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/*****************************************************************************
Copyright (c) 2006, 2015, Oracle and/or its affiliates. All Rights Reserved.
Copyright (c) 2019, MariaDB Corporation.
This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; version 2 of the License.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA
*****************************************************************************/
#include "ut0list.h"
#include "mem0mem.h"
#include "ut0wqueue.h"
/*******************************************************************//**
@file ut/ut0wqueue.cc
A work queue
Created 4/26/2006 Osku Salerma
************************************************************************/
/* Work queue. */
struct ib_wqueue_t {
ib_mutex_t mutex; /*!< mutex protecting everything */
ib_list_t* items; /*!< work item list */
os_event_t event; /*!< event we use to signal additions to list;
os_event_set() and os_event_reset() are
protected by ib_wqueue_t::mutex */
};
/****************************************************************//**
Create a new work queue.
@return work queue */
ib_wqueue_t*
ib_wqueue_create(void)
/*===================*/
{
ib_wqueue_t* wq = static_cast<ib_wqueue_t*>(
ut_malloc_nokey(sizeof(*wq)));
/* Function ib_wqueue_create() has not been used anywhere,
not necessary to instrument this mutex */
mutex_create(LATCH_ID_WORK_QUEUE, &wq->mutex);
wq->items = ib_list_create();
wq->event = os_event_create(0);
return(wq);
}
/****************************************************************//**
Free a work queue. */
void
ib_wqueue_free(
/*===========*/
ib_wqueue_t* wq) /*!< in: work queue */
{
mutex_free(&wq->mutex);
ib_list_free(wq->items);
os_event_destroy(wq->event);
ut_free(wq);
}
/****************************************************************//**
Add a work item to the queue. */
void
ib_wqueue_add(
/*==========*/
ib_wqueue_t* wq, /*!< in: work queue */
void* item, /*!< in: work item */
mem_heap_t* heap) /*!< in: memory heap to use for allocating the
list node */
{
mutex_enter(&wq->mutex);
ib_list_add_last(wq->items, item, heap);
os_event_set(wq->event);
mutex_exit(&wq->mutex);
}
/****************************************************************//**
Wait for a work item to appear in the queue.
@return work item */
void*
ib_wqueue_wait(
/*===========*/
ib_wqueue_t* wq) /*!< in: work queue */
{
ib_list_node_t* node;
for (;;) {
os_event_wait(wq->event);
mutex_enter(&wq->mutex);
node = ib_list_get_first(wq->items);
if (node) {
ib_list_remove(wq->items, node);
if (!ib_list_get_first(wq->items)) {
/* We must reset the event when the list
gets emptied. */
os_event_reset(wq->event);
}
break;
}
mutex_exit(&wq->mutex);
}
mutex_exit(&wq->mutex);
return(node->data);
}
/********************************************************************
Wait for a work item to appear in the queue for specified time. */
void*
ib_wqueue_timedwait(
/*================*/
/* out: work item or NULL on timeout*/
ib_wqueue_t* wq, /* in: work queue */
ib_time_t wait_in_usecs) /* in: wait time in micro seconds */
{
ib_list_node_t* node = NULL;
for (;;) {
ulint error;
int64_t sig_count;
mutex_enter(&wq->mutex);
node = ib_list_get_first(wq->items);
if (node) {
ib_list_remove(wq->items, node);
mutex_exit(&wq->mutex);
break;
}
sig_count = os_event_reset(wq->event);
mutex_exit(&wq->mutex);
error = os_event_wait_time_low(wq->event,
(ulint) wait_in_usecs,
sig_count);
if (error == OS_SYNC_TIME_EXCEEDED) {
break;
}
}
return(node ? node->data : NULL);
}
/********************************************************************
Return first item on work queue or NULL if queue is empty
@return work item or NULL */
void*
ib_wqueue_nowait(
/*=============*/
ib_wqueue_t* wq) /*<! in: work queue */
{
ib_list_node_t* node = NULL;
mutex_enter(&wq->mutex);
if(!ib_list_is_empty(wq->items)) {
node = ib_list_get_first(wq->items);
if (node) {
ib_list_remove(wq->items, node);
}
}
/* We must reset the event when the list
gets emptied. */
if(ib_list_is_empty(wq->items)) {
os_event_reset(wq->event);
}
mutex_exit(&wq->mutex);
return (node ? node->data : NULL);
}
/** Check if queue is empty.
@param wq wait queue
@return whether the queue is empty */
bool ib_wqueue_is_empty(ib_wqueue_t* wq)
{
mutex_enter(&wq->mutex);
bool is_empty = ib_list_is_empty(wq->items);
mutex_exit(&wq->mutex);
return is_empty;
}
/********************************************************************
Get number of items on queue.
@return number of items on queue */
ulint
ib_wqueue_len(
/*==========*/
ib_wqueue_t* wq) /*<! in: work queue */
{
ulint len = 0;
mutex_enter(&wq->mutex);
len = ib_list_len(wq->items);
mutex_exit(&wq->mutex);
return(len);
}
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