2 * Copyright (C) <1999> Erik Walthinsen <omega@cse.ogi.edu>
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Library General Public
6 * License as published by the Free Software Foundation; either
7 * version 2 of the License, or (at your option) any later version.
9 * This library is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * Library General Public License for more details.
14 * You should have received a copy of the GNU Library General Public
15 * License along with this library; if not, write to the
16 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
17 * Boston, MA 02111-1307, USA.
20 #ifndef __GST_TRASH_STACK_H__
21 #define __GST_TRASH_STACK_H__
24 #include "gstmacros.h"
28 typedef struct _GstTrashStack GstTrashStack;
29 typedef struct _GstTrashStackElement GstTrashStackElement;
31 struct _GstTrashStackElement {
32 GstTrashStackElement *next;
35 struct _GstTrashStack {
36 volatile gpointer head;
37 volatile gulong count; /* for the ABA problem */
38 GMutex *lock; /* lock for C fallback */
41 GST_INLINE_FUNC GstTrashStack* gst_trash_stack_new (void);
42 GST_INLINE_FUNC void gst_trash_stack_init (GstTrashStack *stack);
43 GST_INLINE_FUNC void gst_trash_stack_destroy (GstTrashStack *stack);
44 GST_INLINE_FUNC void gst_trash_stack_free (GstTrashStack *stack);
46 GST_INLINE_FUNC void gst_trash_stack_push (GstTrashStack *stack, gpointer mem);
47 GST_INLINE_FUNC gpointer gst_trash_stack_pop (GstTrashStack *stack);
49 #if defined (GST_CAN_INLINE) || defined (__GST_TRASH_STACK_C__)
51 #if defined (__i386__) && defined (__GNUC__) && __GNUC__ >= 2
54 * intel ia32 optimized lockfree implementations
57 gst_trash_stack_init (GstTrashStack *stack)
64 gst_trash_stack_destroy (GstTrashStack *stack)
69 gst_trash_stack_push (GstTrashStack *stack, gpointer mem)
71 __asm__ __volatile__ (
73 " movl %2, (%1); \n\t" /* mem->next == stack->head */
74 " lock; cmpxchg %1, %0; \n\t" /* if head unchanged, move mem into it */
75 " jnz 1b; \n" /* head changed, retry */
83 GST_INLINE_FUNC gpointer
84 gst_trash_stack_pop (GstTrashStack *stack)
86 GstTrashStackElement *head;
88 /* pop is a little more complicated as we need to avoid the so called ABA
89 * problem that arises when a pop and push of the same element happens
90 * right between when we read head->next and try to swing the new pointer
91 * into place. This is usually solved using a counter which makes it highly
92 * inlikely that we manage to grab the wrong head->next value.
94 __asm__ __volatile__ (
95 " testl %%eax, %%eax; \n\t" /* if (head == NULL) return */
98 " movl (%%eax), %%ebx; \n\t" /* take value pointed to by head (head->next) */
99 " movl %%edx, %%ecx; \n\t" /* take counter */
100 " incl %%ecx; \n\t" /* and increment */
101 " lock; cmpxchg8b %1; \n\t" /* if eax:edx == *stack, move ebx:ecx to *stack,
102 * else *stack is moved into eax:edx again... */
103 " jnz 10b; \n\t" /* ... and we retry */
118 * generic implementation
121 gst_trash_stack_init (GstTrashStack *stack)
124 stack->lock = g_mutex_new();
128 gst_trash_stack_destroy (GstTrashStack *stack)
130 g_mutex_free (stack->lock);
134 gst_trash_stack_push (GstTrashStack *stack, gpointer mem)
136 GstTrashStackElement *elem = (GstTrashStackElement *) mem;
138 g_mutex_lock (stack->lock);
139 elem->next = stack->head;
141 g_mutex_unlock (stack->lock);
144 GST_INLINE_FUNC gpointer
145 gst_trash_stack_pop (GstTrashStack *stack)
147 GstTrashStackElement *head;
149 g_mutex_lock (stack->lock);
150 head = (GstTrashStackElement *) stack->head;
152 stack->head = head->next;
153 g_mutex_unlock (stack->lock);
163 GST_INLINE_FUNC GstTrashStack*
164 gst_trash_stack_new (void)
166 GstTrashStack *stack;
168 stack = g_new (GstTrashStack, 1);
169 gst_trash_stack_init (stack);
175 gst_trash_stack_free (GstTrashStack *stack)
177 gst_trash_stack_destroy (stack);
181 #endif /* defined (G_CAN_INLINE) || defined (__GST_TRASH_STACK_C__)*/
185 #endif /* __GST_TRASH_STACK_H__ */