* Copyright (c) 2007 Marc Alexander Lehmann <libev@schmorp.de>
* All rights reserved.
*
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are
- * met:
+ * 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.
*
- * * Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
+ * 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:
*
- * * 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.
+ * 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.
*
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "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 COPYRIGHT
- * OWNER OR CONTRIBUTORS 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.
+ * 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)
{
- int mode = nev ? oev ? EPOLL_CTL_MOD : EPOLL_CTL_ADD : EPOLL_CTL_DEL;
-
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_false (epoll_ctl (backend_fd, mode, fd, &ev)))
- if (errno != ENOENT /* on ENOENT the fd went away, so try to do the right thing */
- || (nev && epoll_ctl (backend_fd, EPOLL_CTL_ADD, fd, &ev)))
- fd_kill (EV_A_ fd);
+ 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
}
for (i = 0; i < eventcnt; ++i)
- fd_event (
- EV_A_
- epoll_events [i].data.u64,
- (epoll_events [i].events & (EPOLLOUT | EPOLLERR | EPOLLHUP) ? EV_WRITE : 0)
- | (epoll_events [i].events & (EPOLLIN | EPOLLERR | EPOLLHUP) ? EV_READ : 0)
- );
+ {
+ 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))
fcntl (backend_fd, F_SETFD, FD_CLOEXEC);
- backend_fudge = 1e-3; /* needed to compensate for epoll returning early */
+ backend_fudge = 0.; /* kernel sources seem to indicate this to be zero */
backend_modify = epoll_modify;
backend_poll = epoll_poll;
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