[ViewVC] Diff of: cvs/libev/ev

Comparing libev/ev_epoll.c (file contents):
Revision 1.47 by root, Sun Jul 19 04:11:27 2009 UTC vs.
Revision 1.57 by root, Sat Jan 8 10:25:16 2011 UTC

 /*
  * libev epoll fd activity backend
  *
- * Copyright (c) 2007,2008,2009 Marc Alexander Lehmann <libev@schmorp.de>
+ * Copyright (c) 2007,2008,2009,2010,2011 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:
  *
  * 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 and handle the breakage
  * ensuing from receiving events for closed and otherwise long gone
  * file descriptors.
  */
 #include <sys/epoll.h>
+#define EV_EMASK_EPERM 0x80
 static void
 epoll_modify (EV_P_ int fd, int oev, int nev)
 {
   struct epoll_event ev;
   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 (expect_true (!epoll_ctl (backend_fd, oev && oldmask != nev ? 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 */
         goto dec_egen;
       if (!epoll_ctl (backend_fd, EPOLL_CTL_MOD, fd, &ev))
         return;
     }
+  else if (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, EMPTY2);
+          epoll_eperms [epoll_epermcnt++] = fd;
+        }
+      return;
+    }
   fd_kill (EV_A_ fd);
 dec_egen:
   /* we didn't successfully call epoll_ctl, so decrement the generation counter again */
 epoll_poll (EV_P_ ev_tstamp timeout)
 {
   int i;
   int eventcnt;
+  /* 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;
   eventcnt = epoll_wait (backend_fd, epoll_events, epoll_eventmax, (int)ceil (timeout * 1000.));
   EV_ACQUIRE_CB;
   if (expect_false (eventcnt < 0))
       int want = anfds [fd].events;
       int got  = (ev->events & (EPOLLOUT | EPOLLERR | EPOLLHUP) ? EV_WRITE : 0)
                | (ev->events & (EPOLLIN  | EPOLLERR | EPOLLHUP) ? EV_READ  : 0);
       /* check for spurious notification */
+      /* we assume that fd is always in range, as we never shrink the anfds array */
       if (expect_false ((uint32_t)anfds [fd].egen != (uint32_t)(ev->data.u64 >> 32)))
         {
           /* recreate kernel state */
           postfork = 1;
           continue;
           /* 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);
+          /* pre-2.6.9 kernels require a non-null pointer with EPOLL_CTL_DEL, */
+          /* which is fortunately easy to do for us. */
           if (epoll_ctl (backend_fd, want ? EPOLL_CTL_MOD : EPOLL_CTL_DEL, fd, ev))
             {
-              postfork = 1; /* an error occured, recreate kernel state */
+              postfork = 1; /* an error occurred, recreate kernel state */
               continue;
             }
         }
       fd_event (EV_A_ fd, got);
     {
       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];
+    }
 }
 int inline_size
 epoll_init (EV_P_ int flags)
 {
 void inline_size
 epoll_destroy (EV_P)
 {
   ev_free (epoll_events);
+  array_free (epoll_eperm, EMPTY);
 }
 void inline_size
 epoll_fork (EV_P)
 {

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Comparing libev/ev_epoll.c (file contents): Revision 1.47 by root, Sun Jul 19 04:11:27 2009 UTC vs. Revision 1.57 by root, Sat Jan 8 10:25:16 2011 UTC

Diff Legend

Comparing libev/ev_epoll.c (file contents):
Revision 1.47 by root, Sun Jul 19 04:11:27 2009 UTC vs.
Revision 1.57 by root, Sat Jan 8 10:25:16 2011 UTC