| 1 | #include "object-state.h" |
| 2 | |
| 3 | OBJECT_STATE_ID object_state_id(OBJECT_STATE *os) { |
| 4 | return __atomic_load_n(&os->state_id, __ATOMIC_ACQUIRE); |
| 5 | } |
| 6 | |
| 7 | void object_state_activate(OBJECT_STATE *os) { |
| 8 | __atomic_add_fetch(&os->state_id, 1, __ATOMIC_RELAXED); |
| 9 | |
| 10 | REFCOUNT expected = __atomic_load_n(&os->state_refcount, __ATOMIC_RELAXED); |
| 11 | REFCOUNT desired; |
| 12 | |
| 13 | do { |
| 14 | if(expected != OBJECT_STATE_DEACTIVATED) { |
| 15 | fatal("OBJECT_STATE: attempt to activate already activated object (state refcount is %d)", expected); |
| 16 | return; |
| 17 | } |
| 18 | |
| 19 | desired = 0; |
| 20 | |
| 21 | } while(!__atomic_compare_exchange_n( |
| 22 | &os->state_refcount, &expected, desired, false, __ATOMIC_ACQUIRE, __ATOMIC_RELAXED)); |
| 23 | } |
| 24 | |
| 25 | void object_state_activate_if_not_activated(OBJECT_STATE *os) { |
| 26 | __atomic_add_fetch(&os->state_id, 1, __ATOMIC_RELAXED); |
| 27 | |
| 28 | REFCOUNT expected = __atomic_load_n(&os->state_refcount, __ATOMIC_RELAXED); |
| 29 | REFCOUNT desired; |
| 30 | |
| 31 | do { |
| 32 | if(expected != OBJECT_STATE_DEACTIVATED) |
| 33 | return; |
| 34 | |
| 35 | desired = 0; |
| 36 | |
| 37 | } while(!__atomic_compare_exchange_n( |
| 38 | &os->state_refcount, &expected, desired, false, __ATOMIC_ACQUIRE, __ATOMIC_RELAXED)); |
| 39 | } |
| 40 | |
| 41 | void object_state_deactivate(OBJECT_STATE *os) { |
| 42 | __atomic_add_fetch(&os->state_id, 1, __ATOMIC_RELAXED); |
| 43 | |
| 44 | REFCOUNT expected = __atomic_load_n(&os->state_refcount, __ATOMIC_RELAXED); |
| 45 | REFCOUNT desired; |
| 46 | |
| 47 | do { |
| 48 | if(expected == OBJECT_STATE_DEACTIVATED) { |
| 49 | fatal("OBJECT_STATE: attempt to deactivate object that is already deactivated (state refcount %d)", expected); |
| 50 | return; |
| 51 | } |
| 52 | else if(expected < 0) { |
| 53 | fatal("OBJECT_STATE: attempt to deactivate object that is already deactivating (state refcount %d)", expected); |
| 54 | return; |
| 55 | } |
| 56 | |
| 57 | // Current (-INT32_MAX) + holders |
| 58 | desired = OBJECT_STATE_DEACTIVATED + expected; |
| 59 | |
| 60 | } while(!__atomic_compare_exchange_n( |
| 61 | &os->state_refcount, &expected, desired, false, __ATOMIC_SEQ_CST, __ATOMIC_RELAXED)); |
| 62 | |
| 63 | // Now wait for all holders to release |
| 64 | while(__atomic_load_n(&os->state_refcount, __ATOMIC_ACQUIRE) != OBJECT_STATE_DEACTIVATED) |
| 65 | tinysleep(); // Busy wait until all holders are gone |
| 66 | } |
| 67 | |
| 68 | bool object_state_acquire(OBJECT_STATE *os, OBJECT_STATE_ID wanted_state_id) { |
| 69 | REFCOUNT expected = __atomic_load_n(&os->state_refcount, __ATOMIC_RELAXED); |
| 70 | REFCOUNT desired; |
| 71 | |
| 72 | do { |
| 73 | // If refcount is negative, it means deactivation is in progress or complete |
| 74 | if(expected < 0) |
| 75 | return false; |
| 76 | |
| 77 | desired = expected + 1; |
| 78 | |
| 79 | } while(!__atomic_compare_exchange_n( |
| 80 | &os->state_refcount, &expected, desired, false, __ATOMIC_ACQUIRE, __ATOMIC_RELAXED)); |
| 81 | |
| 82 | if(object_state_id(os) != wanted_state_id) { |
| 83 | object_state_release(os); |
| 84 | return false; |
| 85 | } |
| 86 | |
| 87 | return true; |
| 88 | } |
| 89 | |
| 90 | void object_state_release(OBJECT_STATE *os) { |
| 91 | __atomic_sub_fetch(&os->state_refcount, 1, __ATOMIC_RELEASE); |
| 92 | } |