109 lines
2.8 KiB
C
109 lines
2.8 KiB
C
/* This file contains a simple message queue implementation to support both
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* the singlethread and the multithreaded driver implementation.
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*
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* Changes:
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* Oct 27, 2011 rewritten to use sys/queue.h (D.C. van Moolenbroek)
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* Aug 27, 2011 integrated into libblockdriver (A. Welzel)
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*/
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#include <minix/blockdriver_mt.h>
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#include <sys/queue.h>
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#include <assert.h>
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#include "const.h"
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#include "mq.h"
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#define MQ_SIZE 128
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struct mq_cell {
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message mess;
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int ipc_status;
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STAILQ_ENTRY(mq_cell) next;
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};
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static struct mq_cell pool[MQ_SIZE];
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static STAILQ_HEAD(queue, mq_cell) queue[MAX_DEVICES];
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static STAILQ_HEAD(free_list, mq_cell) free_list;
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/*===========================================================================*
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* mq_init *
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*===========================================================================*/
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void mq_init(void)
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{
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/* Initialize the message queues and message cells.
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*/
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int i;
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STAILQ_INIT(&free_list);
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for (i = 0; i < MAX_DEVICES; i++)
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STAILQ_INIT(&queue[i]);
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for (i = 0; i < MQ_SIZE; i++)
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STAILQ_INSERT_HEAD(&free_list, &pool[i], next);
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}
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/*===========================================================================*
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* mq_enqueue *
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*===========================================================================*/
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int mq_enqueue(device_id_t device_id, const message *mess,
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int ipc_status)
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{
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/* Add a message, including its IPC status, to the message queue of a device.
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* Return TRUE iff the message was added successfully.
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*/
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struct mq_cell *cell;
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assert(device_id >= 0 && device_id < MAX_DEVICES);
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if (STAILQ_EMPTY(&free_list))
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return FALSE;
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cell = STAILQ_FIRST(&free_list);
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STAILQ_REMOVE_HEAD(&free_list, next);
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cell->mess = *mess;
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cell->ipc_status = ipc_status;
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STAILQ_INSERT_TAIL(&queue[device_id], cell, next);
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return TRUE;
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}
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/*===========================================================================*
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* mq_isempty *
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*===========================================================================*/
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int mq_isempty(device_id_t device_id)
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{
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/* Return whether the message queue for the given device is empty.
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*/
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assert(device_id >= 0 && device_id < MAX_DEVICES);
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return STAILQ_EMPTY(&queue[device_id]);
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}
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/*===========================================================================*
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* mq_dequeue *
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*===========================================================================*/
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int mq_dequeue(device_id_t device_id, message *mess, int *ipc_status)
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{
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/* Return and remove a message, including its IPC status, from the message
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* queue of a thread. Return TRUE iff a message was available.
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*/
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struct mq_cell *cell;
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if (mq_isempty(device_id))
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return FALSE;
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cell = STAILQ_FIRST(&queue[device_id]);
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STAILQ_REMOVE_HEAD(&queue[device_id], next);
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*mess = cell->mess;
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*ipc_status = cell->ipc_status;
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STAILQ_INSERT_HEAD(&free_list, cell, next);
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return TRUE;
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}
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