gstreamer/gst/gsttrashstack.h

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/* GStreamer
* Copyright (C) <1999> Erik Walthinsen <omega@cse.ogi.edu>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library 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.
*/
#ifndef __GST_TRASH_STACK_H__
#define __GST_TRASH_STACK_H__
#include <glib.h>
#include "gstmacros.h"
G_BEGIN_DECLS
typedef struct _GstTrashStack GstTrashStack;
typedef struct _GstTrashStackElement GstTrashStackElement;
struct _GstTrashStackElement {
GstTrashStackElement *next;
};
struct _GstTrashStack {
volatile gpointer head;
volatile gulong count; /* for the ABA problem */
GMutex *lock; /* lock for C fallback */
};
GST_INLINE_FUNC GstTrashStack* gst_trash_stack_new (void);
GST_INLINE_FUNC void gst_trash_stack_init (GstTrashStack *stack);
GST_INLINE_FUNC void gst_trash_stack_destroy (GstTrashStack *stack);
GST_INLINE_FUNC void gst_trash_stack_free (GstTrashStack *stack);
GST_INLINE_FUNC void gst_trash_stack_push (GstTrashStack *stack, gpointer mem);
GST_INLINE_FUNC gpointer gst_trash_stack_pop (GstTrashStack *stack);
#if defined (GST_CAN_INLINE) || defined (__GST_TRASH_STACK_C__)
#if defined (__i386__) && defined (__GNUC__) && __GNUC__ >= 2
#ifdef GST_CONFIG_NO_SMP
#define SMP_LOCK ""
#else
#define SMP_LOCK "lock ; "
#endif
/*
* intel ia32 optimized lockfree implementations
*/
GST_INLINE_FUNC void
gst_trash_stack_init (GstTrashStack *stack)
{
stack->head = NULL;
stack->count = 0;
}
GST_INLINE_FUNC void
gst_trash_stack_destroy (GstTrashStack *stack)
{
}
GST_INLINE_FUNC void
gst_trash_stack_push (GstTrashStack *stack, gpointer mem)
{
__asm__ __volatile__ (
"1: \n\t"
" movl %2, (%1); \n\t" /* mem->next == stack->head */
SMP_LOCK "cmpxchg %1, %0; \n\t" /* if head unchanged, move mem into it */
" jnz 1b; \n" /* head changed, retry */
:
: "m" (*stack),
"r" (mem),
"a" (stack->head)
);
}
GST_INLINE_FUNC gpointer
gst_trash_stack_pop (GstTrashStack *stack)
{
GstTrashStackElement *head;
/* pop is a little more complicated as we need to avoid the so called ABA
* problem that arises when a pop and push of the same element happens
* right between when we read head->next and try to swing the new pointer
* into place. This is usually solved using a counter which makes it highly
* inlikely that we manage to grab the wrong head->next value.
*/
__asm__ __volatile__ (
" testl %%eax, %%eax; \n\t" /* if (head == NULL) return */
" jz 20f; \n\t"
"10: \n\t"
" movl (%%eax), %%ebx; \n\t" /* take value pointed to by head (head->next) */
" movl %%edx, %%ecx; \n\t" /* take counter */
" incl %%ecx; \n\t" /* and increment */
SMP_LOCK "cmpxchg8b %1; \n\t" /* if eax:edx == *stack, move ebx:ecx to *stack,
* else *stack is moved into eax:edx again... */
" jnz 10b; \n\t" /* ... and we retry */
"20: \n"
: "=a" (head)
: "m" (*stack),
"a" (stack->head),
"d" (stack->count)
: "ecx", "ebx"
);
return head;
}
#else
/*
* generic implementation
*/
GST_INLINE_FUNC void
gst_trash_stack_init (GstTrashStack *stack)
{
stack->head = NULL;
stack->lock = g_mutex_new();
}
GST_INLINE_FUNC void
gst_trash_stack_destroy (GstTrashStack *stack)
{
g_mutex_free (stack->lock);
}
GST_INLINE_FUNC void
gst_trash_stack_push (GstTrashStack *stack, gpointer mem)
{
GstTrashStackElement *elem = (GstTrashStackElement *) mem;
g_mutex_lock (stack->lock);
elem->next = stack->head;
stack->head = elem;
g_mutex_unlock (stack->lock);
}
GST_INLINE_FUNC gpointer
gst_trash_stack_pop (GstTrashStack *stack)
{
GstTrashStackElement *head;
g_mutex_lock (stack->lock);
head = (GstTrashStackElement *) stack->head;
if (head)
stack->head = head->next;
g_mutex_unlock (stack->lock);
return head;
}
#endif
/*
* common functions
*/
GST_INLINE_FUNC GstTrashStack*
gst_trash_stack_new (void)
{
GstTrashStack *stack;
stack = g_new (GstTrashStack, 1);
gst_trash_stack_init (stack);
return stack;
}
GST_INLINE_FUNC void
gst_trash_stack_free (GstTrashStack *stack)
{
gst_trash_stack_destroy (stack);
g_free (stack);
}
#endif /* defined (GST_CAN_INLINE) || defined (__GST_TRASH_STACK_C__)*/
G_END_DECLS
#endif /* __GST_TRASH_STACK_H__ */