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isc_async_run() runs events in reverse order

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when more than one event was scheduled in the isc_aysnc queue,
they were executed in reverse order. we need to pull events
off the back of queue instead the front, so that uv_loop will
run them in the right order.

note that isc_job_run() has the same behavior, because it calls
uv_idle_start() directly. in that case we just document it so
it'll be less surprising in the future.
This commit is contained in:
Evan Hunt 2022-10-29 18:05:39 -07:00
parent 0f4af13906
commit dc878e3098
5 changed files with 82 additions and 6 deletions
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4
lib/isc/async.c
View file

@ -47,7 +47,9 @@ isc_async_run(isc_loop_t *loop, isc_job_cb cb, void *cbarg) {
job = isc__job_new(loop, cb, cbarg);
/* Now send the half initialized job to loop queue */
/*
* Now send the half-initialized job to the loop queue.
*/
LOCK(&loop->queue_lock);
ISC_LIST_APPEND(loop->queue_jobs, job, link);
UNLOCK(&loop->queue_lock);

5
lib/isc/include/isc/job.h
View file

@ -39,6 +39,11 @@ isc_job_run(isc_loopmgr_t *loopmgr, isc_job_cb cb, void *cbarg);
* Schedule the job callback 'cb' to be run on the currently
* running event loop.
*
* Note: Because of the design of uv_idle_start(), if more than one
* job is posted at once, the jobs will be pushed onto a stack and
* executed in last-in-first-out order. To post events that are
* executed in order posted, use isc_async_run() instead.
*
* Requires:
*
*\li 'loopmgr' is the active loop manager.

9
lib/isc/loop.c
View file

@ -191,9 +191,14 @@ queue_cb(uv_async_t *handle) {
ISC_LIST_MOVE(list, loop->queue_jobs);
UNLOCK(&loop->queue_lock);
job = ISC_LIST_HEAD(list);
/*
* The ISC_LIST_TAIL is counterintuitive here, but uv_idle
* drains its queue backwards, so if there's more than one event to
* be processed then they need to be in reverse order.
*/
job = ISC_LIST_TAIL(list);
while (job != NULL) {
isc_job_t *next = ISC_LIST_NEXT(job, link);
isc_job_t *next = ISC_LIST_PREV(job, link);
ISC_LIST_UNLINK(list, job, link);
isc__job_init(loop, job);

39
tests/isc/async_test.c
View file

@ -39,9 +39,10 @@ static atomic_uint scheduled = 0;
static void
async_cb(void *arg) {
UNUSED(arg);
uint32_t tid = isc_tid();
UNUSED(arg);
atomic_fetch_add(&scheduled, 1);
if (tid > 0) {
@ -54,11 +55,11 @@ async_cb(void *arg) {
static void
async_setup_cb(void *arg) {
UNUSED(arg);
uint32_t tid = isc_loopmgr_nloops(loopmgr) - 1;
isc_loop_t *loop = isc_loop_get(loopmgr, tid);
UNUSED(arg);
isc_async_run(loop, async_cb, loopmgr);
}
@ -68,8 +69,40 @@ ISC_RUN_TEST_IMPL(isc_async_run) {
assert_int_equal(atomic_load(&scheduled), loopmgr->nloops);
}
static char string[32] = "";
int n1 = 1, n2 = 2, n3 = 3, n4 = 4, n5 = 5;
static void
append(void *arg) {
char value[32];
sprintf(value, "%d", *(int *)arg);
strlcat(string, value, 10);
}
static void
async_multiple(void *arg) {
isc_loop_t *loop = isc_loop_current(loopmgr);
UNUSED(arg);
isc_async_run(loop, append, &n1);
isc_async_run(loop, append, &n2);
isc_async_run(loop, append, &n3);
isc_async_run(loop, append, &n4);
isc_async_run(loop, append, &n5);
isc_loopmgr_shutdown(loopmgr);
}
ISC_RUN_TEST_IMPL(isc_async_multiple) {
string[0] = '\0';
isc_loop_setup(isc_loop_main(loopmgr), async_multiple, loopmgr);
isc_loopmgr_run(loopmgr);
assert_string_equal(string, "12345");
}
ISC_TEST_LIST_START
ISC_TEST_ENTRY_CUSTOM(isc_async_run, setup_loopmgr, teardown_loopmgr)
ISC_TEST_ENTRY_CUSTOM(isc_async_multiple, setup_loopmgr, teardown_loopmgr)
ISC_TEST_LIST_END
ISC_TEST_MAIN

31
tests/isc/job_test.c
View file

@ -76,8 +76,39 @@ ISC_RUN_TEST_IMPL(isc_job_run) {
assert_int_equal(atomic_load(&scheduled), atomic_load(&executed));
}
static char string[32] = "";
int n1 = 1, n2 = 2, n3 = 3, n4 = 4, n5 = 5;
static void
append(void *arg) {
char value[32];
sprintf(value, "%d", *(int *)arg);
strlcat(string, value, 10);
}
static void
job_multiple(void *arg) {
UNUSED(arg);
/* These will be processed in reverse order */
isc_job_run(loopmgr, append, &n1);
isc_job_run(loopmgr, append, &n2);
isc_job_run(loopmgr, append, &n3);
isc_job_run(loopmgr, append, &n4);
isc_job_run(loopmgr, append, &n5);
isc_loopmgr_shutdown(loopmgr);
}
ISC_RUN_TEST_IMPL(isc_job_multiple) {
string[0] = '\0';
isc_loop_setup(isc_loop_main(loopmgr), job_multiple, loopmgr);
isc_loopmgr_run(loopmgr);
assert_string_equal(string, "54321");
}
ISC_TEST_LIST_START
ISC_TEST_ENTRY_CUSTOM(isc_job_run, setup_loopmgr, teardown_loopmgr)
ISC_TEST_ENTRY_CUSTOM(isc_job_multiple, setup_loopmgr, teardown_loopmgr)
ISC_TEST_LIST_END
ISC_TEST_MAIN