/* 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);
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);
* 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");
}
if (cpu < 0 || maxcpus <= cpu)
return NULL;
- return per_cpu_call_rcu_data[cpu];
+ return rcu_dereference(pcpu_crdp[cpu]);
}
/*
* 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)
errno = EINVAL;
return -EINVAL;
}
- 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;
}
* 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)
{
}
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;
* 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,
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();
}
/*
*
* 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)
{
_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_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));
- 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);
}
/*
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);
}
/*
* 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);
+ }
}
/*
*/
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);
}
/* 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.
default_call_rcu_data = NULL;
(void)get_default_call_rcu_data();
- /* Dispose of all of the rest of the call_rcu_data structures. */
+ /* 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.
+ * 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;
projects / userspace-rcu.git / blobdiff