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qemu-e2k/main-loop.c
Chrysostomos Nanakos 2f78e491d7 async: aio_context_new(): Handle event_notifier_init failure 
On a system with a low limit of open files the initialization
of the event notifier could fail and QEMU exits without printing any
error information to the user.

The problem can be easily reproduced by enforcing a low limit of open
files and start QEMU with enough I/O threads to hit this limit.

The same problem raises, without the creation of I/O threads, while
QEMU initializes the main event loop by enforcing an even lower limit of
open files.

This commit adds an error message on failure:

 # qemu [...] -object iothread,id=iothread0 -object iothread,id=iothread1
 qemu: Failed to initialize event notifier: Too many open files in system

Signed-off-by: Chrysostomos Nanakos <cnanakos@grnet.gr>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-09-22 11:39:48 +01:00

506 lines
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/*
* QEMU System Emulator
*
* Copyright (c) 2003-2008 Fabrice Bellard
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "qemu-common.h"
#include "qemu/timer.h"
#include "qemu/sockets.h" // struct in_addr needed for libslirp.h
#include "sysemu/qtest.h"
#include "slirp/libslirp.h"
#include "qemu/main-loop.h"
#include "block/aio.h"
#ifndef _WIN32
#include "qemu/compatfd.h"
/* If we have signalfd, we mask out the signals we want to handle and then
* use signalfd to listen for them. We rely on whatever the current signal
* handler is to dispatch the signals when we receive them.
*/
static void sigfd_handler(void *opaque)
{
int fd = (intptr_t)opaque;
struct qemu_signalfd_siginfo info;
struct sigaction action;
ssize_t len;
while (1) {
do {
len = read(fd, &info, sizeof(info));
} while (len == -1 && errno == EINTR);
if (len == -1 && errno == EAGAIN) {
break;
}
if (len != sizeof(info)) {
printf("read from sigfd returned %zd: %m\n", len);
return;
}
sigaction(info.ssi_signo, NULL, &action);
if ((action.sa_flags & SA_SIGINFO) && action.sa_sigaction) {
action.sa_sigaction(info.ssi_signo,
(siginfo_t *)&info, NULL);
} else if (action.sa_handler) {
action.sa_handler(info.ssi_signo);
}
}
}
static int qemu_signal_init(void)
{
int sigfd;
sigset_t set;
/*
* SIG_IPI must be blocked in the main thread and must not be caught
* by sigwait() in the signal thread. Otherwise, the cpu thread will
* not catch it reliably.
*/
sigemptyset(&set);
sigaddset(&set, SIG_IPI);
sigaddset(&set, SIGIO);
sigaddset(&set, SIGALRM);
sigaddset(&set, SIGBUS);
pthread_sigmask(SIG_BLOCK, &set, NULL);
sigdelset(&set, SIG_IPI);
sigfd = qemu_signalfd(&set);
if (sigfd == -1) {
fprintf(stderr, "failed to create signalfd\n");
return -errno;
}
fcntl_setfl(sigfd, O_NONBLOCK);
qemu_set_fd_handler2(sigfd, NULL, sigfd_handler, NULL,
(void *)(intptr_t)sigfd);
return 0;
}
#else /* _WIN32 */
static int qemu_signal_init(void)
{
return 0;
}
#endif
static AioContext *qemu_aio_context;
AioContext *qemu_get_aio_context(void)
{
return qemu_aio_context;
}
void qemu_notify_event(void)
{
if (!qemu_aio_context) {
return;
}
aio_notify(qemu_aio_context);
}
static GArray *gpollfds;
int qemu_init_main_loop(Error **errp)
{
int ret;
GSource *src;
Error *local_error = NULL;
init_clocks();
ret = qemu_signal_init();
if (ret) {
return ret;
}
qemu_aio_context = aio_context_new(&local_error);
if (!qemu_aio_context) {
error_propagate(errp, local_error);
return -EMFILE;
}
gpollfds = g_array_new(FALSE, FALSE, sizeof(GPollFD));
src = aio_get_g_source(qemu_aio_context);
g_source_attach(src, NULL);
g_source_unref(src);
return 0;
}
static int max_priority;
#ifndef _WIN32
static int glib_pollfds_idx;
static int glib_n_poll_fds;
static void glib_pollfds_fill(int64_t *cur_timeout)
{
GMainContext *context = g_main_context_default();
int timeout = 0;
int64_t timeout_ns;
int n;
g_main_context_prepare(context, &max_priority);
glib_pollfds_idx = gpollfds->len;
n = glib_n_poll_fds;
do {
GPollFD *pfds;
glib_n_poll_fds = n;
g_array_set_size(gpollfds, glib_pollfds_idx + glib_n_poll_fds);
pfds = &g_array_index(gpollfds, GPollFD, glib_pollfds_idx);
n = g_main_context_query(context, max_priority, &timeout, pfds,
glib_n_poll_fds);
} while (n != glib_n_poll_fds);
if (timeout < 0) {
timeout_ns = -1;
} else {
timeout_ns = (int64_t)timeout * (int64_t)SCALE_MS;
}
*cur_timeout = qemu_soonest_timeout(timeout_ns, *cur_timeout);
}
static void glib_pollfds_poll(void)
{
GMainContext *context = g_main_context_default();
GPollFD *pfds = &g_array_index(gpollfds, GPollFD, glib_pollfds_idx);
if (g_main_context_check(context, max_priority, pfds, glib_n_poll_fds)) {
g_main_context_dispatch(context);
}
}
#define MAX_MAIN_LOOP_SPIN (1000)
static int os_host_main_loop_wait(int64_t timeout)
{
int ret;
static int spin_counter;
glib_pollfds_fill(&timeout);
/* If the I/O thread is very busy or we are incorrectly busy waiting in
* the I/O thread, this can lead to starvation of the BQL such that the
* VCPU threads never run. To make sure we can detect the later case,
* print a message to the screen. If we run into this condition, create
* a fake timeout in order to give the VCPU threads a chance to run.
*/
if (!timeout && (spin_counter > MAX_MAIN_LOOP_SPIN)) {
static bool notified;
if (!notified && !qtest_enabled()) {
fprintf(stderr,
"main-loop: WARNING: I/O thread spun for %d iterations\n",
MAX_MAIN_LOOP_SPIN);
notified = true;
}
timeout = SCALE_MS;
}
if (timeout) {
spin_counter = 0;
qemu_mutex_unlock_iothread();
} else {
spin_counter++;
}
ret = qemu_poll_ns((GPollFD *)gpollfds->data, gpollfds->len, timeout);
if (timeout) {
qemu_mutex_lock_iothread();
}
glib_pollfds_poll();
return ret;
}
#else
/***********************************************************/
/* Polling handling */
typedef struct PollingEntry {
PollingFunc *func;
void *opaque;
struct PollingEntry *next;
} PollingEntry;
static PollingEntry *first_polling_entry;
int qemu_add_polling_cb(PollingFunc *func, void *opaque)
{
PollingEntry **ppe, *pe;
pe = g_malloc0(sizeof(PollingEntry));
pe->func = func;
pe->opaque = opaque;
for(ppe = &first_polling_entry; *ppe != NULL; ppe = &(*ppe)->next);
*ppe = pe;
return 0;
}
void qemu_del_polling_cb(PollingFunc *func, void *opaque)
{
PollingEntry **ppe, *pe;
for(ppe = &first_polling_entry; *ppe != NULL; ppe = &(*ppe)->next) {
pe = *ppe;
if (pe->func == func && pe->opaque == opaque) {
*ppe = pe->next;
g_free(pe);
break;
}
}
}
/***********************************************************/
/* Wait objects support */
typedef struct WaitObjects {
int num;
int revents[MAXIMUM_WAIT_OBJECTS + 1];
HANDLE events[MAXIMUM_WAIT_OBJECTS + 1];
WaitObjectFunc *func[MAXIMUM_WAIT_OBJECTS + 1];
void *opaque[MAXIMUM_WAIT_OBJECTS + 1];
} WaitObjects;
static WaitObjects wait_objects = {0};
int qemu_add_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque)
{
WaitObjects *w = &wait_objects;
if (w->num >= MAXIMUM_WAIT_OBJECTS) {
return -1;
}
w->events[w->num] = handle;
w->func[w->num] = func;
w->opaque[w->num] = opaque;
w->revents[w->num] = 0;
w->num++;
return 0;
}
void qemu_del_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque)
{
int i, found;
WaitObjects *w = &wait_objects;
found = 0;
for (i = 0; i < w->num; i++) {
if (w->events[i] == handle) {
found = 1;
}
if (found) {
w->events[i] = w->events[i + 1];
w->func[i] = w->func[i + 1];
w->opaque[i] = w->opaque[i + 1];
w->revents[i] = w->revents[i + 1];
}
}
if (found) {
w->num--;
}
}
void qemu_fd_register(int fd)
{
WSAEventSelect(fd, event_notifier_get_handle(&qemu_aio_context->notifier),
FD_READ | FD_ACCEPT | FD_CLOSE |
FD_CONNECT | FD_WRITE | FD_OOB);
}
static int pollfds_fill(GArray *pollfds, fd_set *rfds, fd_set *wfds,
fd_set *xfds)
{
int nfds = -1;
int i;
for (i = 0; i < pollfds->len; i++) {
GPollFD *pfd = &g_array_index(pollfds, GPollFD, i);
int fd = pfd->fd;
int events = pfd->events;
if (events & G_IO_IN) {
FD_SET(fd, rfds);
nfds = MAX(nfds, fd);
}
if (events & G_IO_OUT) {
FD_SET(fd, wfds);
nfds = MAX(nfds, fd);
}
if (events & G_IO_PRI) {
FD_SET(fd, xfds);
nfds = MAX(nfds, fd);
}
}
return nfds;
}
static void pollfds_poll(GArray *pollfds, int nfds, fd_set *rfds,
fd_set *wfds, fd_set *xfds)
{
int i;
for (i = 0; i < pollfds->len; i++) {
GPollFD *pfd = &g_array_index(pollfds, GPollFD, i);
int fd = pfd->fd;
int revents = 0;
if (FD_ISSET(fd, rfds)) {
revents |= G_IO_IN;
}
if (FD_ISSET(fd, wfds)) {
revents |= G_IO_OUT;
}
if (FD_ISSET(fd, xfds)) {
revents |= G_IO_PRI;
}
pfd->revents = revents & pfd->events;
}
}
static int os_host_main_loop_wait(int64_t timeout)
{
GMainContext *context = g_main_context_default();
GPollFD poll_fds[1024 * 2]; /* this is probably overkill */
int select_ret = 0;
int g_poll_ret, ret, i, n_poll_fds;
PollingEntry *pe;
WaitObjects *w = &wait_objects;
gint poll_timeout;
int64_t poll_timeout_ns;
static struct timeval tv0;
fd_set rfds, wfds, xfds;
int nfds;
/* XXX: need to suppress polling by better using win32 events */
ret = 0;
for (pe = first_polling_entry; pe != NULL; pe = pe->next) {
ret |= pe->func(pe->opaque);
}
if (ret != 0) {
return ret;
}
FD_ZERO(&rfds);
FD_ZERO(&wfds);
FD_ZERO(&xfds);
nfds = pollfds_fill(gpollfds, &rfds, &wfds, &xfds);
if (nfds >= 0) {
select_ret = select(nfds + 1, &rfds, &wfds, &xfds, &tv0);
if (select_ret != 0) {
timeout = 0;
}
if (select_ret > 0) {
pollfds_poll(gpollfds, nfds, &rfds, &wfds, &xfds);
}
}
g_main_context_prepare(context, &max_priority);
n_poll_fds = g_main_context_query(context, max_priority, &poll_timeout,
poll_fds, ARRAY_SIZE(poll_fds));
g_assert(n_poll_fds <= ARRAY_SIZE(poll_fds));
for (i = 0; i < w->num; i++) {
poll_fds[n_poll_fds + i].fd = (DWORD_PTR)w->events[i];
poll_fds[n_poll_fds + i].events = G_IO_IN;
}
if (poll_timeout < 0) {
poll_timeout_ns = -1;
} else {
poll_timeout_ns = (int64_t)poll_timeout * (int64_t)SCALE_MS;
}
poll_timeout_ns = qemu_soonest_timeout(poll_timeout_ns, timeout);
qemu_mutex_unlock_iothread();
g_poll_ret = qemu_poll_ns(poll_fds, n_poll_fds + w->num, poll_timeout_ns);
qemu_mutex_lock_iothread();
if (g_poll_ret > 0) {
for (i = 0; i < w->num; i++) {
w->revents[i] = poll_fds[n_poll_fds + i].revents;
}
for (i = 0; i < w->num; i++) {
if (w->revents[i] && w->func[i]) {
w->func[i](w->opaque[i]);
}
}
}
if (g_main_context_check(context, max_priority, poll_fds, n_poll_fds)) {
g_main_context_dispatch(context);
}
return select_ret || g_poll_ret;
}
#endif
int main_loop_wait(int nonblocking)
{
int ret;
uint32_t timeout = UINT32_MAX;
int64_t timeout_ns;
if (nonblocking) {
timeout = 0;
}
/* poll any events */
g_array_set_size(gpollfds, 0); /* reset for new iteration */
/* XXX: separate device handlers from system ones */
#ifdef CONFIG_SLIRP
slirp_pollfds_fill(gpollfds, &timeout);
#endif
qemu_iohandler_fill(gpollfds);
if (timeout == UINT32_MAX) {
timeout_ns = -1;
} else {
timeout_ns = (uint64_t)timeout * (int64_t)(SCALE_MS);
}
timeout_ns = qemu_soonest_timeout(timeout_ns,
timerlistgroup_deadline_ns(
&main_loop_tlg));
ret = os_host_main_loop_wait(timeout_ns);
qemu_iohandler_poll(gpollfds, ret);
#ifdef CONFIG_SLIRP
slirp_pollfds_poll(gpollfds, (ret < 0));
#endif
qemu_clock_run_all_timers();
return ret;
}
/* Functions to operate on the main QEMU AioContext. */
QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque)
{
return aio_bh_new(qemu_aio_context, cb, opaque);
}
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