*** empty log message ***

[software/libev.git] / ev_epoll.c

diff --git a/ev_epoll.c b/ev_epoll.c
index 38fd3040c35418d9495233c659e951fe4d59092c..76645ec3ef126c11159930c9347aaf0b069984b7 100644 (file)
--- a/ev_epoll.c
+++ b/ev_epoll.c
@@ -4,29 +4,55 @@
  * Copyright (c) 2007 Marc Alexander Lehmann <libev@schmorp.de>
  * All rights reserved.
  *
  * 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>
  */
 
 #include <sys/epoll.h>


@@ -34,18 +60,41 @@
 static void
 epoll_modify (EV_P_ int fd, int oev, int nev)
 {
 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;
   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.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 (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
 }
 
 static void


@@ -54,7 +103,7 @@ epoll_poll (EV_P_ ev_tstamp timeout)
   int i;
   int eventcnt = epoll_wait (backend_fd, epoll_events, epoll_eventmax, (int)ceil (timeout * 1000.));
 
   int i;
   int eventcnt = epoll_wait (backend_fd, epoll_events, epoll_eventmax, (int)ceil (timeout * 1000.));
 

-  if (eventcnt < 0)
+  if (expect_false (eventcnt < 0))

     {
       if (errno != EINTR)
         syserr ("(libev) epoll_wait");
     {
       if (errno != EINTR)
         syserr ("(libev) epoll_wait");


@@ -63,12 +112,25 @@ epoll_poll (EV_P_ ev_tstamp timeout)
     }
 
   for (i = 0; i < eventcnt; ++i)
     }
 
   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))
 
   /* if the receive array was full, increase its size */
   if (expect_false (eventcnt == epoll_eventmax))


@@ -89,7 +151,7 @@ epoll_init (EV_P_ int flags)
 
   fcntl (backend_fd, F_SETFD, FD_CLOEXEC);
 
 
   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;
 
   backend_modify = epoll_modify;
   backend_poll   = epoll_poll;