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Enforce deadline reached on timeout

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The value of sc_tick_now() has microsecond precision, but
sc_cond_timedwait() has only millisecond precision.

To guarantee that sc_tick_now() >= deadline when sc_cond_timedwait()
returns due to timeout, round up to the next millisecond.

This avoids to call a non-blocking sc_cond_timedwait() in a loop for no
reason until a target deadline during up to 1 millisecond.

Refs 682a691173
This commit is contained in:
Romain Vimont 2022-02-16 18:29:30 +01:00
parent 2a872c3865
commit 85edba20e7
1 changed files with 5 additions and 1 deletions
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6
app/src/util/thread.c
View file

@ -136,7 +136,9 @@ sc_cond_timedwait(sc_cond *cond, sc_mutex *mutex, sc_tick deadline) {
return false; // timeout return false; // timeout
} }
uint32_t ms = SC_TICK_TO_MS(deadline - now); // Round up to the next millisecond to guarantee that the deadline is
// reached when returning due to timeout
uint32_t ms = SC_TICK_TO_MS(deadline - now + SC_TICK_FROM_MS(1) - 1);
int r = SDL_CondWaitTimeout(cond->cond, mutex->mutex, ms); int r = SDL_CondWaitTimeout(cond->cond, mutex->mutex, ms);
#ifndef NDEBUG #ifndef NDEBUG
if (r < 0) { if (r < 0) {
@ -148,6 +150,8 @@ sc_cond_timedwait(sc_cond *cond, sc_mutex *mutex, sc_tick deadline) {
memory_order_relaxed); memory_order_relaxed);
#endif #endif
assert(r == 0 || r == SDL_MUTEX_TIMEDOUT); assert(r == 0 || r == SDL_MUTEX_TIMEDOUT);
// The deadline is reached on timeout
assert(r != SDL_MUTEX_TIMEDOUT || sc_tick_now() >= deadline);
return r == 0; return r == 0;
} }