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/*
* libev epoll fd activity backend
*
* Copyright (c) 2007 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);
}
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