qemu/main-loop.c
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   1/*
   2 * QEMU System Emulator
   3 *
   4 * Copyright (c) 2003-2008 Fabrice Bellard
   5 *
   6 * Permission is hereby granted, free of charge, to any person obtaining a copy
   7 * of this software and associated documentation files (the "Software"), to deal
   8 * in the Software without restriction, including without limitation the rights
   9 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10 * copies of the Software, and to permit persons to whom the Software is
  11 * furnished to do so, subject to the following conditions:
  12 *
  13 * The above copyright notice and this permission notice shall be included in
  14 * all copies or substantial portions of the Software.
  15 *
  16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22 * THE SOFTWARE.
  23 */
  24
  25#include "qemu-common.h"
  26#include "qemu/timer.h"
  27#include "qemu/sockets.h"       // struct in_addr needed for libslirp.h
  28#include "sysemu/qtest.h"
  29#include "slirp/libslirp.h"
  30#include "qemu/main-loop.h"
  31#include "block/aio.h"
  32
  33#ifndef _WIN32
  34
  35#include "qemu/compatfd.h"
  36
  37/* If we have signalfd, we mask out the signals we want to handle and then
  38 * use signalfd to listen for them.  We rely on whatever the current signal
  39 * handler is to dispatch the signals when we receive them.
  40 */
  41static void sigfd_handler(void *opaque)
  42{
  43    int fd = (intptr_t)opaque;
  44    struct qemu_signalfd_siginfo info;
  45    struct sigaction action;
  46    ssize_t len;
  47
  48    while (1) {
  49        do {
  50            len = read(fd, &info, sizeof(info));
  51        } while (len == -1 && errno == EINTR);
  52
  53        if (len == -1 && errno == EAGAIN) {
  54            break;
  55        }
  56
  57        if (len != sizeof(info)) {
  58            printf("read from sigfd returned %zd: %m\n", len);
  59            return;
  60        }
  61
  62        sigaction(info.ssi_signo, NULL, &action);
  63        if ((action.sa_flags & SA_SIGINFO) && action.sa_sigaction) {
  64            action.sa_sigaction(info.ssi_signo,
  65                                (siginfo_t *)&info, NULL);
  66        } else if (action.sa_handler) {
  67            action.sa_handler(info.ssi_signo);
  68        }
  69    }
  70}
  71
  72static int qemu_signal_init(void)
  73{
  74    int sigfd;
  75    sigset_t set;
  76
  77    /*
  78     * SIG_IPI must be blocked in the main thread and must not be caught
  79     * by sigwait() in the signal thread. Otherwise, the cpu thread will
  80     * not catch it reliably.
  81     */
  82    sigemptyset(&set);
  83    sigaddset(&set, SIG_IPI);
  84    sigaddset(&set, SIGIO);
  85    sigaddset(&set, SIGALRM);
  86    sigaddset(&set, SIGBUS);
  87    /* SIGINT cannot be handled via signalfd, so that ^C can be used
  88     * to interrupt QEMU when it is being run under gdb.  SIGHUP and
  89     * SIGTERM are also handled asynchronously, even though it is not
  90     * strictly necessary, because they use the same handler as SIGINT.
  91     */
  92    pthread_sigmask(SIG_BLOCK, &set, NULL);
  93
  94    sigdelset(&set, SIG_IPI);
  95    sigfd = qemu_signalfd(&set);
  96    if (sigfd == -1) {
  97        fprintf(stderr, "failed to create signalfd\n");
  98        return -errno;
  99    }
 100
 101    fcntl_setfl(sigfd, O_NONBLOCK);
 102
 103    qemu_set_fd_handler(sigfd, sigfd_handler, NULL, (void *)(intptr_t)sigfd);
 104
 105    return 0;
 106}
 107
 108#else /* _WIN32 */
 109
 110static int qemu_signal_init(void)
 111{
 112    return 0;
 113}
 114#endif
 115
 116static AioContext *qemu_aio_context;
 117static QEMUBH *qemu_notify_bh;
 118
 119static void notify_event_cb(void *opaque)
 120{
 121    /* No need to do anything; this bottom half is only used to
 122     * kick the kernel out of ppoll/poll/WaitForMultipleObjects.
 123     */
 124}
 125
 126AioContext *qemu_get_aio_context(void)
 127{
 128    return qemu_aio_context;
 129}
 130
 131void qemu_notify_event(void)
 132{
 133    if (!qemu_aio_context) {
 134        return;
 135    }
 136    qemu_bh_schedule(qemu_notify_bh);
 137}
 138
 139static GArray *gpollfds;
 140
 141int qemu_init_main_loop(Error **errp)
 142{
 143    int ret;
 144    GSource *src;
 145    Error *local_error = NULL;
 146
 147    init_clocks();
 148
 149    ret = qemu_signal_init();
 150    if (ret) {
 151        return ret;
 152    }
 153
 154    qemu_aio_context = aio_context_new(&local_error);
 155    qemu_notify_bh = qemu_bh_new(notify_event_cb, NULL);
 156    if (!qemu_aio_context) {
 157        error_propagate(errp, local_error);
 158        return -EMFILE;
 159    }
 160    gpollfds = g_array_new(FALSE, FALSE, sizeof(GPollFD));
 161    src = aio_get_g_source(qemu_aio_context);
 162    g_source_attach(src, NULL);
 163    g_source_unref(src);
 164    src = iohandler_get_g_source();
 165    g_source_attach(src, NULL);
 166    g_source_unref(src);
 167    return 0;
 168}
 169
 170static int max_priority;
 171
 172#ifndef _WIN32
 173static int glib_pollfds_idx;
 174static int glib_n_poll_fds;
 175
 176static void glib_pollfds_fill(int64_t *cur_timeout)
 177{
 178    GMainContext *context = g_main_context_default();
 179    int timeout = 0;
 180    int64_t timeout_ns;
 181    int n;
 182
 183    g_main_context_prepare(context, &max_priority);
 184
 185    glib_pollfds_idx = gpollfds->len;
 186    n = glib_n_poll_fds;
 187    do {
 188        GPollFD *pfds;
 189        glib_n_poll_fds = n;
 190        g_array_set_size(gpollfds, glib_pollfds_idx + glib_n_poll_fds);
 191        pfds = &g_array_index(gpollfds, GPollFD, glib_pollfds_idx);
 192        n = g_main_context_query(context, max_priority, &timeout, pfds,
 193                                 glib_n_poll_fds);
 194    } while (n != glib_n_poll_fds);
 195
 196    if (timeout < 0) {
 197        timeout_ns = -1;
 198    } else {
 199        timeout_ns = (int64_t)timeout * (int64_t)SCALE_MS;
 200    }
 201
 202    *cur_timeout = qemu_soonest_timeout(timeout_ns, *cur_timeout);
 203}
 204
 205static void glib_pollfds_poll(void)
 206{
 207    GMainContext *context = g_main_context_default();
 208    GPollFD *pfds = &g_array_index(gpollfds, GPollFD, glib_pollfds_idx);
 209
 210    if (g_main_context_check(context, max_priority, pfds, glib_n_poll_fds)) {
 211        g_main_context_dispatch(context);
 212    }
 213}
 214
 215#define MAX_MAIN_LOOP_SPIN (1000)
 216
 217static int os_host_main_loop_wait(int64_t timeout)
 218{
 219    int ret;
 220    static int spin_counter;
 221
 222    glib_pollfds_fill(&timeout);
 223
 224    /* If the I/O thread is very busy or we are incorrectly busy waiting in
 225     * the I/O thread, this can lead to starvation of the BQL such that the
 226     * VCPU threads never run.  To make sure we can detect the later case,
 227     * print a message to the screen.  If we run into this condition, create
 228     * a fake timeout in order to give the VCPU threads a chance to run.
 229     */
 230    if (!timeout && (spin_counter > MAX_MAIN_LOOP_SPIN)) {
 231        static bool notified;
 232
 233        if (!notified && !qtest_driver()) {
 234            fprintf(stderr,
 235                    "main-loop: WARNING: I/O thread spun for %d iterations\n",
 236                    MAX_MAIN_LOOP_SPIN);
 237            notified = true;
 238        }
 239
 240        timeout = SCALE_MS;
 241    }
 242
 243    if (timeout) {
 244        spin_counter = 0;
 245        qemu_mutex_unlock_iothread();
 246    } else {
 247        spin_counter++;
 248    }
 249
 250    ret = qemu_poll_ns((GPollFD *)gpollfds->data, gpollfds->len, timeout);
 251
 252    if (timeout) {
 253        qemu_mutex_lock_iothread();
 254    }
 255
 256    glib_pollfds_poll();
 257    return ret;
 258}
 259#else
 260/***********************************************************/
 261/* Polling handling */
 262
 263typedef struct PollingEntry {
 264    PollingFunc *func;
 265    void *opaque;
 266    struct PollingEntry *next;
 267} PollingEntry;
 268
 269static PollingEntry *first_polling_entry;
 270
 271int qemu_add_polling_cb(PollingFunc *func, void *opaque)
 272{
 273    PollingEntry **ppe, *pe;
 274    pe = g_malloc0(sizeof(PollingEntry));
 275    pe->func = func;
 276    pe->opaque = opaque;
 277    for(ppe = &first_polling_entry; *ppe != NULL; ppe = &(*ppe)->next);
 278    *ppe = pe;
 279    return 0;
 280}
 281
 282void qemu_del_polling_cb(PollingFunc *func, void *opaque)
 283{
 284    PollingEntry **ppe, *pe;
 285    for(ppe = &first_polling_entry; *ppe != NULL; ppe = &(*ppe)->next) {
 286        pe = *ppe;
 287        if (pe->func == func && pe->opaque == opaque) {
 288            *ppe = pe->next;
 289            g_free(pe);
 290            break;
 291        }
 292    }
 293}
 294
 295/***********************************************************/
 296/* Wait objects support */
 297typedef struct WaitObjects {
 298    int num;
 299    int revents[MAXIMUM_WAIT_OBJECTS + 1];
 300    HANDLE events[MAXIMUM_WAIT_OBJECTS + 1];
 301    WaitObjectFunc *func[MAXIMUM_WAIT_OBJECTS + 1];
 302    void *opaque[MAXIMUM_WAIT_OBJECTS + 1];
 303} WaitObjects;
 304
 305static WaitObjects wait_objects = {0};
 306
 307int qemu_add_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque)
 308{
 309    WaitObjects *w = &wait_objects;
 310    if (w->num >= MAXIMUM_WAIT_OBJECTS) {
 311        return -1;
 312    }
 313    w->events[w->num] = handle;
 314    w->func[w->num] = func;
 315    w->opaque[w->num] = opaque;
 316    w->revents[w->num] = 0;
 317    w->num++;
 318    return 0;
 319}
 320
 321void qemu_del_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque)
 322{
 323    int i, found;
 324    WaitObjects *w = &wait_objects;
 325
 326    found = 0;
 327    for (i = 0; i < w->num; i++) {
 328        if (w->events[i] == handle) {
 329            found = 1;
 330        }
 331        if (found) {
 332            w->events[i] = w->events[i + 1];
 333            w->func[i] = w->func[i + 1];
 334            w->opaque[i] = w->opaque[i + 1];
 335            w->revents[i] = w->revents[i + 1];
 336        }
 337    }
 338    if (found) {
 339        w->num--;
 340    }
 341}
 342
 343void qemu_fd_register(int fd)
 344{
 345    WSAEventSelect(fd, event_notifier_get_handle(&qemu_aio_context->notifier),
 346                   FD_READ | FD_ACCEPT | FD_CLOSE |
 347                   FD_CONNECT | FD_WRITE | FD_OOB);
 348}
 349
 350static int pollfds_fill(GArray *pollfds, fd_set *rfds, fd_set *wfds,
 351                        fd_set *xfds)
 352{
 353    int nfds = -1;
 354    int i;
 355
 356    for (i = 0; i < pollfds->len; i++) {
 357        GPollFD *pfd = &g_array_index(pollfds, GPollFD, i);
 358        int fd = pfd->fd;
 359        int events = pfd->events;
 360        if (events & G_IO_IN) {
 361            FD_SET(fd, rfds);
 362            nfds = MAX(nfds, fd);
 363        }
 364        if (events & G_IO_OUT) {
 365            FD_SET(fd, wfds);
 366            nfds = MAX(nfds, fd);
 367        }
 368        if (events & G_IO_PRI) {
 369            FD_SET(fd, xfds);
 370            nfds = MAX(nfds, fd);
 371        }
 372    }
 373    return nfds;
 374}
 375
 376static void pollfds_poll(GArray *pollfds, int nfds, fd_set *rfds,
 377                         fd_set *wfds, fd_set *xfds)
 378{
 379    int i;
 380
 381    for (i = 0; i < pollfds->len; i++) {
 382        GPollFD *pfd = &g_array_index(pollfds, GPollFD, i);
 383        int fd = pfd->fd;
 384        int revents = 0;
 385
 386        if (FD_ISSET(fd, rfds)) {
 387            revents |= G_IO_IN;
 388        }
 389        if (FD_ISSET(fd, wfds)) {
 390            revents |= G_IO_OUT;
 391        }
 392        if (FD_ISSET(fd, xfds)) {
 393            revents |= G_IO_PRI;
 394        }
 395        pfd->revents = revents & pfd->events;
 396    }
 397}
 398
 399static int os_host_main_loop_wait(int64_t timeout)
 400{
 401    GMainContext *context = g_main_context_default();
 402    GPollFD poll_fds[1024 * 2]; /* this is probably overkill */
 403    int select_ret = 0;
 404    int g_poll_ret, ret, i, n_poll_fds;
 405    PollingEntry *pe;
 406    WaitObjects *w = &wait_objects;
 407    gint poll_timeout;
 408    int64_t poll_timeout_ns;
 409    static struct timeval tv0;
 410    fd_set rfds, wfds, xfds;
 411    int nfds;
 412
 413    /* XXX: need to suppress polling by better using win32 events */
 414    ret = 0;
 415    for (pe = first_polling_entry; pe != NULL; pe = pe->next) {
 416        ret |= pe->func(pe->opaque);
 417    }
 418    if (ret != 0) {
 419        return ret;
 420    }
 421
 422    FD_ZERO(&rfds);
 423    FD_ZERO(&wfds);
 424    FD_ZERO(&xfds);
 425    nfds = pollfds_fill(gpollfds, &rfds, &wfds, &xfds);
 426    if (nfds >= 0) {
 427        select_ret = select(nfds + 1, &rfds, &wfds, &xfds, &tv0);
 428        if (select_ret != 0) {
 429            timeout = 0;
 430        }
 431        if (select_ret > 0) {
 432            pollfds_poll(gpollfds, nfds, &rfds, &wfds, &xfds);
 433        }
 434    }
 435
 436    g_main_context_prepare(context, &max_priority);
 437    n_poll_fds = g_main_context_query(context, max_priority, &poll_timeout,
 438                                      poll_fds, ARRAY_SIZE(poll_fds));
 439    g_assert(n_poll_fds <= ARRAY_SIZE(poll_fds));
 440
 441    for (i = 0; i < w->num; i++) {
 442        poll_fds[n_poll_fds + i].fd = (DWORD_PTR)w->events[i];
 443        poll_fds[n_poll_fds + i].events = G_IO_IN;
 444    }
 445
 446    if (poll_timeout < 0) {
 447        poll_timeout_ns = -1;
 448    } else {
 449        poll_timeout_ns = (int64_t)poll_timeout * (int64_t)SCALE_MS;
 450    }
 451
 452    poll_timeout_ns = qemu_soonest_timeout(poll_timeout_ns, timeout);
 453
 454    qemu_mutex_unlock_iothread();
 455    g_poll_ret = qemu_poll_ns(poll_fds, n_poll_fds + w->num, poll_timeout_ns);
 456
 457    qemu_mutex_lock_iothread();
 458    if (g_poll_ret > 0) {
 459        for (i = 0; i < w->num; i++) {
 460            w->revents[i] = poll_fds[n_poll_fds + i].revents;
 461        }
 462        for (i = 0; i < w->num; i++) {
 463            if (w->revents[i] && w->func[i]) {
 464                w->func[i](w->opaque[i]);
 465            }
 466        }
 467    }
 468
 469    if (g_main_context_check(context, max_priority, poll_fds, n_poll_fds)) {
 470        g_main_context_dispatch(context);
 471    }
 472
 473    return select_ret || g_poll_ret;
 474}
 475#endif
 476
 477int main_loop_wait(int nonblocking)
 478{
 479    int ret;
 480    uint32_t timeout = UINT32_MAX;
 481    int64_t timeout_ns;
 482
 483    if (nonblocking) {
 484        timeout = 0;
 485    }
 486
 487    /* poll any events */
 488    g_array_set_size(gpollfds, 0); /* reset for new iteration */
 489    /* XXX: separate device handlers from system ones */
 490#ifdef CONFIG_SLIRP
 491    slirp_pollfds_fill(gpollfds, &timeout);
 492#endif
 493
 494    if (timeout == UINT32_MAX) {
 495        timeout_ns = -1;
 496    } else {
 497        timeout_ns = (uint64_t)timeout * (int64_t)(SCALE_MS);
 498    }
 499
 500    timeout_ns = qemu_soonest_timeout(timeout_ns,
 501                                      timerlistgroup_deadline_ns(
 502                                          &main_loop_tlg));
 503
 504    ret = os_host_main_loop_wait(timeout_ns);
 505#ifdef CONFIG_SLIRP
 506    slirp_pollfds_poll(gpollfds, (ret < 0));
 507#endif
 508
 509    /* CPU thread can infinitely wait for event after
 510       missing the warp */
 511    qemu_clock_warp(QEMU_CLOCK_VIRTUAL);
 512    qemu_clock_run_all_timers();
 513
 514    return ret;
 515}
 516
 517/* Functions to operate on the main QEMU AioContext.  */
 518
 519QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque)
 520{
 521    return aio_bh_new(qemu_aio_context, cb, opaque);
 522}
 523