libev/ev_epoll.c

/*
 * libev epoll fd activity backend
 *
 * Copyright (c) 2007,2008 Marc Alexander Lehmann <libev@schmorp.de>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modifica-
 * tion, 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.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
 * CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO
 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
 * CIAL, 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 OTH-
 * ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Alternatively, the contents of this file may be used under the terms of
 * the GNU General Public License ("GPL") version 2 or any later version,
 * in which case the provisions of the GPL are applicable instead of
 * the above. If you wish to allow the use of your version of this file
 * only under the terms of the GPL and not to allow others to use your
 * version of this file under the BSD license, indicate your decision
 * by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL. If you do not delete the
 * provisions above, a recipient may use your version of this file under
 * either the BSD or the GPL.
 */

/*
 * general notes about epoll:
 *
 * a) epoll silently removes fds from the fd set. as nothing tells us
 *    that an fd has been removed otherwise, we have to continually
 *    "rearm" fds that we suspect *might* have changed (same
 *    problem with kqueue, but much less costly there).
 * b) the fact that ADD != MOD creates a lot of extra syscalls due to a)
 *    and seems not to have any advantage.
 * c) the inability to handle fork or file descriptors (think dup)
 *    limits the applicability over poll, so this is not a generic
 *    poll replacement.
 *
 * lots of "weird code" and complication handling in this file is due
 * to these design problems with epoll, as we try very hard to avoid
 * epoll_ctl syscalls for common usage patterns.
 */

#include <sys/epoll.h>

static void
epoll_modify (EV_P_ int fd, int oev, int nev)
{
  struct epoll_event ev;

  /*
   * we handle EPOLL_CTL_DEL by ignoring it here
   * on the assumption that the fd is gone anyways
   * if that is wrong, we have to handle the spurious
   * event in epoll_poll.
   */
  if (!nev)
    return;

  ev.data.u64 = fd; /* use u64 to fully initialise the struct, for nicer strace etc. */
  ev.events   = (nev & EV_READ  ? EPOLLIN  : 0)
              | (nev & EV_WRITE ? EPOLLOUT : 0);

  if (expect_true (!epoll_ctl (backend_fd, oev ? EPOLL_CTL_MOD : EPOLL_CTL_ADD, fd, &ev)))
    return;

  if (expect_true (errno == ENOENT))
    {
      /* on ENOENT the fd went away, so try to do the right thing */
      if (!nev)
        return;

      if (!epoll_ctl (backend_fd, EPOLL_CTL_ADD, fd, &ev))
        return;
    }
  else if (expect_true (errno == EEXIST))
    {
      /* on EEXIST we ignored a previous DEL */
      if (!epoll_ctl (backend_fd, EPOLL_CTL_MOD, fd, &ev))
        return;
    }

  fd_kill (EV_A_ fd);
}

static void
epoll_poll (EV_P_ ev_tstamp timeout)
{
  int i;
  int eventcnt = epoll_wait (backend_fd, epoll_events, epoll_eventmax, (int)ceil (timeout * 1000.));

  if (expect_false (eventcnt < 0))
    {
      if (errno != EINTR)
        syserr ("(libev) epoll_wait");

      return;
    }

  for (i = 0; i < eventcnt; ++i)
    {
      struct epoll_event *ev = epoll_events + i;

      int fd   = ev->data.u64;
      int got  = (ev->events & (EPOLLOUT | EPOLLERR | EPOLLHUP) ? EV_WRITE : 0)
               | (ev->events & (EPOLLIN  | EPOLLERR | EPOLLHUP) ? EV_READ  : 0);
      int want = anfds [fd].events;

      if (expect_false (got & ~want))
        {
          /* we received an event but are not interested in it, try mod or del */
          ev->events = (want & EV_READ  ? EPOLLIN  : 0)
                     | (want & EV_WRITE ? EPOLLOUT : 0);

          epoll_ctl (backend_fd, want ? EPOLL_CTL_MOD : EPOLL_CTL_DEL, fd, ev);
        }

      fd_event (EV_A_ fd, got);
    }

  /* if the receive array was full, increase its size */
  if (expect_false (eventcnt == epoll_eventmax))
    {
      ev_free (epoll_events);
      epoll_eventmax = array_nextsize (sizeof (struct epoll_event), epoll_eventmax, epoll_eventmax + 1);
      epoll_events = (struct epoll_event *)ev_malloc (sizeof (struct epoll_event) * epoll_eventmax);
    }
}

int inline_size
epoll_init (EV_P_ int flags)
{
  backend_fd = epoll_create (256);

  if (backend_fd < 0)
    return 0;

  fcntl (backend_fd, F_SETFD, FD_CLOEXEC);

  backend_fudge  = 0.; /* kernel sources seem to indicate this to be zero */
  backend_modify = epoll_modify;
  backend_poll   = epoll_poll;

  epoll_eventmax = 64; /* intiial number of events receivable per poll */
  epoll_events = (struct epoll_event *)ev_malloc (sizeof (struct epoll_event) * epoll_eventmax);

  return EVBACKEND_EPOLL;
}

void inline_size
epoll_destroy (EV_P)
{
  ev_free (epoll_events);
}

void inline_size
epoll_fork (EV_P)
{
  close (backend_fd);

  while ((backend_fd = epoll_create (256)) < 0)
    syserr ("(libev) epoll_create");

  fcntl (backend_fd, F_SETFD, FD_CLOEXEC);

  fd_rearm_all (EV_A);
}

Revision:	1.34
Committed:	Fri May 23 16:37:38 2008 UTC (16 years, 4 months ago) by root
Content type:	text/plain
Branch:	MAIN
CVS Tags:	rel-3_44, rel-3_45, rel-3_41, rel-3_42, rel-3_43, rel-3_431
Changes since 1.33:	+1 -1 lines
Log Message:	* empty log message *
#	Content
1	/*
2	* libev epoll fd activity backend
3	*
4	* Copyright (c) 2007,2008 Marc Alexander Lehmann <libev@schmorp.de>
5	* All rights reserved.
6	*
7	* Redistribution and use in source and binary forms, with or without modifica-
8	* tion, are permitted provided that the following conditions are met:
9	*
10	* 1. Redistributions of source code must retain the above copyright notice,
11	* this list of conditions and the following disclaimer.
12	*
13	* 2. Redistributions in binary form must reproduce the above copyright
14	* notice, this list of conditions and the following disclaimer in the
15	* documentation and/or other materials provided with the distribution.
16	*
17	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
18	* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
19	* CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
20	* EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
21	* CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
22	* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
23	* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
24	* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
25	* ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
26	* OF THE POSSIBILITY OF SUCH DAMAGE.
27	*
28	* Alternatively, the contents of this file may be used under the terms of
29	* the GNU General Public License ("GPL") version 2 or any later version,
30	* in which case the provisions of the GPL are applicable instead of
31	* the above. If you wish to allow the use of your version of this file
32	* only under the terms of the GPL and not to allow others to use your
33	* version of this file under the BSD license, indicate your decision
34	* by deleting the provisions above and replace them with the notice
35	* and other provisions required by the GPL. If you do not delete the
36	* provisions above, a recipient may use your version of this file under
37	* either the BSD or the GPL.
38	*/
39
40	/*
41	* general notes about epoll:
42	*
43	* a) epoll silently removes fds from the fd set. as nothing tells us
44	* that an fd has been removed otherwise, we have to continually
45	* "rearm" fds that we suspect might have changed (same
46	* problem with kqueue, but much less costly there).
47	* b) the fact that ADD != MOD creates a lot of extra syscalls due to a)
48	* and seems not to have any advantage.
49	* c) the inability to handle fork or file descriptors (think dup)
50	* limits the applicability over poll, so this is not a generic
51	* poll replacement.
52	*
53	* lots of "weird code" and complication handling in this file is due
54	* to these design problems with epoll, as we try very hard to avoid
55	* epoll_ctl syscalls for common usage patterns.
56	*/
57
58	#include <sys/epoll.h>
59
60	static void
61	epoll_modify (EV_P_ int fd, int oev, int nev)
62	{
63	struct epoll_event ev;
64
65	/*
66	* we handle EPOLL_CTL_DEL by ignoring it here
67	* on the assumption that the fd is gone anyways
68	* if that is wrong, we have to handle the spurious
69	* event in epoll_poll.
70	*/
71	if (!nev)
72	return;
73
74	ev.data.u64 = fd; /* use u64 to fully initialise the struct, for nicer strace etc. */
75	ev.events = (nev & EV_READ ? EPOLLIN : 0)
76	\| (nev & EV_WRITE ? EPOLLOUT : 0);
77
78	if (expect_true (!epoll_ctl (backend_fd, oev ? EPOLL_CTL_MOD : EPOLL_CTL_ADD, fd, &ev)))
79	return;
80
81	if (expect_true (errno == ENOENT))
82	{
83	/* on ENOENT the fd went away, so try to do the right thing */
84	if (!nev)
85	return;
86
87	if (!epoll_ctl (backend_fd, EPOLL_CTL_ADD, fd, &ev))
88	return;
89	}
90	else if (expect_true (errno == EEXIST))
91	{
92	/* on EEXIST we ignored a previous DEL */
93	if (!epoll_ctl (backend_fd, EPOLL_CTL_MOD, fd, &ev))
94	return;
95	}
96
97	fd_kill (EV_A_ fd);
98	}
99
100	static void
101	epoll_poll (EV_P_ ev_tstamp timeout)
102	{
103	int i;
104	int eventcnt = epoll_wait (backend_fd, epoll_events, epoll_eventmax, (int)ceil (timeout * 1000.));
105
106	if (expect_false (eventcnt < 0))
107	{
108	if (errno != EINTR)
109	syserr ("(libev) epoll_wait");
110
111	return;
112	}
113
114	for (i = 0; i < eventcnt; ++i)
115	{
116	struct epoll_event *ev = epoll_events + i;
117
118	int fd = ev->data.u64;
119	int got = (ev->events & (EPOLLOUT \| EPOLLERR \| EPOLLHUP) ? EV_WRITE : 0)
120	\| (ev->events & (EPOLLIN \| EPOLLERR \| EPOLLHUP) ? EV_READ : 0);
121	int want = anfds [fd].events;
122
123	if (expect_false (got & ~want))
124	{
125	/* we received an event but are not interested in it, try mod or del */
126	ev->events = (want & EV_READ ? EPOLLIN : 0)
127	\| (want & EV_WRITE ? EPOLLOUT : 0);
128
129	epoll_ctl (backend_fd, want ? EPOLL_CTL_MOD : EPOLL_CTL_DEL, fd, ev);
130	}
131
132	fd_event (EV_A_ fd, got);
133	}
134
135	/* if the receive array was full, increase its size */
136	if (expect_false (eventcnt == epoll_eventmax))
137	{
138	ev_free (epoll_events);
139	epoll_eventmax = array_nextsize (sizeof (struct epoll_event), epoll_eventmax, epoll_eventmax + 1);
140	epoll_events = (struct epoll_event )ev_malloc (sizeof (struct epoll_event) epoll_eventmax);
141	}
142	}
143
144	int inline_size
145	epoll_init (EV_P_ int flags)
146	{
147	backend_fd = epoll_create (256);
148
149	if (backend_fd < 0)
150	return 0;
151
152	fcntl (backend_fd, F_SETFD, FD_CLOEXEC);
153
154	backend_fudge = 0.; /* kernel sources seem to indicate this to be zero */
155	backend_modify = epoll_modify;
156	backend_poll = epoll_poll;
157
158	epoll_eventmax = 64; /* intiial number of events receivable per poll */
159	epoll_events = (struct epoll_event )ev_malloc (sizeof (struct epoll_event) epoll_eventmax);
160
161	return EVBACKEND_EPOLL;
162	}
163
164	void inline_size
165	epoll_destroy (EV_P)
166	{
167	ev_free (epoll_events);
168	}
169
170	void inline_size
171	epoll_fork (EV_P)
172	{
173	close (backend_fd);
174
175	while ((backend_fd = epoll_create (256)) < 0)
176	syserr ("(libev) epoll_create");
177
178	fcntl (backend_fd, F_SETFD, FD_CLOEXEC);
179
180	fd_rearm_all (EV_A);
181	}
182