mirror of
https://gitlab.torproject.org/tpo/core/tor.git
synced 2024-12-06 19:41:15 +01:00
Nick Mathewson
c5a3e2ca44
We've been labeling some events as happening "outside the event loop", to avoid Libevent starvation. This patch provides a cleaner mechanism to avoid that starvation. For background, the problem here is that Libevent only scans for new events once it has run all its active callbacks. So if the callbacks keep activating new callbacks, they could potentially starve Libevent indefinitely and keep it from ever checking for timed, socket, or signal events. To solve this, we add the ability to label some events as "post-loop". The rule for a "post-loop" event is that any events _it_ activates can only be run after libevent has re-scanned for new events at least once.
100 lines
3.6 KiB
C
100 lines
3.6 KiB
C
/* Copyright (c) 2009-2017, The Tor Project, Inc. */
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/* See LICENSE for licensing information */
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#ifndef TOR_COMPAT_LIBEVENT_H
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#define TOR_COMPAT_LIBEVENT_H
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#include "orconfig.h"
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#include "testsupport.h"
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void configure_libevent_logging(void);
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void suppress_libevent_log_msg(const char *msg);
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#define tor_event_new event_new
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#define tor_evtimer_new evtimer_new
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#define tor_evsignal_new evsignal_new
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#define tor_evdns_add_server_port(sock, tcp, cb, data) \
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evdns_add_server_port_with_base(tor_libevent_get_base(), \
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(sock),(tcp),(cb),(data));
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struct event;
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struct event_base;
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void tor_event_free_(struct event *ev);
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#define tor_event_free(ev) \
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FREE_AND_NULL(struct event, tor_event_free_, (ev))
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typedef struct periodic_timer_t periodic_timer_t;
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periodic_timer_t *periodic_timer_new(struct event_base *base,
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const struct timeval *tv,
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void (*cb)(periodic_timer_t *timer, void *data),
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void *data);
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void periodic_timer_free_(periodic_timer_t *);
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#define periodic_timer_free(t) \
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FREE_AND_NULL(periodic_timer_t, periodic_timer_free_, (t))
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typedef struct mainloop_event_t mainloop_event_t;
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mainloop_event_t *mainloop_event_new(void (*cb)(mainloop_event_t *, void *),
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void *userdata);
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mainloop_event_t * mainloop_event_postloop_new(
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void (*cb)(mainloop_event_t *, void *),
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void *userdata);
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void mainloop_event_activate(mainloop_event_t *event);
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int mainloop_event_schedule(mainloop_event_t *event,
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const struct timeval *delay);
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void mainloop_event_cancel(mainloop_event_t *event);
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void mainloop_event_free_(mainloop_event_t *event);
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#define mainloop_event_free(event) \
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FREE_AND_NULL(mainloop_event_t, mainloop_event_free_, (event))
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/** Defines a configuration for using libevent with Tor: passed as an argument
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* to tor_libevent_initialize() to describe how we want to set up. */
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typedef struct tor_libevent_cfg {
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/** How many CPUs should we use (not currently useful). */
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int num_cpus;
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/** How many milliseconds should we allow between updating bandwidth limits?
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* (Not currently useful). */
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int msec_per_tick;
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} tor_libevent_cfg;
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void tor_libevent_initialize(tor_libevent_cfg *cfg);
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MOCK_DECL(struct event_base *, tor_libevent_get_base, (void));
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const char *tor_libevent_get_method(void);
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void tor_check_libevent_header_compatibility(void);
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const char *tor_libevent_get_version_str(void);
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const char *tor_libevent_get_header_version_str(void);
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void tor_libevent_free_all(void);
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int tor_init_libevent_rng(void);
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void tor_gettimeofday_cached(struct timeval *tv);
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void tor_gettimeofday_cache_clear(void);
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#ifdef TOR_UNIT_TESTS
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void tor_gettimeofday_cache_set(const struct timeval *tv);
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void tor_libevent_postfork(void);
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#endif
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int tor_libevent_run_event_loop(struct event_base *base, int once);
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void tor_libevent_exit_loop_after_delay(struct event_base *base,
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const struct timeval *delay);
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void tor_libevent_exit_loop_after_callback(struct event_base *base);
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#ifdef COMPAT_LIBEVENT_PRIVATE
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/** Macro: returns the number of a Libevent version as a 4-byte number,
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with the first three bytes representing the major, minor, and patchlevel
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respectively of the library. The fourth byte is unused.
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This is equivalent to the format of LIBEVENT_VERSION_NUMBER on Libevent
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2.0.1 or later. */
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#define V(major, minor, patch) \
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(((major) << 24) | ((minor) << 16) | ((patch) << 8))
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STATIC void
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libevent_logging_callback(int severity, const char *msg);
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#endif /* defined(COMPAT_LIBEVENT_PRIVATE) */
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#endif /* !defined(TOR_COMPAT_LIBEVENT_H) */
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