tor-browser

epoll.c (14881B)

---

/*
* Copyright 2000-2007 Niels Provos <provos@citi.umich.edu>
* Copyright 2007-2012 Niels Provos, Nick Mathewson
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
*    derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "event2/event-config.h"
#include "evconfig-private.h"

#ifdef EVENT__HAVE_EPOLL

#include <stdint.h>
#include <sys/types.h>
#include <sys/resource.h>
#ifdef EVENT__HAVE_SYS_TIME_H
#include <sys/time.h>
#endif
#include <sys/queue.h>
#include <sys/epoll.h>
#include <signal.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#ifdef EVENT__HAVE_FCNTL_H
#include <fcntl.h>
#endif
#ifdef EVENT__HAVE_SYS_TIMERFD_H
#include <sys/timerfd.h>
#endif

#include "event-internal.h"
#include "evsignal-internal.h"
#include "event2/thread.h"
#include "evthread-internal.h"
#include "log-internal.h"
#include "evmap-internal.h"
#include "changelist-internal.h"
#include "time-internal.h"

/* Since Linux 2.6.17, epoll is able to report about peer half-closed connection
  using special EPOLLRDHUP flag on a read event.
*/
#if !defined(EPOLLRDHUP)
#define EPOLLRDHUP 0
#define EARLY_CLOSE_IF_HAVE_RDHUP 0
#else
#define EARLY_CLOSE_IF_HAVE_RDHUP EV_FEATURE_EARLY_CLOSE
#endif

#include "epolltable-internal.h"

#if defined(EVENT__HAVE_SYS_TIMERFD_H) &&			  \
defined(EVENT__HAVE_TIMERFD_CREATE) &&			  \
defined(HAVE_POSIX_MONOTONIC) && defined(TFD_NONBLOCK) && \
defined(TFD_CLOEXEC)
/* Note that we only use timerfd if TFD_NONBLOCK and TFD_CLOEXEC are available
  and working.  This means that we can't support it on 2.6.25 (where timerfd
  was introduced) or 2.6.26, since 2.6.27 introduced those flags.
*/
#define USING_TIMERFD
#endif

struct epollop {
struct epoll_event *events;
int nevents;
int epfd;
#ifdef USING_TIMERFD
int timerfd;
#endif
};

static void *epoll_init(struct event_base *);
static int epoll_dispatch(struct event_base *, struct timeval *);
static void epoll_dealloc(struct event_base *);

static const struct eventop epollops_changelist = {
"epoll (with changelist)",
epoll_init,
event_changelist_add_,
event_changelist_del_,
epoll_dispatch,
epoll_dealloc,
1, /* need reinit */
EV_FEATURE_ET|EV_FEATURE_O1| EARLY_CLOSE_IF_HAVE_RDHUP,
EVENT_CHANGELIST_FDINFO_SIZE
};


static int epoll_nochangelist_add(struct event_base *base, evutil_socket_t fd,
   short old, short events, void *p);
static int epoll_nochangelist_del(struct event_base *base, evutil_socket_t fd,
   short old, short events, void *p);

const struct eventop epollops = {
"epoll",
epoll_init,
epoll_nochangelist_add,
epoll_nochangelist_del,
epoll_dispatch,
epoll_dealloc,
1, /* need reinit */
EV_FEATURE_ET|EV_FEATURE_O1|EV_FEATURE_EARLY_CLOSE,
0
};

#define INITIAL_NEVENT 32
#define MAX_NEVENT 4096

/* On Linux kernels at least up to 2.6.24.4, epoll can't handle timeout
* values bigger than (LONG_MAX - 999ULL)/HZ.  HZ in the wild can be
* as big as 1000, and LONG_MAX can be as small as (1<<31)-1, so the
* largest number of msec we can support here is 2147482.  Let's
* round that down by 47 seconds.
*/
#define MAX_EPOLL_TIMEOUT_MSEC (35*60*1000)

static void *
epoll_init(struct event_base *base)
{
int epfd = -1;
struct epollop *epollop;

#ifdef EVENT__HAVE_EPOLL_CREATE1
/* First, try the shiny new epoll_create1 interface, if we have it. */
epfd = epoll_create1(EPOLL_CLOEXEC);
#endif
if (epfd == -1) {
	/* Initialize the kernel queue using the old interface.  (The
	size field is ignored   since 2.6.8.) */
	if ((epfd = epoll_create(32000)) == -1) {
		if (errno != ENOSYS)
			event_warn("epoll_create");
		return (NULL);
	}
	evutil_make_socket_closeonexec(epfd);
}

if (!(epollop = mm_calloc(1, sizeof(struct epollop)))) {
	close(epfd);
	return (NULL);
}

epollop->epfd = epfd;

/* Initialize fields */
epollop->events = mm_calloc(INITIAL_NEVENT, sizeof(struct epoll_event));
if (epollop->events == NULL) {
	mm_free(epollop);
	close(epfd);
	return (NULL);
}
epollop->nevents = INITIAL_NEVENT;

if ((base->flags & EVENT_BASE_FLAG_EPOLL_USE_CHANGELIST) != 0 ||
    ((base->flags & EVENT_BASE_FLAG_IGNORE_ENV) == 0 &&
	evutil_getenv_("EVENT_EPOLL_USE_CHANGELIST") != NULL)) {

	base->evsel = &epollops_changelist;
}

#ifdef USING_TIMERFD
/*
  The epoll interface ordinarily gives us one-millisecond precision,
  so on Linux it makes perfect sense to use the CLOCK_MONOTONIC_COARSE
  timer.  But when the user has set the new PRECISE_TIMER flag for an
  event_base, we can try to use timerfd to give them finer granularity.
*/
if ((base->flags & EVENT_BASE_FLAG_PRECISE_TIMER) &&
    base->monotonic_timer.monotonic_clock == CLOCK_MONOTONIC) {
	int fd;
	fd = epollop->timerfd = timerfd_create(CLOCK_MONOTONIC, TFD_NONBLOCK|TFD_CLOEXEC);
	if (epollop->timerfd >= 0) {
		struct epoll_event epev;
		memset(&epev, 0, sizeof(epev));
		epev.data.fd = epollop->timerfd;
		epev.events = EPOLLIN;
		if (epoll_ctl(epollop->epfd, EPOLL_CTL_ADD, fd, &epev) < 0) {
			event_warn("epoll_ctl(timerfd)");
			close(fd);
			epollop->timerfd = -1;
		}
	} else {
		if (errno != EINVAL && errno != ENOSYS) {
			/* These errors probably mean that we were
			 * compiled with timerfd/TFD_* support, but
			 * we're running on a kernel that lacks those.
			 */
			event_warn("timerfd_create");
		}
		epollop->timerfd = -1;
	}
} else {
	epollop->timerfd = -1;
}
#endif

evsig_init_(base);

return (epollop);
}

static const char *
change_to_string(int change)
{
change &= (EV_CHANGE_ADD|EV_CHANGE_DEL);
if (change == EV_CHANGE_ADD) {
	return "add";
} else if (change == EV_CHANGE_DEL) {
	return "del";
} else if (change == 0) {
	return "none";
} else {
	return "???";
}
}

static const char *
epoll_op_to_string(int op)
{
return op == EPOLL_CTL_ADD?"ADD":
    op == EPOLL_CTL_DEL?"DEL":
    op == EPOLL_CTL_MOD?"MOD":
    "???";
}

#define PRINT_CHANGES(op, events, ch, status)  \
"Epoll %s(%d) on fd %d " status ". "       \
"Old events were %d; "                     \
"read change was %d (%s); "                \
"write change was %d (%s); "               \
"close change was %d (%s)",                \
epoll_op_to_string(op),                    \
events,                                    \
ch->fd,                                    \
ch->old_events,                            \
ch->read_change,                           \
change_to_string(ch->read_change),         \
ch->write_change,                          \
change_to_string(ch->write_change),        \
ch->close_change,                          \
change_to_string(ch->close_change)

static int
epoll_apply_one_change(struct event_base *base,
   struct epollop *epollop,
   const struct event_change *ch)
{
struct epoll_event epev;
int op, events = 0;
int idx;

idx = EPOLL_OP_TABLE_INDEX(ch);
op = epoll_op_table[idx].op;
events = epoll_op_table[idx].events;

if (!events) {
	EVUTIL_ASSERT(op == 0);
	return 0;
}

if ((ch->read_change|ch->write_change|ch->close_change) & EV_CHANGE_ET)
	events |= EPOLLET;

memset(&epev, 0, sizeof(epev));
epev.data.fd = ch->fd;
epev.events = events;
if (epoll_ctl(epollop->epfd, op, ch->fd, &epev) == 0) {
	event_debug((PRINT_CHANGES(op, epev.events, ch, "okay")));
	return 0;
}

switch (op) {
case EPOLL_CTL_MOD:
	if (errno == ENOENT) {
		/* If a MOD operation fails with ENOENT, the
		 * fd was probably closed and re-opened.  We
		 * should retry the operation as an ADD.
		 */
		if (epoll_ctl(epollop->epfd, EPOLL_CTL_ADD, ch->fd, &epev) == -1) {
			event_warn("Epoll MOD(%d) on %d retried as ADD; that failed too",
			    (int)epev.events, ch->fd);
			return -1;
		} else {
			event_debug(("Epoll MOD(%d) on %d retried as ADD; succeeded.",
				(int)epev.events,
				ch->fd));
			return 0;
		}
	}
	break;
case EPOLL_CTL_ADD:
	if (errno == EEXIST) {
		/* If an ADD operation fails with EEXIST,
		 * either the operation was redundant (as with a
		 * precautionary add), or we ran into a fun
		 * kernel bug where using dup*() to duplicate the
		 * same file into the same fd gives you the same epitem
		 * rather than a fresh one.  For the second case,
		 * we must retry with MOD. */
		if (epoll_ctl(epollop->epfd, EPOLL_CTL_MOD, ch->fd, &epev) == -1) {
			event_warn("Epoll ADD(%d) on %d retried as MOD; that failed too",
			    (int)epev.events, ch->fd);
			return -1;
		} else {
			event_debug(("Epoll ADD(%d) on %d retried as MOD; succeeded.",
				(int)epev.events,
				ch->fd));
			return 0;
		}
	}
	break;
case EPOLL_CTL_DEL:
	if (errno == ENOENT || errno == EBADF || errno == EPERM) {
		/* If a delete fails with one of these errors,
		 * that's fine too: we closed the fd before we
		 * got around to calling epoll_dispatch. */
		event_debug(("Epoll DEL(%d) on fd %d gave %s: DEL was unnecessary.",
			(int)epev.events,
			ch->fd,
			strerror(errno)));
		return 0;
	}
	break;
default:
	break;
}

event_warn(PRINT_CHANGES(op, epev.events, ch, "failed"));
return -1;
}

static int
epoll_apply_changes(struct event_base *base)
{
struct event_changelist *changelist = &base->changelist;
struct epollop *epollop = base->evbase;
struct event_change *ch;

int r = 0;
int i;

for (i = 0; i < changelist->n_changes; ++i) {
	ch = &changelist->changes[i];
	if (epoll_apply_one_change(base, epollop, ch) < 0)
		r = -1;
}

return (r);
}

static int
epoll_nochangelist_add(struct event_base *base, evutil_socket_t fd,
   short old, short events, void *p)
{
struct event_change ch;
ch.fd = fd;
ch.old_events = old;
ch.read_change = ch.write_change = ch.close_change = 0;
if (events & EV_WRITE)
	ch.write_change = EV_CHANGE_ADD |
	    (events & EV_ET);
if (events & EV_READ)
	ch.read_change = EV_CHANGE_ADD |
	    (events & EV_ET);
if (events & EV_CLOSED)
	ch.close_change = EV_CHANGE_ADD |
	    (events & EV_ET);

return epoll_apply_one_change(base, base->evbase, &ch);
}

static int
epoll_nochangelist_del(struct event_base *base, evutil_socket_t fd,
   short old, short events, void *p)
{
struct event_change ch;
ch.fd = fd;
ch.old_events = old;
ch.read_change = ch.write_change = ch.close_change = 0;
if (events & EV_WRITE)
	ch.write_change = EV_CHANGE_DEL |
	    (events & EV_ET);
if (events & EV_READ)
	ch.read_change = EV_CHANGE_DEL |
	    (events & EV_ET);
if (events & EV_CLOSED)
	ch.close_change = EV_CHANGE_DEL |
	    (events & EV_ET);

return epoll_apply_one_change(base, base->evbase, &ch);
}

static int
epoll_dispatch(struct event_base *base, struct timeval *tv)
{
struct epollop *epollop = base->evbase;
struct epoll_event *events = epollop->events;
int i, res;
long timeout = -1;

#ifdef USING_TIMERFD
if (epollop->timerfd >= 0) {
	struct itimerspec is;
	is.it_interval.tv_sec = 0;
	is.it_interval.tv_nsec = 0;
	if (tv == NULL) {
		/* No timeout; disarm the timer. */
		is.it_value.tv_sec = 0;
		is.it_value.tv_nsec = 0;
	} else {
		if (tv->tv_sec == 0 && tv->tv_usec == 0) {
			/* we need to exit immediately; timerfd can't
			 * do that. */
			timeout = 0;
		}
		is.it_value.tv_sec = tv->tv_sec;
		is.it_value.tv_nsec = tv->tv_usec * 1000;
	}
	/* TODO: we could avoid unnecessary syscalls here by only
	   calling timerfd_settime when the top timeout changes, or
	   when we're called with a different timeval.
	*/
	if (timerfd_settime(epollop->timerfd, 0, &is, NULL) < 0) {
		event_warn("timerfd_settime");
	}
} else
#endif
if (tv != NULL) {
	timeout = evutil_tv_to_msec_(tv);
	if (timeout < 0 || timeout > MAX_EPOLL_TIMEOUT_MSEC) {
		/* Linux kernels can wait forever if the timeout is
		 * too big; see comment on MAX_EPOLL_TIMEOUT_MSEC. */
		timeout = MAX_EPOLL_TIMEOUT_MSEC;
	}
}

epoll_apply_changes(base);
event_changelist_remove_all_(&base->changelist, base);

EVBASE_RELEASE_LOCK(base, th_base_lock);

res = epoll_wait(epollop->epfd, events, epollop->nevents, timeout);

EVBASE_ACQUIRE_LOCK(base, th_base_lock);

if (res == -1) {
	if (errno != EINTR) {
		event_warn("epoll_wait");
		return (-1);
	}

	return (0);
}

event_debug(("%s: epoll_wait reports %d", __func__, res));
EVUTIL_ASSERT(res <= epollop->nevents);

for (i = 0; i < res; i++) {
	int what = events[i].events;
	short ev = 0;
#ifdef USING_TIMERFD
	if (events[i].data.fd == epollop->timerfd)
		continue;
#endif

	if (what & EPOLLERR) {
		ev = EV_READ | EV_WRITE;
	} else if ((what & EPOLLHUP) && !(what & EPOLLRDHUP)) {
		ev = EV_READ | EV_WRITE;
	} else {
		if (what & EPOLLIN)
			ev |= EV_READ;
		if (what & EPOLLOUT)
			ev |= EV_WRITE;
		if (what & EPOLLRDHUP)
			ev |= EV_CLOSED;
	}

	if (!ev)
		continue;

	evmap_io_active_(base, events[i].data.fd, ev | EV_ET);
}

if (res == epollop->nevents && epollop->nevents < MAX_NEVENT) {
	/* We used all of the event space this time.  We should
	   be ready for more events next time. */
	int new_nevents = epollop->nevents * 2;
	struct epoll_event *new_events;

	new_events = mm_realloc(epollop->events,
	    new_nevents * sizeof(struct epoll_event));
	if (new_events) {
		epollop->events = new_events;
		epollop->nevents = new_nevents;
	}
}

return (0);
}


static void
epoll_dealloc(struct event_base *base)
{
struct epollop *epollop = base->evbase;

evsig_dealloc_(base);
if (epollop->events)
	mm_free(epollop->events);
if (epollop->epfd >= 0)
	close(epollop->epfd);
#ifdef USING_TIMERFD
if (epollop->timerfd >= 0)
	close(epollop->timerfd);
#endif

memset(epollop, 0, sizeof(struct epollop));
mm_free(epollop);
}

#endif /* EVENT__HAVE_EPOLL */