diff options
Diffstat (limited to 'kit/shared_mutex.h')
| -rw-r--r-- | kit/shared_mutex.h | 176 |
1 files changed, 176 insertions, 0 deletions
diff --git a/kit/shared_mutex.h b/kit/shared_mutex.h new file mode 100644 index 0000000..ad83418 --- /dev/null +++ b/kit/shared_mutex.h @@ -0,0 +1,176 @@ +// Shared mutex can be used in shared memory for interprocess +// synchronization. +// + +#ifndef KIT_SHARED_MUTEX_H +#define KIT_SHARED_MUTEX_H + +#include "atomic.h" +#include "threads.h" + +#include <assert.h> +#include <string.h> + +#ifdef __cplusplus +extern "C" { +#endif + +#if defined(__GNUC__) || defined(__clang__) +# pragma GCC diagnostic push +# pragma GCC diagnostic ignored "-Wunused-function" +# pragma GCC diagnostic ignored "-Wunknown-pragmas" +# pragma GCC push_options +# pragma GCC optimize("O3") +#endif + +enum { + KIT_SHARED_MUTEX_READY = 1, + KIT_SHARED_MUTEX_LOCKED, + KIT_SHARED_MUTEX_WRITER +}; + +typedef union { + struct { + i8 _Atomic state; + i32 readers; + }; + struct { + u8 _pad[16]; + }; +} kit_shared_mutex_t; + +static void kit_shared_mutex_init(kit_shared_mutex_t *m) { + assert(m != NULL); + memset(m, 0, sizeof *m); + + atomic_store_explicit(&m->state, KIT_SHARED_MUTEX_READY, + memory_order_relaxed); +} + +static b8 kit_shared_try_lock(kit_shared_mutex_t *m) { + assert(m != NULL); + + for (;;) { + i8 prev_state = KIT_SHARED_MUTEX_READY; + if (atomic_compare_exchange_strong_explicit( + &m->state, &prev_state, KIT_SHARED_MUTEX_LOCKED, + memory_order_seq_cst, memory_order_seq_cst)) + break; + if (prev_state == KIT_SHARED_MUTEX_WRITER) + return 0; + // FIXME + // Check performance + thrd_yield(); + } + + assert(m->readers >= 0); + ++m->readers; + + i8 prev_state = KIT_SHARED_MUTEX_LOCKED; + if (!atomic_compare_exchange_strong_explicit( + &m->state, &prev_state, KIT_SHARED_MUTEX_READY, + memory_order_seq_cst, memory_order_seq_cst)) + assert(0); + + return 1; +} + +static void kit_shared_lock(kit_shared_mutex_t *m) { + assert(m != NULL); + + while (!kit_shared_try_lock(m)) + // FIXME + // Check performance + thrd_yield(); +} + +static void kit_shared_unlock(kit_shared_mutex_t *m) { + assert(m != NULL); + + for (;;) { + i8 prev_state = KIT_SHARED_MUTEX_READY; + if (atomic_compare_exchange_strong_explicit( + &m->state, &prev_state, KIT_SHARED_MUTEX_LOCKED, + memory_order_seq_cst, memory_order_seq_cst)) + break; + // FIXME + // Check performance + thrd_yield(); + } + + assert(m->readers > 0); + m->readers--; + + i8 prev_state = KIT_SHARED_MUTEX_LOCKED; + if (!atomic_compare_exchange_strong_explicit( + &m->state, &prev_state, KIT_SHARED_MUTEX_READY, + memory_order_seq_cst, memory_order_seq_cst)) + assert(0); +} + +static b8 kit_unique_try_lock(kit_shared_mutex_t *m) { + assert(m != NULL); + + i8 prev_state = KIT_SHARED_MUTEX_READY; + if (!atomic_compare_exchange_strong_explicit( + &m->state, &prev_state, KIT_SHARED_MUTEX_WRITER, + memory_order_seq_cst, memory_order_seq_cst)) + return 0; + + i8 is_locked = (m->readers == 0); + + prev_state = KIT_SHARED_MUTEX_WRITER; + if (!is_locked && + !atomic_compare_exchange_strong_explicit( + &m->state, &prev_state, KIT_SHARED_MUTEX_READY, + memory_order_seq_cst, memory_order_seq_cst)) + assert(0); + + return is_locked; +} + +static void kit_unique_lock(kit_shared_mutex_t *m) { + assert(m != NULL); + + while (!kit_unique_try_lock(m)) + // FIXME + // Check performance + thrd_yield(); +} + +static void kit_unique_unlock(kit_shared_mutex_t *m) { + assert(m != NULL); + + i8 prev_state = KIT_SHARED_MUTEX_WRITER; + if (!atomic_compare_exchange_strong_explicit( + &m->state, &prev_state, KIT_SHARED_MUTEX_READY, + memory_order_seq_cst, memory_order_seq_cst)) + assert(0); +} + +#if defined(__GNUC__) || defined(__clang__) +# pragma GCC pop_options +# pragma GCC diagnostic pop +#endif + +#ifdef __cplusplus +} +#endif + +#define shared_mutex_t kit_shared_mutex_t +#define shared_mutex_init kit_shared_mutex_init +#define shared_try_lock kit_shared_try_lock +#define shared_lock kit_shared_lock +#define shared_unlock kit_shared_unlock +#define unique_try_lock kit_unique_try_lock +#define unique_lock kit_unique_lock +#define unique_unlock kit_unique_unlock +#define shared_mutex_init kit_shared_mutex_init +#define shared_try_lock kit_shared_try_lock +#define shared_lock kit_shared_lock +#define shared_unlock kit_shared_unlock +#define unique_try_lock kit_unique_try_lock +#define unique_lock kit_unique_lock +#define unique_unlock kit_unique_unlock + +#endif |