* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the
- * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
- * Boston, MA 02111-1307, USA.
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
*
* Author: Ryan Lortie <desrt@desrt.ca>
*/
+#include "config.h"
+
#include "gbitlock.h"
+#include <glib/gmessages.h>
#include <glib/gatomic.h>
#include <glib/gslist.h>
#include <glib/gthread.h>
+#include <glib/gslice.h>
#include "gthreadprivate.h"
-#include "config.h"
-
-#include "galias.h"
#ifdef G_BIT_LOCK_FORCE_FUTEX_EMULATION
#undef HAVE_FUTEX
#endif
#ifndef HAVE_FUTEX
+static GMutex g_futex_mutex;
static GSList *g_futex_address_list = NULL;
-static GMutex *g_futex_mutex = NULL;
-#endif
-
-void
-_g_futex_thread_init (void) {
-#ifndef HAVE_FUTEX
- g_futex_mutex = g_mutex_new ();
#endif
-}
#ifdef HAVE_FUTEX
/*
* If anyone actually gets bit by this, please file a bug. :)
*/
#include <linux/futex.h>
-#include <syscall.h>
+#include <sys/syscall.h>
#include <unistd.h>
/* < private >
g_futex_wait (const volatile gint *address,
gint value)
{
- syscall (SYS_futex, address, (gsize) FUTEX_WAIT, (gsize) value, NULL);
+ syscall (__NR_futex, address, (gsize) FUTEX_WAIT, (gsize) value, NULL);
}
/* < private >
static void
g_futex_wake (const volatile gint *address)
{
- syscall (SYS_futex, address, (gsize) FUTEX_WAKE, (gsize) 1, NULL);
+ syscall (__NR_futex, address, (gsize) FUTEX_WAKE, (gsize) 1, NULL);
}
#else
{
const volatile gint *address;
gint ref_count;
- GCond *wait_queue;
+ GCond wait_queue;
} WaitAddress;
static WaitAddress *
g_futex_wait (const volatile gint *address,
gint value)
{
- g_mutex_lock (g_futex_mutex);
+ g_mutex_lock (&g_futex_mutex);
if G_LIKELY (g_atomic_int_get (address) == value)
{
WaitAddress *waiter;
{
waiter = g_slice_new (WaitAddress);
waiter->address = address;
- waiter->wait_queue = g_cond_new ();
+ g_cond_init (&waiter->wait_queue);
waiter->ref_count = 0;
g_futex_address_list =
g_slist_prepend (g_futex_address_list, waiter);
}
waiter->ref_count++;
- g_cond_wait (waiter->wait_queue, g_futex_mutex);
+ g_cond_wait (&waiter->wait_queue, &g_futex_mutex);
if (!--waiter->ref_count)
{
g_futex_address_list =
g_slist_remove (g_futex_address_list, waiter);
- g_cond_free (waiter->wait_queue);
+ g_cond_clear (&waiter->wait_queue);
g_slice_free (WaitAddress, waiter);
}
}
- g_mutex_unlock (g_futex_mutex);
+ g_mutex_unlock (&g_futex_mutex);
}
static void
* 2) need to -stay- locked until the end to ensure a wake()
* in another thread doesn't cause 'waiter' to stop existing
*/
- g_mutex_lock (g_futex_mutex);
+ g_mutex_lock (&g_futex_mutex);
if ((waiter = g_futex_find_address (address)))
- g_cond_signal (waiter->wait_queue);
- g_mutex_unlock (g_futex_mutex);
+ g_cond_signal (&waiter->wait_queue);
+ g_mutex_unlock (&g_futex_mutex);
}
#endif
#define CONTENTION_CLASSES 11
static volatile gint g_bit_lock_contended[CONTENTION_CLASSES];
+#if (defined (i386) || defined (__amd64__))
+ #if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)
+ #define USE_ASM_GOTO 1
+ #endif
+#endif
+
/**
* g_bit_lock:
* @address: a pointer to an integer
g_bit_lock (volatile gint *address,
gint lock_bit)
{
+#ifdef USE_ASM_GOTO
+ retry:
+ __asm__ volatile goto ("lock bts %1, (%0)\n"
+ "jc %l[contended]"
+ : /* no output */
+ : "r" (address), "r" (lock_bit)
+ : "cc", "memory"
+ : contended);
+ return;
+
+ contended:
+ {
+ guint mask = 1u << lock_bit;
+ guint v;
+
+ v = g_atomic_int_get (address);
+ if (v & mask)
+ {
+ guint class = ((gsize) address) % G_N_ELEMENTS (g_bit_lock_contended);
+
+ g_atomic_int_add (&g_bit_lock_contended[class], +1);
+ g_futex_wait (address, v);
+ g_atomic_int_add (&g_bit_lock_contended[class], -1);
+ }
+ }
+ goto retry;
+#else
+ guint mask = 1u << lock_bit;
guint v;
retry:
- v = g_atomic_int_get (address);
- if (v & (1u << lock_bit))
+ v = g_atomic_int_or (address, mask);
+ if (v & mask)
/* already locked */
{
guint class = ((gsize) address) % G_N_ELEMENTS (g_bit_lock_contended);
goto retry;
}
-
- if (!g_atomic_int_compare_and_exchange (address, v, v | (1u << lock_bit)))
- goto retry;
+#endif
}
/**
* g_bit_trylock:
* @address: a pointer to an integer
* @lock_bit: a bit value between 0 and 31
- * @returns: %TRUE if the lock was acquired
*
* Sets the indicated @lock_bit in @address, returning %TRUE if
* successful. If the bit is already set, returns %FALSE immediately.
* @address must be atomic in order for this function to work
* reliably.
*
+ * Returns: %TRUE if the lock was acquired
+ *
* Since: 2.24
**/
gboolean
g_bit_trylock (volatile gint *address,
gint lock_bit)
{
- guint v;
+#ifdef USE_ASM_GOTO
+ gboolean result;
- retry:
- v = g_atomic_int_get (address);
- if (v & (1u << lock_bit))
- /* already locked */
- return FALSE;
+ __asm__ volatile ("lock bts %2, (%1)\n"
+ "setnc %%al\n"
+ "movzx %%al, %0"
+ : "=r" (result)
+ : "r" (address), "r" (lock_bit)
+ : "cc", "memory");
- if (!g_atomic_int_compare_and_exchange (address, v, v | (1u << lock_bit)))
- goto retry;
+ return result;
+#else
+ guint mask = 1u << lock_bit;
+ guint v;
- return TRUE;
+ v = g_atomic_int_or (address, mask);
+
+ return ~v & mask;
+#endif
}
/**
g_bit_unlock (volatile gint *address,
gint lock_bit)
{
- guint class = ((gsize) address) % G_N_ELEMENTS (g_bit_lock_contended);
- guint v;
+#ifdef USE_ASM_GOTO
+ asm volatile ("lock btr %1, (%0)"
+ : /* no output */
+ : "r" (address), "r" (lock_bit)
+ : "cc", "memory");
+#else
+ guint mask = 1u << lock_bit;
+
+ g_atomic_int_and (address, ~mask);
+#endif
+
+ {
+ guint class = ((gsize) address) % G_N_ELEMENTS (g_bit_lock_contended);
+
+ if (g_atomic_int_get (&g_bit_lock_contended[class]))
+ g_futex_wake (address);
+ }
+}
+
+
+/* We emulate pointer-sized futex(2) because the kernel API only
+ * supports integers.
+ *
+ * We assume that the 'interesting' part is always the lower order bits.
+ * This assumption holds because pointer bitlocks are restricted to
+ * using the low order bits of the pointer as the lock.
+ *
+ * On 32 bits, there is nothing to do since the pointer size is equal to
+ * the integer size. On little endian the lower-order bits don't move,
+ * so do nothing. Only on 64bit big endian do we need to do a bit of
+ * pointer arithmetic: the low order bits are shifted by 4 bytes. We
+ * have a helper function that always does the right thing here.
+ *
+ * Since we always consider the low-order bits of the integer value, a
+ * simple cast from (gsize) to (guint) always takes care of that.
+ *
+ * After that, pointer-sized futex becomes as simple as:
+ *
+ * g_futex_wait (g_futex_int_address (address), (guint) value);
+ *
+ * and
+ *
+ * g_futex_wake (g_futex_int_address (int_address));
+ */
+static const volatile gint *
+g_futex_int_address (const volatile void *address)
+{
+ const volatile gint *int_address = address;
+
+ /* this implementation makes these (reasonable) assumptions: */
+ G_STATIC_ASSERT (G_BYTE_ORDER == G_LITTLE_ENDIAN ||
+ (G_BYTE_ORDER == G_BIG_ENDIAN &&
+ sizeof (int) == 4 &&
+ (sizeof (gpointer) == 4 || sizeof (gpointer) == 8)));
+
+#if G_BYTE_ORDER == G_BIG_ENDIAN && GLIB_SIZEOF_VOID_P == 8
+ int_address++;
+#endif
+
+ return int_address;
+}
+
+/**
+ * g_pointer_bit_lock:
+ * @address: a pointer to a #gpointer-sized value
+ * @lock_bit: a bit value between 0 and 31
+ *
+ * This is equivalent to g_bit_lock, but working on pointers (or other
+ * pointer-sized values).
+ *
+ * For portability reasons, you may only lock on the bottom 32 bits of
+ * the pointer.
+ *
+ * Since: 2.30
+ **/
+void
+(g_pointer_bit_lock) (volatile void *address,
+ gint lock_bit)
+{
+ g_return_if_fail (lock_bit < 32);
+ {
+#ifdef USE_ASM_GOTO
retry:
- v = g_atomic_int_get (address);
- if (!g_atomic_int_compare_and_exchange (address, v, v & ~(1u << lock_bit)))
+ asm volatile goto ("lock bts %1, (%0)\n"
+ "jc %l[contended]"
+ : /* no output */
+ : "r" (address), "r" ((gsize) lock_bit)
+ : "cc", "memory"
+ : contended);
+ return;
+
+ contended:
+ {
+ volatile gsize *pointer_address = address;
+ gsize mask = 1u << lock_bit;
+ gsize v;
+
+ v = (gsize) g_atomic_pointer_get (pointer_address);
+ if (v & mask)
+ {
+ guint class = ((gsize) address) % G_N_ELEMENTS (g_bit_lock_contended);
+
+ g_atomic_int_add (&g_bit_lock_contended[class], +1);
+ g_futex_wait (g_futex_int_address (address), v);
+ g_atomic_int_add (&g_bit_lock_contended[class], -1);
+ }
+ }
goto retry;
+#else
+ volatile gsize *pointer_address = address;
+ gsize mask = 1u << lock_bit;
+ gsize v;
+
+ retry:
+ v = g_atomic_pointer_or (pointer_address, mask);
+ if (v & mask)
+ /* already locked */
+ {
+ guint class = ((gsize) address) % G_N_ELEMENTS (g_bit_lock_contended);
- if (g_atomic_int_get (&g_bit_lock_contended[class]))
- g_futex_wake (address);
+ g_atomic_int_add (&g_bit_lock_contended[class], +1);
+ g_futex_wait (g_futex_int_address (address), (guint) v);
+ g_atomic_int_add (&g_bit_lock_contended[class], -1);
+
+ goto retry;
+ }
+#endif
+ }
}
-#define __G_BITLOCK_C__
-#include "galiasdef.c"
+/**
+ * g_pointer_bit_trylock:
+ * @address: a pointer to a #gpointer-sized value
+ * @lock_bit: a bit value between 0 and 31
+ *
+ * This is equivalent to g_bit_trylock, but working on pointers (or
+ * other pointer-sized values).
+ *
+ * For portability reasons, you may only lock on the bottom 32 bits of
+ * the pointer.
+ *
+ * Returns: %TRUE if the lock was acquired
+ *
+ * Since: 2.30
+ **/
+gboolean
+(g_pointer_bit_trylock) (volatile void *address,
+ gint lock_bit)
+{
+ g_return_val_if_fail (lock_bit < 32, FALSE);
+
+ {
+#ifdef USE_ASM_GOTO
+ gboolean result;
+
+ asm volatile ("lock bts %2, (%1)\n"
+ "setnc %%al\n"
+ "movzx %%al, %0"
+ : "=r" (result)
+ : "r" (address), "r" ((gsize) lock_bit)
+ : "cc", "memory");
+
+ return result;
+#else
+ volatile gsize *pointer_address = address;
+ gsize mask = 1u << lock_bit;
+ gsize v;
+
+ g_return_val_if_fail (lock_bit < 32, FALSE);
+
+ v = g_atomic_pointer_or (pointer_address, mask);
+
+ return ~v & mask;
+#endif
+ }
+}
+
+/**
+ * g_pointer_bit_unlock:
+ * @address: a pointer to a #gpointer-sized value
+ * @lock_bit: a bit value between 0 and 31
+ *
+ * This is equivalent to g_bit_unlock, but working on pointers (or other
+ * pointer-sized values).
+ *
+ * For portability reasons, you may only lock on the bottom 32 bits of
+ * the pointer.
+ *
+ * Since: 2.30
+ **/
+void
+(g_pointer_bit_unlock) (volatile void *address,
+ gint lock_bit)
+{
+ g_return_if_fail (lock_bit < 32);
+
+ {
+#ifdef USE_ASM_GOTO
+ asm volatile ("lock btr %1, (%0)"
+ : /* no output */
+ : "r" (address), "r" ((gsize) lock_bit)
+ : "cc", "memory");
+#else
+ volatile gsize *pointer_address = address;
+ gsize mask = 1u << lock_bit;
+
+ g_atomic_pointer_and (pointer_address, ~mask);
+#endif
+
+ {
+ guint class = ((gsize) address) % G_N_ELEMENTS (g_bit_lock_contended);
+ if (g_atomic_int_get (&g_bit_lock_contended[class]))
+ g_futex_wake (g_futex_int_address (address));
+ }
+ }
+}
projects / platform / upstream / glib.git / blobdiff