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>

void inline_size
unsigned_char_init (unsigned char *base, int count)
{
  /* memset might be overkill */
  while (count--)
    *base++ = 0;
}

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

  /*
   * 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.
   * the fd is later added, we try to ADD it, and, if that
   * fails, we assume it still has the same eventmask.
   */
  if (!nev)
    return;

  oldmask = anfds [fd].emask;
  anfds [fd].emask = nev;

  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))
    {
      /* if ENOENT then 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))
    {
      /* EEXIST means we ignored a previous DEL, but the fd is still active */
      /* if the kernel mask is the same as the new mask, we assume it hasn't changed */
      if (oldmask == nev || !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))
        {
          anfds [fd].emask = want;

          /* we received an event but are not interested in it, try mod or del */
          /* I don't think we ever need MOD, but let's handle it anyways */
          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:	1.35
Committed:	Thu Oct 23 04:56:49 2008 UTC (15 years, 6 months ago) by root
Content type:	text/plain
Branch:	MAIN
Changes since 1.34:	+21 -3 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	void inline_size
61	unsigned_char_init (unsigned char *base, int count)
62	{
63	/* memset might be overkill */
64	while (count--)
65	*base++ = 0;
66	}
67
68	static void
69	epoll_modify (EV_P_ int fd, int oev, int nev)
70	{
71	struct epoll_event ev;
72	unsigned char oldmask;
73
74	/*
75	* we handle EPOLL_CTL_DEL by ignoring it here
76	* on the assumption that the fd is gone anyways
77	* if that is wrong, we have to handle the spurious
78	* event in epoll_poll.
79	* the fd is later added, we try to ADD it, and, if that
80	* fails, we assume it still has the same eventmask.
81	*/
82	if (!nev)
83	return;
84
85	oldmask = anfds [fd].emask;
86	anfds [fd].emask = nev;
87
88	ev.data.u64 = fd; /* use u64 to fully initialise the struct, for nicer strace etc. */
89	ev.events = (nev & EV_READ ? EPOLLIN : 0)
90	\| (nev & EV_WRITE ? EPOLLOUT : 0);
91
92	if (expect_true (!epoll_ctl (backend_fd, oev ? EPOLL_CTL_MOD : EPOLL_CTL_ADD, fd, &ev)))
93	return;
94
95	if (expect_true (errno == ENOENT))
96	{
97	/* if ENOENT then the fd went away, so try to do the right thing */
98	if (!nev)
99	return;
100
101	if (!epoll_ctl (backend_fd, EPOLL_CTL_ADD, fd, &ev))
102	return;
103	}
104	else if (expect_true (errno == EEXIST))
105	{
106	/* EEXIST means we ignored a previous DEL, but the fd is still active */
107	/* if the kernel mask is the same as the new mask, we assume it hasn't changed */
108	if (oldmask == nev \|\| !epoll_ctl (backend_fd, EPOLL_CTL_MOD, fd, &ev))
109	return;
110	}
111
112	fd_kill (EV_A_ fd);
113	}
114
115	static void
116	epoll_poll (EV_P_ ev_tstamp timeout)
117	{
118	int i;
119	int eventcnt = epoll_wait (backend_fd, epoll_events, epoll_eventmax, (int)ceil (timeout * 1000.));
120
121	if (expect_false (eventcnt < 0))
122	{
123	if (errno != EINTR)
124	syserr ("(libev) epoll_wait");
125
126	return;
127	}
128
129	for (i = 0; i < eventcnt; ++i)
130	{
131	struct epoll_event *ev = epoll_events + i;
132
133	int fd = ev->data.u64;
134	int got = (ev->events & (EPOLLOUT \| EPOLLERR \| EPOLLHUP) ? EV_WRITE : 0)
135	\| (ev->events & (EPOLLIN \| EPOLLERR \| EPOLLHUP) ? EV_READ : 0);
136	int want = anfds [fd].events;
137
138	if (expect_false (got & ~want))
139	{
140	anfds [fd].emask = want;
141
142	/* we received an event but are not interested in it, try mod or del */
143	/* I don't think we ever need MOD, but let's handle it anyways */
144	ev->events = (want & EV_READ ? EPOLLIN : 0)
145	\| (want & EV_WRITE ? EPOLLOUT : 0);
146
147	epoll_ctl (backend_fd, want ? EPOLL_CTL_MOD : EPOLL_CTL_DEL, fd, ev);
148	}
149
150	fd_event (EV_A_ fd, got);
151	}
152
153	/* if the receive array was full, increase its size */
154	if (expect_false (eventcnt == epoll_eventmax))
155	{
156	ev_free (epoll_events);
157	epoll_eventmax = array_nextsize (sizeof (struct epoll_event), epoll_eventmax, epoll_eventmax + 1);
158	epoll_events = (struct epoll_event )ev_malloc (sizeof (struct epoll_event) epoll_eventmax);
159	}
160	}
161
162	int inline_size
163	epoll_init (EV_P_ int flags)
164	{
165	backend_fd = epoll_create (256);
166
167	if (backend_fd < 0)
168	return 0;
169
170	fcntl (backend_fd, F_SETFD, FD_CLOEXEC);
171
172	backend_fudge = 0.; /* kernel sources seem to indicate this to be zero */
173	backend_modify = epoll_modify;
174	backend_poll = epoll_poll;
175
176	epoll_eventmax = 64; /* intiial number of events receivable per poll */
177	epoll_events = (struct epoll_event )ev_malloc (sizeof (struct epoll_event) epoll_eventmax);
178
179	return EVBACKEND_EPOLL;
180	}
181
182	void inline_size
183	epoll_destroy (EV_P)
184	{
185	ev_free (epoll_events);
186	}
187
188	void inline_size
189	epoll_fork (EV_P)
190	{
191	close (backend_fd);
192
193	while ((backend_fd = epoll_create (256)) < 0)
194	syserr ("(libev) epoll_create");
195
196	fcntl (backend_fd, F_SETFD, FD_CLOEXEC);
197
198	fd_rearm_all (EV_A);
199	}
200