Branch
Hash :
2f184f8b
Author :
Date :
2019-03-26T13:33:57
evwatch: Add "prepare" and "check" watchers. Adds two new callbacks: "prepare" watchers, which fire immediately before we poll for I/O, and "check" watchers, which fire immediately after we finish polling and before we process events. This allows other event loops to be embedded into libevent's, and enables certain performance monitoring. Closes: #710
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/*
* Redistribution and use in source and binary forms, with or without
* modification, 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.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <stdlib.h>
#ifdef EVENT__HAVE_SYS_TIME_H
#include <sys/time.h>
#endif
#include <time.h>
#include "event2/event.h"
#include "event2/watch.h"
#include "regress.h"
static int iteration = 0;
static int prepare_callback_1_count = 0;
static int prepare_callback_2_count = 0;
static int check_callback_1_count = 0;
static int check_callback_2_count = 0;
static struct timeval start_time = { 0, 0 };
static struct timeval end_time = { 0, 0 };
static int user_arg = 8675309;
static void
prepare_callback_1(struct evwatch *watcher, const struct evwatch_prepare_cb_info *info, void *arg)
{
struct timeval timeout;
int timeout_msec;
/* user argument should be passed properly */
tt_ptr_op(arg, ==, &user_arg);
++prepare_callback_1_count;
/* prepare_callback_1 should always fire before prepare_callback_2, and
* before both check callbacks */
tt_int_op(prepare_callback_1_count, >, prepare_callback_2_count);
tt_int_op(prepare_callback_1_count, >, check_callback_1_count);
tt_int_op(prepare_callback_1_count, >, check_callback_2_count);
/* if we've just scheduled the timeout event at the beginning of the
* iteration, save the current time and assert that the timeout is
* roughly what we set (this won't be exact on some platforms) */
if (start_time.tv_sec == 0) {
event_base_gettimeofday_cached(evwatch_base(watcher), &start_time);
tt_int_op(evwatch_prepare_get_timeout(info, &timeout), ==, 1);
timeout_msec = (timeout.tv_sec * 1000) + (timeout.tv_usec / 1000);
tt_int_op(timeout_msec, >=, 995);
tt_int_op(timeout_msec, <=, 1005);
}
end:
;
}
static void
prepare_callback_2(struct evwatch *watcher, const struct evwatch_prepare_cb_info *info, void *arg)
{
/* user argument should be passed properly */
tt_ptr_op(arg, ==, &user_arg);
++prepare_callback_2_count;
/* prepare_callback_2 should only fire on the first iteration, and
* should fire before both check callbacks */
tt_int_op(iteration, ==, 0);
tt_int_op(prepare_callback_2_count, >, check_callback_1_count);
tt_int_op(prepare_callback_2_count, >, check_callback_2_count);
end:
;
}
static void
check_callback_1(struct evwatch *watcher, const struct evwatch_check_cb_info *info, void *arg)
{
/* user argument should be passed properly */
tt_ptr_op(arg, ==, &user_arg);
++check_callback_1_count;
/* check_callback_1 should always fire before check_callback_2 */
tt_int_op(check_callback_1_count, >, check_callback_2_count);
/* save the end time, in case the timeout fires this time through the
* event loop */
event_base_gettimeofday_cached(evwatch_base(watcher), &end_time);
end:
;
}
static void
check_callback_2(struct evwatch *watcher, const struct evwatch_check_cb_info *info, void *arg)
{
/* user argument should be passed properly */
tt_ptr_op(arg, ==, &user_arg);
++check_callback_2_count;
/* check_callback_2 should only fire on the first iteration */
tt_int_op(iteration, ==, 0);
end:
;
}
static void
timeout_callback(evutil_socket_t fd, short events, void *arg)
{
/* the duration between the start and end times should be at least 1
* second */
tt_int_op(end_time.tv_sec, >=, start_time.tv_sec + 1);
end:
;
}
/**
This tests a few important properties of "prepare" and "check" watchers:
- Watchers should be called in the order they were registered.
- Prepare watchers should be called before check watchers.
- Freeing a watcher will stop callbacks to it, but not to other watchers.
- Reported durations should align with the registered timeouts.
- It should be possible to call back into libevent from a callback without a
recursive lock.
- If this test is compiled with ASAN or similar, this test also illustrates
that event_base_free will free any watchers not previously freed by
evwatch_free.
*/
static void
test_callback_ordering(void *ptr)
{
struct basic_test_data *data = ptr;
struct event_base *base = data->base;
struct evwatch *prepare_callback_2_watcher;
struct evwatch *check_callback_2_watcher;
struct timeval timeout;
/* install prepare and check watchers */
evwatch_prepare_new(base, &prepare_callback_1, &user_arg);
evwatch_check_new(base, &check_callback_1, &user_arg);
prepare_callback_2_watcher = evwatch_prepare_new(base, &prepare_callback_2, &user_arg);
check_callback_2_watcher = evwatch_check_new(base, &check_callback_2, &user_arg);
/* schedule an 1 second timeout event, and run the event loop until the
* timeout fires */
timeout.tv_sec = 1;
timeout.tv_usec = 0;
event_base_once(base, -1, EV_TIMEOUT, &timeout_callback, 0, &timeout);
event_base_dispatch(base);
/* second iteration: free two of the watchers, schedule a timeout and
* run the event loop again */
iteration = 1;
start_time.tv_sec = 0;
evwatch_free(prepare_callback_2_watcher);
evwatch_free(check_callback_2_watcher);
event_base_once(base, -1, EV_TIMEOUT, &timeout_callback, 0, &timeout);
event_base_dispatch(base);
}
static void
prepare_callback_3(struct evwatch *watcher, const struct evwatch_prepare_cb_info *info, void *arg)
{
/* timeout should not be written to */
struct timeval timeout = { 123, 456 };
tt_int_op(evwatch_prepare_get_timeout(info, &timeout), ==, 0);
tt_int_op(timeout.tv_sec, ==, 123);
tt_int_op(timeout.tv_usec, ==, 456);
end:
;
}
/**
Test that evwatch_prepare_get_timeout behaves correctly when there is no
timeout.
*/
static void
test_timeout_unavailable(void *ptr)
{
struct basic_test_data *data = ptr;
struct event_base *base = data->base;
evwatch_prepare_new(base, &prepare_callback_3, NULL);
event_base_dispatch(base);
}
#ifndef EVENT__DISABLE_MM_REPLACEMENT
static void *
bad_malloc(size_t sz)
{
return NULL;
}
/**
Test that creating prepare and check watchers fails gracefully if we can't
allocate memory.
*/
static void
test_malloc_failure(void *ptr)
{
struct basic_test_data *data = ptr;
struct event_base *base = data->base;
struct evwatch *bad_prepare, *bad_check;
event_set_mem_functions(bad_malloc, realloc, free);
bad_prepare = evwatch_prepare_new(base, &prepare_callback_1, NULL);
tt_ptr_op(bad_prepare, ==, NULL);
bad_check = evwatch_check_new(base, &check_callback_1, NULL);
tt_ptr_op(bad_check, ==, NULL);
event_set_mem_functions(malloc, realloc, free);
end:
;
}
#endif
struct testcase_t watch_testcases[] = {
BASIC(callback_ordering, TT_FORK|TT_NEED_BASE),
BASIC(timeout_unavailable, TT_FORK|TT_NEED_BASE),
#ifndef EVENT__DISABLE_MM_REPLACEMENT
BASIC(malloc_failure, TT_FORK|TT_NEED_BASE),
#endif
END_OF_TESTCASES
};