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tevent: Start to fix the epoll backend to support 2 fd events on the same fd correctly.
Add a utility function epoll_add_multiplex_fd() and a new flag EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX. This will be called by epoll_add_event() to merge two fde events with the same file descriptor. Signed-off-by: Jeremy Allison <jra@samba.org> Signed-off-by: Stefan Metzmacher <metze@samba.org> Reviewed-by: Stefan Metzmacher <metze@samba.org>
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@ -4,7 +4,8 @@
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main select loop and event handling - epoll implementation
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Copyright (C) Andrew Tridgell 2003-2005
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Copyright (C) Stefan Metzmacher 2005-2009
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Copyright (C) Stefan Metzmacher 2005-2013
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Copyright (C) Jeremy Allison 2013
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** NOTE! The following LGPL license applies to the tevent
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** library. This does NOT imply that all of Samba is released
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@ -48,6 +49,7 @@ struct epoll_event_context {
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#define EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT (1<<0)
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#define EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR (1<<1)
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#define EPOLL_ADDITIONAL_FD_FLAG_GOT_ERROR (1<<2)
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#define EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX (1<<3)
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#ifdef TEST_PANIC_FALLBACK
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@ -263,6 +265,99 @@ static void epoll_check_reopen(struct epoll_event_context *epoll_ev)
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epoll_ev->panic_state = NULL;
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}
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/*
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epoll cannot add the same file descriptor twice, once
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with read, once with write which is allowed by the
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tevent backend. Multiplex the existing fde, flag it
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as such so we can search for the correct fde on
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event triggering.
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*/
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static int epoll_add_multiplex_fd(struct epoll_event_context *epoll_ev,
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struct tevent_fd *add_fde)
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{
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struct epoll_event event;
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struct tevent_fd *mpx_fde;
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int ret;
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/* Find the existing fde that caused the EEXIST error. */
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for (mpx_fde = epoll_ev->ev->fd_events; mpx_fde; mpx_fde = mpx_fde->next) {
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if (mpx_fde->fd != add_fde->fd) {
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continue;
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}
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if (mpx_fde == add_fde) {
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continue;
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}
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break;
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}
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if (mpx_fde == NULL) {
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tevent_debug(epoll_ev->ev, TEVENT_DEBUG_FATAL,
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"can't find multiplex fde for fd[%d]",
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add_fde->fd);
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return -1;
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}
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if (mpx_fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX) {
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/* Logic error. Can't have more than 2 multiplexed fde's. */
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tevent_debug(epoll_ev->ev, TEVENT_DEBUG_FATAL,
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"multiplex fde for fd[%d] is already multiplexed\n",
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mpx_fde->fd);
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return -1;
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}
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/*
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* The multiplex fde must have the same fd, and also
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* already have an epoll event attached.
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*/
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if (!(mpx_fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT)) {
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/* Logic error. Can't have more than 2 multiplexed fde's. */
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tevent_debug(epoll_ev->ev, TEVENT_DEBUG_FATAL,
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"multiplex fde for fd[%d] has no event\n",
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mpx_fde->fd);
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return -1;
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}
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/* Modify the mpx_fde to add in the new flags. */
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ZERO_STRUCT(event);
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event.events = epoll_map_flags(mpx_fde->flags);
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event.events |= epoll_map_flags(add_fde->flags);
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event.data.ptr = mpx_fde;
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ret = epoll_ctl(epoll_ev->epoll_fd, EPOLL_CTL_MOD, mpx_fde->fd, &event);
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if (ret != 0 && errno == EBADF) {
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tevent_debug(epoll_ev->ev, TEVENT_DEBUG_ERROR,
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"EPOLL_CTL_MOD EBADF for "
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"add_fde[%p] mpx_fde[%p] fd[%d] - disabling\n",
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add_fde, mpx_fde, add_fde->fd);
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DLIST_REMOVE(epoll_ev->ev->fd_events, mpx_fde);
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mpx_fde->event_ctx = NULL;
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DLIST_REMOVE(epoll_ev->ev->fd_events, add_fde);
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add_fde->event_ctx = NULL;
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return 0;
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} else if (ret != 0) {
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return ret;
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}
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/*
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* Make each fde->additional_data pointers point at each other
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* so we can look them up from each other. They are now paired.
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*/
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mpx_fde->additional_data = (struct tevent_fd *)add_fde;
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add_fde->additional_data = (struct tevent_fd *)mpx_fde;
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/* Now flag both fde's as being multiplexed. */
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mpx_fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX;
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add_fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX;
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/* we need to keep the GOT_ERROR flag */
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if (mpx_fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_GOT_ERROR) {
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add_fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_GOT_ERROR;
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}
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return 0;
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}
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/*
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add the epoll event to the given fd_event
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*/
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