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c0e425abdc
Back when deferred_cb stuff had its own queue, the queue was always executed, but we never ran more than 16 callbacks per iteration. That made for two problems: 1: Because deferred_cb stuff would always run, and had no priority, it could cause priority inversion. 2: It doesn't respect the max_dispatch_interval code. Then, when I refactored deferred_cb to be a special case of event_callback, that solved the above issues, but made for two more issues: 3: Because deferred_cb stuff would always get the default priority, it could could low-priority bufferevents to get too much priority. 4: With code like bufferevent_pair, it's easy to get into a situation where two deferreds keep adding one another, preventing the event loop from ever actually scanning for more events. This commit fixes the above by giving deferreds a better notion of priorities, and by limiting the number of deferreds that can be added to the _current_ loop iteration's active queues. (Extra deferreds are put into the active_later state.) That isn't an all-purpose priority inversion solution, of course: for that, you may need to mess around with max_dispatch_interval.
71 lines
2.7 KiB
C
71 lines
2.7 KiB
C
/*
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* Copyright (c) 2009-2012 Niels Provos and Nick Mathewson
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef DEFER_INTERNAL_H_INCLUDED_
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#define DEFER_INTERNAL_H_INCLUDED_
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#ifdef __cplusplus
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extern "C" {
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#endif
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#include "event2/event-config.h"
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#include "evconfig-private.h"
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#include <sys/queue.h>
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struct event_callback;
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typedef void (*deferred_cb_fn)(struct event_callback *, void *);
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/**
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Initialize an empty, non-pending event_callback.
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@param deferred The struct event_callback structure to initialize.
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@param priority The priority that the callback should run at.
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@param cb The function to run when the struct event_callback executes.
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@param arg The function's second argument.
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*/
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void event_deferred_cb_init_(struct event_callback *, ev_uint8_t, deferred_cb_fn, void *);
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/**
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Change the priority of a non-pending event_callback.
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*/
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void event_deferred_cb_set_priority_(struct event_callback *, ev_uint8_t);
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/**
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Cancel a struct event_callback if it is currently scheduled in an event_base.
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*/
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void event_deferred_cb_cancel_(struct event_base *, struct event_callback *);
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/**
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Activate a struct event_callback if it is not currently scheduled in an event_base.
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Return true iff it was not previously scheduled.
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*/
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int event_deferred_cb_schedule_(struct event_base *, struct event_callback *);
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#ifdef __cplusplus
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}
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#endif
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#endif /* EVENT_INTERNAL_H_INCLUDED_ */
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