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use atomic yield on delayed-freeing; clarify code

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This commit is contained in:
daan 2020-01-23 09:57:55 -08:00
parent 3bbbe6c686
commit 66818bf632
4 changed files with 39 additions and 38 deletions
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7
src/page.c
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@ -126,12 +126,12 @@ void _mi_page_use_delayed_free(mi_page_t* page, mi_delayed_t delay, bool overrid
mi_thread_free_t tfreex;
mi_delayed_t old_delay;
do {
tfree = mi_atomic_read(&page->xthread_free);
tfree = mi_atomic_read(&page->xthread_free); // note: must acquire as we can break this loop and not do a CAS
tfreex = mi_tf_set_delayed(tfree, delay);
old_delay = mi_tf_delayed(tfree);
if (mi_unlikely(old_delay == MI_DELAYED_FREEING)) {
mi_atomic_yield(); // delay until outstanding MI_DELAYED_FREEING are done.
tfree = mi_tf_set_delayed(tfree, MI_NO_DELAYED_FREE); // will cause CAS to busy fail
// tfree = mi_tf_set_delayed(tfree, MI_NO_DELAYED_FREE); // will cause CAS to busy fail
}
else if (delay == old_delay) {
break; // avoid atomic operation if already equal
@ -139,7 +139,8 @@ void _mi_page_use_delayed_free(mi_page_t* page, mi_delayed_t delay, bool overrid
else if (!override_never && old_delay == MI_NEVER_DELAYED_FREE) {
break; // leave never-delayed flag set
}
} while (!mi_atomic_cas_weak(&page->xthread_free, tfreex, tfree));
} while ((old_delay == MI_DELAYED_FREEING) ||
!mi_atomic_cas_weak(&page->xthread_free, tfreex, tfree));
}
/* -----------------------------------------------------------