--- /dev/null
+/*
+ * The implementation of the routines described here is covered by the GPL.
+ * This header file is covered by the following license:
+ */
+
+/*
+ * Copyright (c) 2005 Hewlett-Packard Development Company, L.P.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+/* Almost lock-free LIFO linked lists (linked stacks). */
+#ifndef AO_STACK_H
+#define AO_STACK_H
+
+#include "atomic_ops.h"
+
+#if !defined(AO_HAVE_compare_double_and_swap_double) \
+ && !defined(AO_HAVE_compare_double_and_swap) \
+ && defined(AO_HAVE_compare_and_swap)
+# define AO_USE_ALMOST_LOCK_FREE
+#else
+ /* If we have no compare-and-swap operation defined, we assume */
+ /* that we will actually be using CAS emulation. If we do that, */
+ /* it's cheaper to use the version-based implementation. */
+# define AO_STACK_IS_LOCK_FREE
+#endif
+
+/*
+ * These are not guaranteed to be completely lock-free.
+ * List insertion may spin under extremely unlikely conditions.
+ * It cannot deadlock due to recursive reentry unless AO_list_remove
+ * is called while at least AO_BL_SIZE activations of
+ * AO_list_remove are currently active in the same thread, i.e.
+ * we must have at least AO_BL_SIZE recursive signal handler
+ * invocations.
+ *
+ * All operations take an AO_list_aux argument. It is safe to
+ * share a single AO_list_aux structure among all lists, but that
+ * may increase contention. Any given list must always be accessed
+ * with the same AO_list_aux structure.
+ *
+ * We make some machine-dependent assumptions:
+ * - We have a compare-and-swap operation.
+ * - At least _AO_N_BITS low order bits in pointers are
+ * zero and normally unused.
+ * - size_t and pointers have the same size.
+ *
+ * We do use a fully lock-free implementation if double-width
+ * compare-and-swap operations are available.
+ */
+
+#ifdef AO_USE_ALMOST_LOCK_FREE
+/* The number of low order pointer bits we can use for a small */
+/* version number. */
+# if defined(__LP64__) || defined(_LP64) || defined(_WIN64)
+ /* WIN64 isn't really supported yet. */
+# define AO_N_BITS 3
+# else
+# define AO_N_BITS 2
+# endif
+
+# define AO_BIT_MASK ((1 << AO_N_BITS) - 1)
+/*
+ * AO_stack_aux should be treated as opaque.
+ * It is fully defined here, so it can be allocated, and to facilitate
+ * debugging.
+ */
+#ifndef AO_BL_SIZE
+# define AO_BL_SIZE 2
+#endif
+
+#if AO_BL_SIZE > (1 << AO_N_BITS)
+# error AO_BL_SIZE too big
+#endif
+
+typedef struct AO__stack_aux {
+ volatile AO_t AO_stack_bl[AO_BL_SIZE];
+} AO_stack_aux;
+
+/* The stack implementation knows only about the location of */
+/* link fields in nodes, and nothing about the rest of the */
+/* stack elements. Link fields hold an AO_t, which is not */
+/* necessarily a real pointer. This converts the AO_t to a */
+/* real (AO_t *) which is either o, or points at the link */
+/* field in the next node. */
+#define AO_REAL_NEXT_PTR(x) (AO_t *)((x) & ~AO_BIT_MASK)
+
+/* The following two routines should not normally be used directly. */
+/* We make them visible here for the rare cases in which it makes sense */
+/* to share the an AO_stack_aux between stacks. */
+void
+AO_stack_push_explicit_aux_release(volatile AO_t *list, AO_t *x,
+ AO_stack_aux *);
+
+AO_t *
+AO_stack_pop_explicit_aux_acquire(volatile AO_t *list, AO_stack_aux *);
+
+/* And now AO_stack_t for the real interface: */
+
+typedef struct AO__stack {
+ volatile AO_t AO_ptr;
+ AO_stack_aux AO_aux;
+} AO_stack_t;
+
+#define AO_STACK_INITIALIZER {0}
+
+AO_INLINE void AO_stack_init(AO_stack_t *list)
+{
+# if AO_BL_SIZE == 2
+ list -> AO_aux.AO_stack_bl[0] = 0;
+ list -> AO_aux.AO_stack_bl[1] = 0;
+# else
+ int i;
+ for (i = 0; i < AO_BL_SIZE; ++i)
+ list -> AO_aux.AO_stack_bl[i] = 0;
+# endif
+ list -> AO_ptr = 0;
+}
+
+/* Convert an AO_stack_t to a pointer to the link field in */
+/* the first element. */
+#define AO_REAL_HEAD_PTR(x) AO_REAL_NEXT_PTR((x).AO_ptr)
+
+#define AO_stack_push_release(l, e) \
+ AO_stack_push_explicit_aux_release(&((l)->AO_ptr), e, &((l)->AO_aux))
+#define AO_HAVE_stack_push_release
+
+#define AO_stack_pop_acquire(l) \
+ AO_stack_pop_explicit_aux_acquire(&((l)->AO_ptr), &((l)->AO_aux))
+#define AO_HAVE_stack_pop_acquire
+
+# else /* Use fully non-blocking data structure, wide CAS */
+
+#ifndef AO_HAVE_double_t
+ /* Can happen if we're using CAS emulation, since we don't want to */
+ /* force that here, in case other atomic_ops clients don't want it. */
+# include "atomic_ops/sysdeps/standard_ao_double_t.h"
+#endif
+
+typedef volatile AO_double_t AO_stack_t;
+/* AO_val1 is version, AO_val2 is pointer. */
+
+#define AO_STACK_INITIALIZER {0}
+
+AO_INLINE void AO_stack_init(AO_stack_t *list)
+{
+ list -> AO_val1 = 0;
+ list -> AO_val2 = 0;
+}
+
+#define AO_REAL_HEAD_PTR(x) (AO_t *)((x).AO_val2)
+#define AO_REAL_NEXT_PTR(x) (AO_t *)(x)
+
+void AO_stack_push_release(AO_stack_t *list, AO_t *new_element);
+#define AO_HAVE_stack_push_release
+AO_t * AO_stack_pop_acquire(AO_stack_t *list);
+#define AO_HAVE_stack_pop_acquire
+
+#endif /* Wide CAS case */
+
+#if defined(AO_HAVE_stack_push_release) && !defined(AO_HAVE_stack_push)
+# define AO_stack_push(l, e) AO_stack_push_release(l, e)
+# define AO_HAVE_stack_push
+#endif
+
+#if defined(AO_HAVE_stack_pop_acquire) && !defined(AO_HAVE_stack_pop)
+# define AO_stack_pop(l) AO_stack_pop_acquire(l)
+# define AO_HAVE_stack_pop
+#endif
+
+#endif /* !AO_STACK_H */
projects / hs-boehmgc.git / blobdiff