minix/lib/libblockdriver/driver_mt.c
2011-12-12 14:13:05 +01:00

507 lines
14 KiB
C

/* This file contains the multithreaded driver interface.
*
* Changes:
* Aug 27, 2011 created (A. Welzel)
*
* The entry points into this file are:
* blockdriver_mt_task: the main message loop of the driver
* blockdriver_mt_terminate: break out of the main message loop
* blockdriver_mt_sleep: put the current thread to sleep
* blockdriver_mt_wakeup: wake up a sleeping thread
* blockdriver_mt_set_workers:set the number of worker threads
*/
#include <minix/blockdriver_mt.h>
#include <minix/mthread.h>
#include <assert.h>
#include "const.h"
#include "driver.h"
#include "mq.h"
/* A thread ID is composed of a device ID and a per-device worker thread ID.
* All thread IDs must be in the range 0..(MAX_THREADS-1) inclusive.
*/
#define MAKE_TID(did, wid) ((did) * MAX_WORKERS + (wid))
#define TID_DEVICE(tid) ((tid) / MAX_WORKERS)
#define TID_WORKER(tid) ((tid) % MAX_WORKERS)
typedef int worker_id_t;
typedef enum {
STATE_DEAD,
STATE_RUNNING,
STATE_BUSY,
STATE_EXITED
} worker_state;
/* Structure with information about a worker thread. */
typedef struct {
device_id_t device_id;
worker_id_t worker_id;
worker_state state;
mthread_thread_t mthread;
mthread_event_t sleep_event;
} worker_t;
/* Structure with information about a device. */
typedef struct {
device_id_t id;
unsigned int workers;
worker_t worker[MAX_WORKERS];
mthread_event_t queue_event;
mthread_rwlock_t barrier;
} device_t;
PRIVATE struct blockdriver *bdtab;
PRIVATE int running = FALSE;
PRIVATE mthread_key_t worker_key;
PRIVATE device_t device[MAX_DEVICES];
PRIVATE worker_t *exited[MAX_THREADS];
PRIVATE int num_exited = 0;
/*===========================================================================*
* enqueue *
*===========================================================================*/
PRIVATE void enqueue(device_t *dp, const message *m_src, int ipc_status)
{
/* Enqueue a message into the device's queue, and signal the event.
* Must be called from the master thread.
*/
if (!mq_enqueue(dp->id, m_src, ipc_status))
panic("blockdriver_mt: enqueue failed (message queue full)");
mthread_event_fire(&dp->queue_event);
}
/*===========================================================================*
* try_dequeue *
*===========================================================================*/
PRIVATE int try_dequeue(device_t *dp, message *m_dst, int *ipc_status)
{
/* See if a message can be dequeued from the current worker thread's device
* queue. If so, dequeue the message and return TRUE. If not, return FALSE.
* Must be called from a worker thread. Does not block.
*/
return mq_dequeue(dp->id, m_dst, ipc_status);
}
/*===========================================================================*
* dequeue *
*===========================================================================*/
PRIVATE int dequeue(device_t *dp, worker_t *wp, message *m_dst,
int *ipc_status)
{
/* Dequeue a message from the current worker thread's device queue. Block the
* current thread if necessary. Must be called from a worker thread. Either
* succeeds with a message (TRUE) or indicates that the thread should be
* terminated (FALSE).
*/
do {
mthread_event_wait(&dp->queue_event);
/* If we were woken up as a result of terminate or set_workers, break
* out of the loop and terminate the thread.
*/
if (!running || wp->worker_id >= dp->workers)
return FALSE;
} while (!try_dequeue(dp, m_dst, ipc_status));
return TRUE;
}
/*===========================================================================*
* is_transfer_req *
*===========================================================================*/
PRIVATE int is_transfer_req(int type)
{
/* Return whether the given block device request is a transfer request.
*/
switch (type) {
case BDEV_READ:
case BDEV_WRITE:
case BDEV_GATHER:
case BDEV_SCATTER:
return TRUE;
default:
return FALSE;
}
}
/*===========================================================================*
* worker_thread *
*===========================================================================*/
PRIVATE void *worker_thread(void *param)
{
/* The worker thread loop. Set up the thread-specific reference to itself and
* start looping. The loop consists of blocking dequeing and handling messages.
* After handling a message, the thread might have been stopped, so we check
* for this condition and exit if so.
*/
worker_t *wp;
device_t *dp;
thread_id_t tid;
message m;
int ipc_status, r;
wp = (worker_t *) param;
assert(wp != NULL);
dp = &device[wp->device_id];
tid = MAKE_TID(wp->device_id, wp->worker_id);
if (mthread_setspecific(worker_key, wp))
panic("blockdriver_mt: could not save local thread pointer");
while (running && wp->worker_id < dp->workers) {
/* See if a new message is available right away. */
if (!try_dequeue(dp, &m, &ipc_status)) {
/* If not, block waiting for a new message or a thread
* termination event.
*/
if (!dequeue(dp, wp, &m, &ipc_status))
break;
}
/* Even if the thread was stopped before, a new message resumes it. */
wp->state = STATE_BUSY;
/* If the request is a transfer request, we acquire the read barrier
* lock. Otherwise, we acquire the write lock.
*/
if (is_transfer_req(m.m_type))
mthread_rwlock_rdlock(&dp->barrier);
else
mthread_rwlock_wrlock(&dp->barrier);
/* Handle the request and send a reply. */
r = blockdriver_handle_request(bdtab, &m, tid);
blockdriver_reply(&m, ipc_status, r);
/* Switch the thread back to running state, and unlock the barrier. */
wp->state = STATE_RUNNING;
mthread_rwlock_unlock(&dp->barrier);
}
/* Clean up and terminate this thread. */
if (mthread_setspecific(worker_key, NULL))
panic("blockdriver_mt: could not delete local thread pointer");
wp->state = STATE_EXITED;
exited[num_exited++] = wp;
return NULL;
}
/*===========================================================================*
* master_create_worker *
*===========================================================================*/
PRIVATE void master_create_worker(worker_t *wp, worker_id_t worker_id,
device_id_t device_id)
{
/* Start a new worker thread.
*/
int r;
wp->device_id = device_id;
wp->worker_id = worker_id;
wp->state = STATE_RUNNING;
/* Initialize synchronization primitives. */
mthread_event_init(&wp->sleep_event);
r = mthread_create(&wp->mthread, NULL /*attr*/, worker_thread, (void *) wp);
if (r != 0)
panic("blockdriver_mt: could not start thread %d (%d)", worker_id, r);
}
/*===========================================================================*
* master_destroy_worker *
*===========================================================================*/
PRIVATE void master_destroy_worker(worker_t *wp)
{
/* Clean up resources used by an exited worker thread.
*/
assert(wp != NULL);
assert(wp->state == STATE_EXITED);
/* Join the thread. */
if (mthread_join(wp->mthread, NULL))
panic("blockdriver_mt: could not join thread %d", wp->worker_id);
/* Destroy resources. */
mthread_event_destroy(&wp->sleep_event);
wp->state = STATE_DEAD;
}
/*===========================================================================*
* master_handle_exits *
*===========================================================================*/
PRIVATE void master_handle_exits(void)
{
/* Destroy the remains of all exited threads.
*/
int i;
for (i = 0; i < num_exited; i++)
master_destroy_worker(exited[i]);
num_exited = 0;
}
/*===========================================================================*
* master_handle_request *
*===========================================================================*/
PRIVATE void master_handle_request(message *m_ptr, int ipc_status)
{
/* For real request messages, query the device ID, start a thread if none is
* free and the maximum number of threads for that device has not yet been
* reached, and enqueue the message in the devices's message queue.
*/
device_id_t id;
worker_t *wp;
device_t *dp;
int r, wid;
/* If this is not a block driver request, we cannot get the minor device
* associated with it, and thus we can not tell which thread should process
* it either. In that case, the master thread has to handle it instead.
*/
if (!IS_BDEV_RQ(m_ptr->m_type)) {
/* Process as 'other' message. */
r = blockdriver_handle_request(bdtab, m_ptr, MAIN_THREAD);
blockdriver_reply(m_ptr, ipc_status, r);
return;
}
/* Query the device ID. Upon failure, send the error code to the caller. */
r = (*bdtab->bdr_device)(m_ptr->BDEV_MINOR, &id);
if (r != OK) {
blockdriver_reply(m_ptr, ipc_status, r);
return;
}
/* Look up the device control block. */
assert(id >= 0 && id < MAX_DEVICES);
dp = &device[id];
/* Find the first non-busy worker thread. */
for (wid = 0; wid < dp->workers; wid++)
if (dp->worker[wid].state != STATE_BUSY)
break;
/* If the worker thread is dead, start a thread now, unless we have already
* reached the maximum number of threads.
*/
if (wid < dp->workers) {
wp = &dp->worker[wid];
assert(wp->state != STATE_EXITED);
/* If the non-busy thread has not yet been created, create one now. */
if (wp->state == STATE_DEAD)
master_create_worker(wp, wid, dp->id);
}
/* Enqueue the message at the device queue. */
enqueue(dp, m_ptr, ipc_status);
}
/*===========================================================================*
* master_init *
*===========================================================================*/
PRIVATE void master_init(struct blockdriver *bdp)
{
/* Initialize the state of the master thread.
*/
int i, j;
assert(bdp != NULL);
assert(bdp->bdr_device != NULL);
mthread_init();
bdtab = bdp;
/* Initialize device-specific data structures. */
for (i = 0; i < MAX_DEVICES; i++) {
device[i].id = i;
device[i].workers = 1;
mthread_event_init(&device[i].queue_event);
mthread_rwlock_init(&device[i].barrier);
for (j = 0; j < MAX_WORKERS; j++)
device[i].worker[j].state = STATE_DEAD;
}
/* Initialize a per-thread key, where each worker thread stores its own
* reference to the worker structure.
*/
if (mthread_key_create(&worker_key, NULL))
panic("blockdriver_mt: error initializing worker key");
}
/*===========================================================================*
* blockdriver_mt_get_tid *
*===========================================================================*/
PUBLIC thread_id_t blockdriver_mt_get_tid(void)
{
/* Return back the ID of this thread.
*/
worker_t *wp;
wp = (worker_t *) mthread_getspecific(worker_key);
if (wp == NULL)
panic("blockdriver_mt: master thread cannot query thread ID\n");
return MAKE_TID(wp->device_id, wp->worker_id);
}
/*===========================================================================*
* blockdriver_mt_receive *
*===========================================================================*/
PRIVATE void blockdriver_mt_receive(message *m_ptr, int *ipc_status)
{
/* Receive a message.
*/
int r;
r = sef_receive_status(ANY, m_ptr, ipc_status);
if (r != OK)
panic("blockdriver_mt: sef_receive_status() returned %d", r);
}
/*===========================================================================*
* blockdriver_mt_task *
*===========================================================================*/
PUBLIC void blockdriver_mt_task(struct blockdriver *driver_tab)
{
/* The multithreaded driver task.
*/
int ipc_status, i;
message mess;
/* Initialize first if necessary. */
if (!running) {
master_init(driver_tab);
running = TRUE;
}
/* The main message loop. */
while (running) {
/* Receive a message. */
blockdriver_mt_receive(&mess, &ipc_status);
/* Dispatch the message. */
if (is_ipc_notify(ipc_status))
blockdriver_handle_notify(bdtab, &mess);
else
master_handle_request(&mess, ipc_status);
/* Let other threads run. */
mthread_yield_all();
/* Clean up any exited threads. */
if (num_exited > 0)
master_handle_exits();
}
/* Free up resources. */
for (i = 0; i < MAX_DEVICES; i++)
mthread_event_destroy(&device[i].queue_event);
}
/*===========================================================================*
* blockdriver_mt_terminate *
*===========================================================================*/
PUBLIC void blockdriver_mt_terminate(void)
{
/* Instruct libblockdriver to shut down.
*/
running = FALSE;
}
/*===========================================================================*
* blockdriver_mt_sleep *
*===========================================================================*/
PUBLIC void blockdriver_mt_sleep(void)
{
/* Let the current thread sleep until it gets woken up by the master thread.
*/
worker_t *wp;
wp = (worker_t *) mthread_getspecific(worker_key);
if (wp == NULL)
panic("blockdriver_mt: master thread cannot sleep");
mthread_event_wait(&wp->sleep_event);
}
/*===========================================================================*
* blockdriver_mt_wakeup *
*===========================================================================*/
PUBLIC void blockdriver_mt_wakeup(thread_id_t id)
{
/* Wake up a sleeping worker thread from the master thread.
*/
worker_t *wp;
device_id_t device_id;
worker_id_t worker_id;
device_id = TID_DEVICE(id);
worker_id = TID_WORKER(id);
assert(device_id >= 0 && device_id < MAX_DEVICES);
assert(worker_id >= 0 && worker_id < MAX_WORKERS);
wp = &device[device_id].worker[worker_id];
assert(wp->state == STATE_RUNNING || wp->state == STATE_BUSY);
mthread_event_fire(&wp->sleep_event);
}
/*===========================================================================*
* blockdriver_mt_set_workers *
*===========================================================================*/
PUBLIC void blockdriver_mt_set_workers(device_id_t id, int workers)
{
/* Set the number of worker threads for the given device.
*/
device_t *dp;
assert(id >= 0 && id < MAX_DEVICES);
if (workers > MAX_WORKERS)
workers = MAX_WORKERS;
dp = &device[id];
/* If we are cleaning up, wake up all threads waiting on a queue event. */
if (workers == 1 && dp->workers > workers)
mthread_event_fire_all(&dp->queue_event);
dp->workers = workers;
}