[ViewVC] Diff of: cvs/libev/ev

Comparing libev/ev_epoll.c (file contents):
Revision 1.35 by root, Thu Oct 23 04:56:49 2008 UTC vs.
Revision 1.80 by root, Thu Jul 11 05:41:39 2019 UTC

 /*
  * libev epoll fd activity backend
  *
- * Copyright (c) 2007,2008 Marc Alexander Lehmann <libev@schmorp.de>
+ * Copyright (c) 2007,2008,2009,2010,2011,2016,2017,2019 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,
  * 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.
+ * d) epoll doesn't work the same as select with many file descriptors
+ *    (such as files). while not critical, no other advanced interface
+ *    seems to share this (rather non-unixy) limitation.
+ * e) epoll claims to be embeddable, but in practise you never get
+ *    a ready event for the epoll fd (broken: <=2.6.26, working: >=2.6.32).
+ * f) epoll_ctl returning EPERM means the fd is always ready.
  *
  * 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.
+ * epoll_ctl syscalls for common usage patterns and handle the breakage
+ * ensuing from receiving events for closed and otherwise long gone
+ * file descriptors.
  */
 #include <sys/epoll.h>
-void inline_size
+#define EV_EMASK_EPERM 0x80
-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;
   /*
    * 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
+   * if the fd is added again, 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. */
+  /* store the generation counter in the upper 32 bits, the fd in the lower 32 bits */
+  ev.data.u64 = (uint64_t)(uint32_t)fd
+              | ((uint64_t)(uint32_t)++anfds [fd].egen << 32);
   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)))
+  if (ecb_expect_true (!epoll_ctl (backend_fd, oev && oldmask != nev ? EPOLL_CTL_MOD : EPOLL_CTL_ADD, fd, &ev)))
     return;
-  if (expect_true (errno == ENOENT))
+  if (ecb_expect_true (errno == ENOENT))
     {
       /* if ENOENT then the fd went away, so try to do the right thing */
       if (!nev)
-        return;
+        goto dec_egen;
       if (!epoll_ctl (backend_fd, EPOLL_CTL_ADD, fd, &ev))
         return;
     }
-  else if (expect_true (errno == EEXIST))
+  else if (ecb_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)
+        goto dec_egen;
-      if (oldmask == nev || !epoll_ctl (backend_fd, EPOLL_CTL_MOD, fd, &ev))
+      if (!epoll_ctl (backend_fd, EPOLL_CTL_MOD, fd, &ev))
         return;
     }
+  else if (ecb_expect_true (errno == EPERM))
+    {
+      /* EPERM means the fd is always ready, but epoll is too snobbish */
+      /* to handle it, unlike select or poll. */
+      anfds [fd].emask = EV_EMASK_EPERM;
+      /* add fd to epoll_eperms, if not already inside */
+      if (!(oldmask & EV_EMASK_EPERM))
+        {
+          array_needsize (int, epoll_eperms, epoll_epermmax, epoll_epermcnt + 1, array_needsize_noinit);
+          epoll_eperms [epoll_epermcnt++] = fd;
+        }
+      return;
+    }
+  else
+    assert (("libev: I/O watcher with invalid fd found in epoll_ctl", errno != EBADF && errno != ELOOP && errno != EINVAL));
   fd_kill (EV_A_ fd);
+dec_egen:
+  /* we didn't successfully call epoll_ctl, so decrement the generation counter again */
+  --anfds [fd].egen;
 }
 static void
 epoll_poll (EV_P_ ev_tstamp timeout)
 {
   int i;
+  int eventcnt;
+  if (ecb_expect_false (epoll_epermcnt))
+    timeout = 0.;
+  /* epoll wait times cannot be larger than (LONG_MAX - 999UL) / HZ msecs, which is below */
+  /* the default libev max wait time, however. */
+  EV_RELEASE_CB;
-  int eventcnt = epoll_wait (backend_fd, epoll_events, epoll_eventmax, (int)ceil (timeout * 1000.));
+  eventcnt = epoll_wait (backend_fd, epoll_events, epoll_eventmax, EV_TS_TO_MS (timeout));
+  EV_ACQUIRE_CB;
-  if (expect_false (eventcnt < 0))
+  if (ecb_expect_false (eventcnt < 0))
     {
       if (errno != EINTR)
-        syserr ("(libev) epoll_wait");
+        ev_syserr ("(libev) epoll_wait");
       return;
     }
   for (i = 0; i < eventcnt; ++i)
     {
       struct epoll_event *ev = epoll_events + i;
-      int fd   = ev->data.u64;
+      int fd = (uint32_t)ev->data.u64; /* mask out the lower 32 bits */
+      int want = anfds [fd].events;
       int got  = (ev->events & (EPOLLOUT | EPOLLERR | EPOLLHUP) ? EV_WRITE : 0)
                | (ev->events & (EPOLLIN  | EPOLLERR | EPOLLHUP) ? EV_READ  : 0);
-      int want = anfds [fd].events;
+      /*
+       * check for spurious notification.
+       * this only finds spurious notifications on egen updates
+       * other spurious notifications will be found by epoll_ctl, below
+       * we assume that fd is always in range, as we never shrink the anfds array
+       */
+      if (ecb_expect_false ((uint32_t)anfds [fd].egen != (uint32_t)(ev->data.u64 >> 32)))
+        {
+          /* recreate kernel state */
+          postfork |= 2;
+          continue;
+        }
-      if (expect_false (got & ~want))
+      if (ecb_expect_false (got & ~want))
         {
           anfds [fd].emask = want;
+          /*
-          /* we received an event but are not interested in it, try mod or del */
+           * 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 */
+           * this often happens because we optimistically do not unregister fds
+           * when we are no longer interested in them, but also when we get spurious
+           * notifications for fds from another process. this is partially handled
+           * above with the gencounter check (== our fd is not the event fd), and
+           * partially here, when epoll_ctl returns an error (== a child has the fd
+           * but we closed it).
+           * note: for events such as POLLHUP, where we can't know whether it refers
+           * to EV_READ or EV_WRITE, we might issue redundant EPOLL_CTL_MOD calls.
+           */
           ev->events = (want & EV_READ  ? EPOLLIN  : 0)
                      | (want & EV_WRITE ? EPOLLOUT : 0);
+          /* pre-2.6.9 kernels require a non-null pointer with EPOLL_CTL_DEL, */
+          /* which is fortunately easy to do for us. */
-          epoll_ctl (backend_fd, want ? EPOLL_CTL_MOD : EPOLL_CTL_DEL, fd, ev);
+          if (epoll_ctl (backend_fd, want ? EPOLL_CTL_MOD : EPOLL_CTL_DEL, fd, ev))
+            {
+              postfork |= 2; /* an error occurred, recreate kernel state */
+              continue;
+            }
         }
       fd_event (EV_A_ fd, got);
     }
   /* if the receive array was full, increase its size */
-  if (expect_false (eventcnt == epoll_eventmax))
+  if (ecb_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);
     }
-}
+  /* now synthesize events for all fds where epoll fails, while select works... */
+  for (i = epoll_epermcnt; i--; )
+    {
+      int fd = epoll_eperms [i];
+      unsigned char events = anfds [fd].events & (EV_READ | EV_WRITE);
+      if (anfds [fd].emask & EV_EMASK_EPERM && events)
+        fd_event (EV_A_ fd, events);
+      else
+        {
+          epoll_eperms [i] = epoll_eperms [--epoll_epermcnt];
+          anfds [fd].emask = 0;
+        }
+    }
+}
+static int
+epoll_epoll_create (void)
+{
+  int fd;
+#if defined EPOLL_CLOEXEC && !defined __ANDROID__
+  fd = epoll_create1 (EPOLL_CLOEXEC);
+  if (fd < 0 && (errno == EINVAL || errno == ENOSYS))
+#endif
+    {
+      fd = epoll_create (256);
+      if (fd >= 0)
+        fcntl (fd, F_SETFD, FD_CLOEXEC);
+    }
+  return fd;
+}
-int inline_size
+inline_size
+int
 epoll_init (EV_P_ int flags)
 {
-  backend_fd = epoll_create (256);
+  if ((backend_fd = epoll_epoll_create ()) < 0)
-  if (backend_fd < 0)
     return 0;
-  fcntl (backend_fd, F_SETFD, FD_CLOEXEC);
+  backend_mintime = 1e-3; /* epoll does sometimes return early, this is just to avoid the worst */
-  backend_fudge  = 0.; /* kernel sources seem to indicate this to be zero */
-  backend_modify = epoll_modify;
+  backend_modify  = epoll_modify;
-  backend_poll   = epoll_poll;
+  backend_poll    = epoll_poll;
-  epoll_eventmax = 64; /* intiial number of events receivable per poll */
+  epoll_eventmax = 64; /* initial 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
+inline_size
+void
 epoll_destroy (EV_P)
 {
   ev_free (epoll_events);
+  array_free (epoll_eperm, EMPTY);
 }
-void inline_size
+ecb_cold
+static void
 epoll_fork (EV_P)
 {
   close (backend_fd);
-  while ((backend_fd = epoll_create (256)) < 0)
+  while ((backend_fd = epoll_epoll_create ()) < 0)
-    syserr ("(libev) epoll_create");
+    ev_syserr ("(libev) epoll_create");
-  fcntl (backend_fd, F_SETFD, FD_CLOEXEC);
   fd_rearm_all (EV_A);
 }

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Comparing libev/ev_epoll.c (file contents): Revision 1.35 by root, Thu Oct 23 04:56:49 2008 UTC vs. Revision 1.80 by root, Thu Jul 11 05:41:39 2019 UTC

Diff Legend

Comparing libev/ev_epoll.c (file contents):
Revision 1.35 by root, Thu Oct 23 04:56:49 2008 UTC vs.
Revision 1.80 by root, Thu Jul 11 05:41:39 2019 UTC