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Make _cyclic_ timers interval more deterministic - next timeout is calculated from last due time instead of relative to current time

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This eliminates the cyclic timer jitter
This commit is contained in:
Dirk Ziegelmeier 2018-01-05 13:45:51 +01:00
parent 2b4dde84e3
commit eaca067c7d
3 changed files with 100 additions and 62 deletions
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38
src/core/timeouts.c
View File

@ -67,7 +67,7 @@
#endif /* LWIP_DEBUG_TIMERNAMES */
/* Check if timer's expiry time is greater than time and care about u32_t wraparounds */
#define TIMER_LESS_THAN(timer, t) ( (((timer)->time == (t)) || (((u32_t)((timer)->time-(t))) > 0x7fffffff)) ? 1 : 0 )
#define TIME_LESS_THAN(t, compare_to) ( (((t) == (compare_to)) || (((u32_t)((t)-(compare_to))) > 0x7fffffff)) ? 1 : 0 )
/** This array contains all stack-internal cyclic timers. To get the number of
* timers, use LWIP_ARRAYSIZE() */
@ -115,6 +115,8 @@ const int lwip_num_cyclic_timers = LWIP_ARRAYSIZE(lwip_cyclic_timers);
/** The one and only timeout list */
static struct sys_timeo *next_timeout;
static u32_t current_timeout_due_time;
#if LWIP_TESTMODE
struct sys_timeo**
lwip_sys_timers_get_next_timout(void)
@ -173,15 +175,30 @@ tcp_timer_needed(void)
*
* @param arg unused argument
*/
static void
cyclic_timer(void *arg)
#if !LWIP_TESTMODE
static
#endif
void
lwip_cyclic_timer(void *arg)
{
u32_t now;
u32_t next_timeout;
const struct lwip_cyclic_timer *cyclic = (const struct lwip_cyclic_timer *)arg;
#if LWIP_DEBUG_TIMERNAMES
LWIP_DEBUGF(TIMERS_DEBUG, ("tcpip: %s()\n", cyclic->handler_name));
#endif
cyclic->handler();
sys_timeout(cyclic->interval_ms, cyclic_timer, arg);
now = sys_now();
next_timeout = (u32_t)(current_timeout_due_time + cyclic->interval_ms);
if (TIME_LESS_THAN(next_timeout, now)) {
/* timer would immediately expire again -> "overload" -> restart without any correction */
sys_timeout(cyclic->interval_ms, lwip_cyclic_timer, arg);
} else {
/* correct cyclic interval with handler execution delay and sys_check_timeouts jitter */
sys_timeout((u32_t)(next_timeout - now), lwip_cyclic_timer, arg);
}
}
/** Initialize this module */
@ -192,7 +209,7 @@ void sys_timeouts_init(void)
for (i = (LWIP_TCP ? 1 : 0); i < LWIP_ARRAYSIZE(lwip_cyclic_timers); i++) {
/* we have to cast via size_t to get rid of const warning
(this is OK as cyclic_timer() casts back to const* */
sys_timeout(lwip_cyclic_timers[i].interval_ms, cyclic_timer, LWIP_CONST_CAST(void *, &lwip_cyclic_timers[i]));
sys_timeout(lwip_cyclic_timers[i].interval_ms, lwip_cyclic_timer, LWIP_CONST_CAST(void *, &lwip_cyclic_timers[i]));
}
}
@ -230,7 +247,7 @@ sys_timeout(u32_t msecs, sys_timeout_handler handler, void *arg)
timeout->next = NULL;
timeout->h = handler;
timeout->arg = arg;
timeout->time = (u32_t)(now + msecs); /* overflow handled by TIMER_LESS_THAN macro */
timeout->time = (u32_t)(now + msecs); /* overflow handled by TIME_LESS_THAN macro */
#if LWIP_DEBUG_TIMERNAMES
timeout->handler_name = handler_name;
LWIP_DEBUGF(TIMERS_DEBUG, ("sys_timeout: %p msecs=%"U32_F" handler=%s arg=%p\n",
@ -241,12 +258,12 @@ sys_timeout(u32_t msecs, sys_timeout_handler handler, void *arg)
next_timeout = timeout;
return;
}
if (TIMER_LESS_THAN(timeout, next_timeout->time)) {
if (TIME_LESS_THAN(timeout->time, next_timeout->time)) {
timeout->next = next_timeout;
next_timeout = timeout;
} else {
for (t = next_timeout; t != NULL; t = t->next) {
if ((t->next == NULL) || TIMER_LESS_THAN(timeout, t->next->time)) {
if ((t->next == NULL) || TIME_LESS_THAN(timeout->time, t->next->time)) {
timeout->next = t->next;
t->next = timeout;
break;
@ -322,12 +339,13 @@ sys_check_timeouts(void)
had_one = 0;
tmptimeout = next_timeout;
now = sys_now();
if (tmptimeout && TIMER_LESS_THAN(tmptimeout, now)) {
if (tmptimeout && TIME_LESS_THAN(tmptimeout->time, now)) {
/* timeout has expired */
had_one = 1;
next_timeout = tmptimeout->next;
handler = tmptimeout->h;
arg = tmptimeout->arg;
current_timeout_due_time = tmptimeout->time;
#if LWIP_DEBUG_TIMERNAMES
if (handler != NULL) {
LWIP_DEBUGF(TIMERS_DEBUG, ("sct calling h=%s arg=%p\n",
@ -373,7 +391,7 @@ sys_timeouts_sleeptime(void)
return 0xffffffff;
}
now = sys_now();
if (TIMER_LESS_THAN(next_timeout, now)) {
if (TIME_LESS_THAN(next_timeout->time, now)) {
return 0;
} else {
return (u32_t)(next_timeout->time - now);

1
src/include/lwip/timeouts.h
View File

@ -116,6 +116,7 @@ void sys_timeouts_mbox_fetch(sys_mbox_t *mbox, void **msg);
#if LWIP_TESTMODE
struct sys_timeo** lwip_sys_timers_get_next_timout(void);
void lwip_cyclic_timer(void *arg);
#endif
#endif /* LWIP_TIMERS */

123
test/unit/core/test_timers.c
View File

@ -31,7 +31,65 @@ static void dummy_handler(void* arg)
fired[index] = 1;
}
/* reproduce bug bug #52748: the bug in timeouts.c */
#define HANDLER_EXECUTION_TIME 5
static int cyclic_fired;
static void dummy_cyclic_handler(void)
{
cyclic_fired = 1;
lwip_sys_now += HANDLER_EXECUTION_TIME;
}
struct lwip_cyclic_timer test_cyclic = {10, dummy_cyclic_handler};
void do_test_cyclic_timers(u32_t offset)
{
struct sys_timeo** list_head = lwip_sys_timers_get_next_timout();
/* verify normal timer expiration */
lwip_sys_now = offset + 0;
sys_timeout(test_cyclic.interval_ms, lwip_cyclic_timer, &test_cyclic);
cyclic_fired = 0;
sys_check_timeouts();
fail_unless(cyclic_fired == 0);
lwip_sys_now = offset + test_cyclic.interval_ms;
sys_check_timeouts();
fail_unless(cyclic_fired == 1);
fail_unless((*list_head)->time == (u32_t)(lwip_sys_now + test_cyclic.interval_ms - HANDLER_EXECUTION_TIME));
sys_untimeout(lwip_cyclic_timer, &test_cyclic);
/* verify "overload" - next cyclic timer execution is already overdue twice */
lwip_sys_now = offset + 0;
sys_timeout(test_cyclic.interval_ms, lwip_cyclic_timer, &test_cyclic);
cyclic_fired = 0;
sys_check_timeouts();
fail_unless(cyclic_fired == 0);
lwip_sys_now = offset + 2*test_cyclic.interval_ms;
sys_check_timeouts();
fail_unless(cyclic_fired == 1);
fail_unless((*list_head)->time == (u32_t)(lwip_sys_now + test_cyclic.interval_ms));
}
START_TEST(test_cyclic_timers)
{
LWIP_UNUSED_ARG(_i);
/* check without u32_t wraparound */
do_test_cyclic_timers(0);
/* check with u32_t wraparound */
do_test_cyclic_timers(0xfffffff0);
}
END_TEST
/* reproduce bug #52748: the bug in timeouts.c */
START_TEST(test_bug52748)
{
LWIP_UNUSED_ARG(_i);
@ -63,15 +121,11 @@ START_TEST(test_bug52748)
}
END_TEST
START_TEST(test_timers)
void do_test_timers(u32_t offset)
{
struct sys_timeo** list_head = lwip_sys_timers_get_next_timout();
LWIP_UNUSED_ARG(_i);
/* check without u32_t wraparound */
lwip_sys_now = 100;
lwip_sys_now = offset + 0;
sys_timeout(10, dummy_handler, LWIP_PTR_NUMERIC_CAST(void*, 0));
fail_unless(sys_timeouts_sleeptime() == 10);
@ -115,53 +169,17 @@ START_TEST(test_timers)
sys_untimeout(dummy_handler, LWIP_PTR_NUMERIC_CAST(void*, 0));
sys_untimeout(dummy_handler, LWIP_PTR_NUMERIC_CAST(void*, 1));
sys_untimeout(dummy_handler, LWIP_PTR_NUMERIC_CAST(void*, 2));
}
/* check u32_t wraparound */
START_TEST(test_timers)
{
LWIP_UNUSED_ARG(_i);
lwip_sys_now = 0xfffffff5;
/* check without u32_t wraparound */
do_test_timers(0);
sys_timeout(10, dummy_handler, LWIP_PTR_NUMERIC_CAST(void*, 0));
fail_unless(sys_timeouts_sleeptime() == 10);
sys_timeout(20, dummy_handler, LWIP_PTR_NUMERIC_CAST(void*, 1));
fail_unless(sys_timeouts_sleeptime() == 10);
sys_timeout( 5, dummy_handler, LWIP_PTR_NUMERIC_CAST(void*, 2));
fail_unless(sys_timeouts_sleeptime() == 5);
/* linked list correctly sorted? */
fail_unless((*list_head)->time == (u32_t)(lwip_sys_now + 5));
fail_unless((*list_head)->next->time == (u32_t)(lwip_sys_now + 10));
fail_unless((*list_head)->next->next->time == (u32_t)(lwip_sys_now + 20));
/* check timers expire in correct order */
memset(&fired, 0, sizeof(fired));
lwip_sys_now += 4;
sys_check_timeouts();
fail_unless(fired[2] == 0);
lwip_sys_now += 1;
sys_check_timeouts();
fail_unless(fired[2] == 1);
lwip_sys_now += 4;
sys_check_timeouts();
fail_unless(fired[0] == 0);
lwip_sys_now += 1;
sys_check_timeouts();
fail_unless(fired[0] == 1);
lwip_sys_now += 9;
sys_check_timeouts();
fail_unless(fired[1] == 0);
lwip_sys_now += 1;
sys_check_timeouts();
fail_unless(fired[1] == 1);
sys_untimeout(dummy_handler, LWIP_PTR_NUMERIC_CAST(void*, 0));
sys_untimeout(dummy_handler, LWIP_PTR_NUMERIC_CAST(void*, 1));
sys_untimeout(dummy_handler, LWIP_PTR_NUMERIC_CAST(void*, 2));
/* check with u32_t wraparound */
do_test_timers(0xfffffff0);
}
END_TEST
@ -171,6 +189,7 @@ timers_suite(void)
{
testfunc tests[] = {
TESTFUNC(test_bug52748),
TESTFUNC(test_cyclic_timers),
TESTFUNC(test_timers)
};
testfunc tests_unused[] = {