Archipelago » qemu

/*

 * QEMU posix-aio emulation

 *

 * Copyright IBM, Corp. 2008

 *

 * Authors:

 *  Anthony Liguori   <aliguori@us.ibm.com>

 *

 * This work is licensed under the terms of the GNU GPL, version 2.  See

 * the COPYING file in the top-level directory.

 *

 */

#include <pthread.h>

#include <unistd.h>

#include <errno.h>

#include <time.h>

#include <string.h>

#include <stdlib.h>

#include <stdio.h>

#include "osdep.h"

#include "posix-aio-compat.h"

static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;

static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;

static pthread_t thread_id;

static pthread_attr_t attr;

static int max_threads = 64;

static int cur_threads = 0;

static int idle_threads = 0;

static TAILQ_HEAD(, qemu_paiocb) request_list;

static void die2(int err, const char *what)

{

    fprintf(stderr, "%s failed: %s\n", what, strerror(err));

    abort();

}

static void die(const char *what)

{

    die2(errno, what);

}

static void mutex_lock(pthread_mutex_t *mutex)

{

    int ret = pthread_mutex_lock(mutex);

    if (ret) die2(ret, "pthread_mutex_lock");

}

static void mutex_unlock(pthread_mutex_t *mutex)

{

    int ret = pthread_mutex_unlock(mutex);

    if (ret) die2(ret, "pthread_mutex_unlock");

}

static int cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,

                           struct timespec *ts)

{

    int ret = pthread_cond_timedwait(cond, mutex, ts);

    if (ret && ret != ETIMEDOUT) die2(ret, "pthread_cond_timedwait");

    return ret;

}

static void cond_signal(pthread_cond_t *cond)

{

    int ret = pthread_cond_signal(cond);

    if (ret) die2(ret, "pthread_cond_signal");

}

static void thread_create(pthread_t *thread, pthread_attr_t *attr,

                          void *(*start_routine)(void*), void *arg)

{

    int ret = pthread_create(thread, attr, start_routine, arg);

    if (ret) die2(ret, "pthread_create");

}

static void *aio_thread(void *unused)

{

    pid_t pid;

    sigset_t set;

    pid = getpid();

    /* block all signals */

    if (sigfillset(&set)) die("sigfillset");

    if (sigprocmask(SIG_BLOCK, &set, NULL)) die("sigprocmask");

    while (1) {

        struct qemu_paiocb *aiocb;

        size_t offset;

        int ret = 0;

        qemu_timeval tv;

        struct timespec ts;

        qemu_gettimeofday(&tv);

        ts.tv_sec = tv.tv_sec + 10;

        ts.tv_nsec = 0;

        mutex_lock(&lock);

        while (TAILQ_EMPTY(&request_list) &&

               !(ret == ETIMEDOUT)) {

            ret = cond_timedwait(&cond, &lock, &ts);

        }

        if (TAILQ_EMPTY(&request_list))

            break;

        aiocb = TAILQ_FIRST(&request_list);

        TAILQ_REMOVE(&request_list, aiocb, node);

        offset = 0;

        aiocb->active = 1;

        idle_threads--;

        mutex_unlock(&lock);

        while (offset < aiocb->aio_nbytes) {

            ssize_t len;

            if (aiocb->is_write)

                len = pwrite(aiocb->aio_fildes,

                             (const char *)aiocb->aio_buf + offset,

                             aiocb->aio_nbytes - offset,

                             aiocb->aio_offset + offset);

            else

                len = pread(aiocb->aio_fildes,

                            (char *)aiocb->aio_buf + offset,

                            aiocb->aio_nbytes - offset,

                            aiocb->aio_offset + offset);

            if (len == -1 && errno == EINTR)

                continue;

            else if (len == -1) {

                offset = -errno;

                break;

            } else if (len == 0)

                break;

            offset += len;

        }

        mutex_lock(&lock);

        aiocb->ret = offset;

        idle_threads++;

        mutex_unlock(&lock);

        if (kill(pid, aiocb->ev_signo)) die("kill failed");

    }

    idle_threads--;

    cur_threads--;

    mutex_unlock(&lock);

    return NULL;

}

static void spawn_thread(void)

{

    cur_threads++;

    idle_threads++;

    thread_create(&thread_id, &attr, aio_thread, NULL);

}

int qemu_paio_init(struct qemu_paioinit *aioinit)

{

    int ret;

    ret = pthread_attr_init(&attr);

    if (ret) die2(ret, "pthread_attr_init");

    ret = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);

    if (ret) die2(ret, "pthread_attr_setdetachstate");

    TAILQ_INIT(&request_list);

    return 0;

}

static int qemu_paio_submit(struct qemu_paiocb *aiocb, int is_write)

{

    aiocb->is_write = is_write;

    aiocb->ret = -EINPROGRESS;

    aiocb->active = 0;

    mutex_lock(&lock);

    if (idle_threads == 0 && cur_threads < max_threads)

        spawn_thread();

    TAILQ_INSERT_TAIL(&request_list, aiocb, node);

    mutex_unlock(&lock);

    cond_signal(&cond);

    return 0;

}

int qemu_paio_read(struct qemu_paiocb *aiocb)

{

    return qemu_paio_submit(aiocb, 0);

}

int qemu_paio_write(struct qemu_paiocb *aiocb)

{

    return qemu_paio_submit(aiocb, 1);

}

ssize_t qemu_paio_return(struct qemu_paiocb *aiocb)

{

    ssize_t ret;

    mutex_lock(&lock);

    ret = aiocb->ret;

    mutex_unlock(&lock);

    return ret;

}

int qemu_paio_error(struct qemu_paiocb *aiocb)

{

    ssize_t ret = qemu_paio_return(aiocb);

    if (ret < 0)

        ret = -ret;

    else

        ret = 0;

    return ret;

}

int qemu_paio_cancel(int fd, struct qemu_paiocb *aiocb)

{

    int ret;

    mutex_lock(&lock);

    if (!aiocb->active) {

        TAILQ_REMOVE(&request_list, aiocb, node);

        aiocb->ret = -ECANCELED;

        ret = QEMU_PAIO_CANCELED;

    } else if (aiocb->ret == -EINPROGRESS)

        ret = QEMU_PAIO_NOTCANCELED;

    else

        ret = QEMU_PAIO_ALLDONE;

    mutex_unlock(&lock);

    return ret;

}