mirror of
https://gitlab.freedesktop.org/gstreamer/gstreamer.git
synced 2024-12-24 17:20:36 +00:00
d68914ad64
Original commit message from CVS: * gst/gsttrashstack.h: Ooohh. a nasty one! After having a failed pop() from the stack, it's possible that the stack is empty. In that case, don't follow the NULL pointer.
198 lines
5.4 KiB
C
198 lines
5.4 KiB
C
/* 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;
|
|
};
|
|
|
|
typedef volatile gpointer gst_vgpointer;/* gtk-doc volatile workaround */
|
|
typedef volatile gulong gst_vgulong; /* gtk-doc volatile workaround */
|
|
|
|
struct _GstTrashStack {
|
|
gst_vgpointer head;
|
|
gst_vgulong 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 (USE_FAST_STACK_TRASH) && 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
|
|
* unlikely that we manage to grab the wrong head->next value.
|
|
*/
|
|
__asm__ __volatile__ (
|
|
" pushl %%ebx; \n\t"
|
|
" 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... */
|
|
" jz 20f; \n\t" /* success */
|
|
" testl %%eax, %%eax; \n\t" /* if (head == NULL) return */
|
|
" jnz 10b; \n\t" /* else we retry */
|
|
"20: \n\t"
|
|
" popl %%ebx \n"
|
|
: "=a" (head)
|
|
: "m" (*stack),
|
|
"a" (stack->head),
|
|
"d" (stack->count)
|
|
: "ecx"
|
|
);
|
|
|
|
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__ */
|