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/*
* mono-wsq.c: work-stealing queue
*
* Authors:
* Gonzalo Paniagua Javier (gonzalo@novell.com)
*
* Copyright (c) 2010 Novell, Inc (http://www.novell.com)
* Copyright 2011 Xamarin, Inc (http://www.xamarin.com)
*/
#include <string.h>
#include <mono/metadata/object.h>
#include <mono/metadata/mono-wsq.h>
#include <mono/utils/mono-semaphore.h>
#include <mono/utils/mono-tls.h>
#include <mono/utils/atomic.h>
#define INITIAL_LENGTH 32
#define WSQ_DEBUG(...)
//#define WSQ_DEBUG(...) g_message(__VA_ARGS__)
struct _MonoWSQ {
volatile gint head;
volatile gint tail;
MonoArray *queue;
gint32 mask;
MonoSemType lock;
};
#define NO_KEY ((guint32) -1)
static MonoNativeTlsKey wsq_tlskey;
static gboolean wsq_tlskey_inited = FALSE;
void
mono_wsq_init ()
{
if (wsq_tlskey_inited)
return;
mono_native_tls_alloc (&wsq_tlskey, NULL);
wsq_tlskey_inited = TRUE;
}
void
mono_wsq_cleanup ()
{
if (!wsq_tlskey_inited)
return;
mono_native_tls_free (wsq_tlskey);
wsq_tlskey_inited = FALSE;
}
MonoWSQ *
mono_wsq_create ()
{
MonoWSQ *wsq;
MonoDomain *root;
if (!wsq_tlskey_inited)
return NULL;
wsq = g_new0 (MonoWSQ, 1);
wsq->mask = INITIAL_LENGTH - 1;
MONO_GC_REGISTER_ROOT_SINGLE (wsq->queue);
root = mono_get_root_domain ();
wsq->queue = mono_array_new_cached (root, mono_defaults.object_class, INITIAL_LENGTH);
MONO_SEM_INIT (&wsq->lock, 1);
if (!mono_native_tls_set_value (wsq_tlskey, wsq)) {
mono_wsq_destroy (wsq);
wsq = NULL;
}
return wsq;
}
void
mono_wsq_destroy (MonoWSQ *wsq)
{
if (wsq == NULL || wsq->queue == NULL)
return;
g_assert (mono_wsq_count (wsq) == 0);
MONO_GC_UNREGISTER_ROOT (wsq->queue);
MONO_SEM_DESTROY (&wsq->lock);
memset (wsq, 0, sizeof (MonoWSQ));
if (wsq_tlskey_inited && mono_native_tls_get_value (wsq_tlskey) == wsq)
mono_native_tls_set_value (wsq_tlskey, NULL);
g_free (wsq);
}
gint
mono_wsq_count (MonoWSQ *wsq)
{
if (!wsq)
return 0;
return ((wsq->tail - wsq->head) & wsq->mask);
}
gboolean
mono_wsq_local_push (void *obj)
{
int tail;
int head;
int count;
MonoWSQ *wsq;
if (obj == NULL || !wsq_tlskey_inited)
return FALSE;
wsq = (MonoWSQ *) mono_native_tls_get_value (wsq_tlskey);
if (wsq == NULL) {
WSQ_DEBUG ("local_push: no wsq\n");
return FALSE;
}
tail = wsq->tail;
if (tail < wsq->head + wsq->mask) {
mono_array_setref (wsq->queue, tail & wsq->mask, (MonoObject *) obj);
wsq->tail = tail + 1;
WSQ_DEBUG ("local_push: OK %p %p\n", wsq, obj);
return TRUE;
}
MONO_SEM_WAIT (&wsq->lock);
head = wsq->head;
count = wsq->tail - wsq->head;
if (count >= wsq->mask) {
MonoArray *new_array;
int length;
int i;
length = mono_array_length (wsq->queue);
new_array = mono_array_new_cached (mono_get_root_domain (), mono_defaults.object_class, length * 2);
for (i = 0; i < length; i++)
mono_array_setref (new_array, i, mono_array_get (wsq->queue, MonoObject*, (i + head) & wsq->mask));
mono_gc_bzero (mono_array_addr (wsq->queue, MonoObject *, 0), sizeof (MonoObject*) * length);
wsq->queue = new_array;
wsq->head = 0;
wsq->tail = tail = count;
wsq->mask = (wsq->mask << 1) | 1;
}
mono_array_setref (wsq->queue, tail & wsq->mask, obj);
wsq->tail = tail + 1;
MONO_SEM_POST (&wsq->lock);
WSQ_DEBUG ("local_push: LOCK %p %p\n", wsq, obj);
return TRUE;
}
gboolean
mono_wsq_local_pop (void **ptr)
{
int tail;
gboolean res;
MonoWSQ *wsq;
if (ptr == NULL || !wsq_tlskey_inited)
return FALSE;
wsq = (MonoWSQ *) mono_native_tls_get_value (wsq_tlskey);
if (wsq == NULL) {
WSQ_DEBUG ("local_pop: no wsq\n");
return FALSE;
}
tail = wsq->tail;
if (wsq->head >= tail) {
WSQ_DEBUG ("local_pop: empty\n");
return FALSE;
}
tail--;
InterlockedExchange (&wsq->tail, tail);
if (wsq->head <= tail) {
*ptr = mono_array_get (wsq->queue, void *, tail & wsq->mask);
mono_array_set (wsq->queue, void *, tail & wsq->mask, NULL);
WSQ_DEBUG ("local_pop: GOT ONE %p %p\n", wsq, *ptr);
return TRUE;
}
MONO_SEM_WAIT (&wsq->lock);
if (wsq->head <= tail) {
*ptr = mono_array_get (wsq->queue, void *, tail & wsq->mask);
mono_array_set (wsq->queue, void *, tail & wsq->mask, NULL);
res = TRUE;
} else {
wsq->tail = tail + 1;
res = FALSE;
}
MONO_SEM_POST (&wsq->lock);
WSQ_DEBUG ("local_pop: LOCK %d %p %p\n", res, wsq, *ptr);
return res;
}
void
mono_wsq_try_steal (MonoWSQ *wsq, void **ptr, guint32 ms_timeout)
{
if (wsq == NULL || ptr == NULL || *ptr != NULL || !wsq_tlskey_inited)
return;
if (mono_native_tls_get_value (wsq_tlskey) == wsq)
return;
if (mono_sem_timedwait (&wsq->lock, ms_timeout, FALSE) == 0) {
int head;
head = wsq->head;
InterlockedExchange (&wsq->head, head + 1);
if (head < wsq->tail) {
*ptr = mono_array_get (wsq->queue, void *, head & wsq->mask);
mono_array_set (wsq->queue, void *, head & wsq->mask, NULL);
WSQ_DEBUG ("STEAL %p %p\n", wsq, *ptr);
} else {
wsq->head = head;
}
MONO_SEM_POST (&wsq->lock);
}
}
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