mirror of
https://github.com/Mathewnd/Astral.git
synced 2026-10-27 12:48:22 +00:00
pushlock: rewrite implementation
This commit is contained in:
Matheus
@@ -12,7 +12,7 @@ typedef pushlock_t mutex_t;
|
||||
pushlock_acquire_exclusive(m)
|
||||
|
||||
#define MUTEX_RELEASE(m) \
|
||||
pushlock_release(m)
|
||||
pushlock_release_exclusive(m)
|
||||
|
||||
#define MUTEX_TRY(m) \
|
||||
pushlock_try_acquire_exclusive(m)
|
||||
|
||||
@@ -1,31 +1,18 @@
|
||||
#ifndef _RWLOCK_H
|
||||
#define _RWLOCK_H
|
||||
#ifndef _PUSHLOCK_H
|
||||
#define _PUSHLOCK_H
|
||||
|
||||
#include <semaphore.h>
|
||||
|
||||
typedef struct pushlock_wait_block_t {
|
||||
struct pushlock_wait_block_t *next;
|
||||
size_t shared_count;
|
||||
semaphore_t semaphore;
|
||||
} __attribute__((aligned(8))) pushlock_wait_block_t;
|
||||
#include <stdint.h>
|
||||
#include <stdbool.h>
|
||||
|
||||
typedef uintptr_t pushlock_t;
|
||||
|
||||
#define PUSHLOCK_FLAGS_ACQUIRED 1
|
||||
#define PUSHLOCK_FLAGS_EXCLUSIVE 2
|
||||
#define PUSHLOCK_FLAGS_CONTENDED 4
|
||||
#define PUSHLOCK_MASK_FLAGS 0x7
|
||||
#define PUSHLOCK_MASK_POINTER_SHARED_COUNT (0xfffffffffffffff8lu)
|
||||
|
||||
#define PUSHLOCK_GET_POINTER(x) ((pushlock_wait_block_t *)((x) & PUSHLOCK_MASK_POINTER_SHARED_COUNT))
|
||||
#define PUSHLOCK_GET_SHARED_COUNT(x) ((uintptr_t)PUSHLOCK_GET_POINTER(x) >> 3)
|
||||
#define PUSHLOCK_INCREMENT_SHARED_COUNT(x) ((x) + 0x8)
|
||||
#define PUSHLOCK_DECREMENT_SHARED_COUNT(x) ((x) - 0x8)
|
||||
|
||||
bool pushlock_try_acquire_exclusive(pushlock_t *pushlock);
|
||||
void pushlock_acquire_exclusive(pushlock_t *pushlock);
|
||||
bool pushlock_try_acquire_shared(pushlock_t *pushlock);
|
||||
|
||||
void pushlock_acquire_exclusive(pushlock_t *pushlock);
|
||||
void pushlock_acquire_shared(pushlock_t *pushlock);
|
||||
void pushlock_release(pushlock_t *pushlock);
|
||||
|
||||
void pushlock_release_exclusive(pushlock_t *pushlock);
|
||||
void pushlock_release_shared(pushlock_t *pushlock);
|
||||
|
||||
#endif
|
||||
|
||||
+165
-112
@@ -1,165 +1,218 @@
|
||||
#include <pushlock.h>
|
||||
#include <semaphore.h>
|
||||
#include <logging.h>
|
||||
#define DO_CAS(ptr, saved, new) \
|
||||
__atomic_compare_exchange_n(ptr, &saved, new, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)
|
||||
|
||||
#define CAS_ACQUIRE__RELAXED(ptr, saved, new) \
|
||||
__atomic_compare_exchange_n(ptr, &saved, new, false, __ATOMIC_ACQUIRE, __ATOMIC_RELAXED)
|
||||
|
||||
#define CAS_RELEASE__RELAXED(ptr, saved, new) \
|
||||
__atomic_compare_exchange_n(ptr, &saved, new, false, __ATOMIC_RELEASE, __ATOMIC_RELAXED)
|
||||
|
||||
typedef struct pushlock_wait_block_t {
|
||||
struct pushlock_wait_block_t *next;
|
||||
size_t shared_count;
|
||||
semaphore_t semaphore;
|
||||
} __attribute__((aligned(8))) pushlock_wait_block_t;
|
||||
|
||||
#define PUSHLOCK_FLAGS_ACQUIRED 1
|
||||
#define PUSHLOCK_FLAGS_EXCLUSIVE 2
|
||||
#define PUSHLOCK_FLAGS_CONTENDED 4
|
||||
#define PUSHLOCK_MASK_FLAGS 0x7
|
||||
#define PUSHLOCK_MASK_POINTER_SHARED_COUNT (0xfffffffffffffff8lu)
|
||||
|
||||
#define PUSHLOCK_GET_POINTER(x) ((pushlock_wait_block_t *)((x) & PUSHLOCK_MASK_POINTER_SHARED_COUNT))
|
||||
#define PUSHLOCK_GET_SHARED_COUNT(x) ((uintptr_t)PUSHLOCK_GET_POINTER(x) >> 3)
|
||||
#define PUSHLOCK_INCREMENT_SHARED_COUNT(x) ((x) + 0x8)
|
||||
#define PUSHLOCK_DECREMENT_SHARED_COUNT(x) ((x) - 0x8)
|
||||
|
||||
bool pushlock_try_acquire_exclusive(pushlock_t *pushlock) {
|
||||
for (;;) {
|
||||
pushlock_t saved_value = *pushlock;
|
||||
if ((PUSHLOCK_FLAGS_ACQUIRED & saved_value) == 0) {
|
||||
if (DO_CAS(pushlock, saved_value, saved_value | PUSHLOCK_FLAGS_ACQUIRED | PUSHLOCK_FLAGS_EXCLUSIVE))
|
||||
retry_lock:
|
||||
pushlock_t saved_value = 0;
|
||||
if (CAS_ACQUIRE__RELAXED(pushlock, saved_value, PUSHLOCK_FLAGS_ACQUIRED | PUSHLOCK_FLAGS_EXCLUSIVE))
|
||||
return true;
|
||||
|
||||
continue;
|
||||
}
|
||||
|
||||
if (saved_value & PUSHLOCK_FLAGS_ACQUIRED)
|
||||
return false;
|
||||
}
|
||||
|
||||
if (!CAS_ACQUIRE__RELAXED(pushlock, saved_value, saved_value | PUSHLOCK_FLAGS_ACQUIRED | PUSHLOCK_FLAGS_EXCLUSIVE))
|
||||
goto retry_lock;
|
||||
|
||||
return true;
|
||||
}
|
||||
|
||||
void pushlock_acquire_exclusive(pushlock_t *pushlock) {
|
||||
for (;;) {
|
||||
pushlock_t saved_value = *pushlock;
|
||||
if ((PUSHLOCK_FLAGS_ACQUIRED & saved_value) == 0) {
|
||||
if (DO_CAS(pushlock, saved_value, saved_value | PUSHLOCK_FLAGS_ACQUIRED | PUSHLOCK_FLAGS_EXCLUSIVE))
|
||||
retry_lock:
|
||||
pushlock_t saved_value = 0;
|
||||
if (CAS_ACQUIRE__RELAXED(pushlock, saved_value, PUSHLOCK_FLAGS_ACQUIRED | PUSHLOCK_FLAGS_EXCLUSIVE))
|
||||
return;
|
||||
|
||||
continue;
|
||||
}
|
||||
if ((saved_value & PUSHLOCK_FLAGS_ACQUIRED) == 0 && CAS_ACQUIRE__RELAXED(pushlock, saved_value, saved_value | PUSHLOCK_FLAGS_ACQUIRED | PUSHLOCK_FLAGS_EXCLUSIVE))
|
||||
return;
|
||||
|
||||
pushlock_wait_block_t wait_block;
|
||||
SEMAPHORE_INIT(&wait_block.semaphore, 0);
|
||||
|
||||
if (saved_value & PUSHLOCK_FLAGS_CONTENDED) {
|
||||
wait_block.next = PUSHLOCK_GET_POINTER(saved_value);
|
||||
wait_block.shared_count = 0;
|
||||
__atomic_store_n(&wait_block.shared_count, 0, __ATOMIC_RELAXED);
|
||||
} else {
|
||||
wait_block.next = NULL;
|
||||
wait_block.shared_count = PUSHLOCK_GET_SHARED_COUNT(saved_value);
|
||||
__atomic_store_n(&wait_block.shared_count, PUSHLOCK_GET_SHARED_COUNT(saved_value), __ATOMIC_RELAXED);
|
||||
}
|
||||
|
||||
if (DO_CAS(pushlock, saved_value, (uintptr_t)&wait_block | (saved_value & PUSHLOCK_MASK_FLAGS) | PUSHLOCK_FLAGS_CONTENDED))
|
||||
if (CAS_RELEASE__RELAXED(pushlock, saved_value, (uintptr_t)&wait_block | (saved_value & PUSHLOCK_MASK_FLAGS) | PUSHLOCK_FLAGS_CONTENDED))
|
||||
semaphore_wait(&wait_block.semaphore, false);
|
||||
}
|
||||
|
||||
goto retry_lock;
|
||||
}
|
||||
|
||||
bool pushlock_try_acquire_shared(pushlock_t *pushlock) {
|
||||
for (;;) {
|
||||
pushlock_t saved_value = *pushlock;
|
||||
if ((saved_value & PUSHLOCK_FLAGS_ACQUIRED) == 0 || (saved_value & PUSHLOCK_FLAGS_EXCLUSIVE) == 0) {
|
||||
if (saved_value & PUSHLOCK_FLAGS_CONTENDED) {
|
||||
// if its contended, we will try to acquire it as an exclusive lock
|
||||
// (as we have no space for putting the shared count in the pointer)
|
||||
if (DO_CAS(pushlock, saved_value, saved_value | PUSHLOCK_FLAGS_ACQUIRED | PUSHLOCK_FLAGS_EXCLUSIVE))
|
||||
retry_lock:
|
||||
pushlock_t saved_value = 0;
|
||||
if (CAS_ACQUIRE__RELAXED(pushlock, saved_value, PUSHLOCK_INCREMENT_SHARED_COUNT(PUSHLOCK_FLAGS_ACQUIRED)))
|
||||
return true;
|
||||
} else {
|
||||
// its not contended and either unlocked or locked shared
|
||||
// set the appropriate flag and increment the shared count
|
||||
if (DO_CAS(pushlock, saved_value, PUSHLOCK_INCREMENT_SHARED_COUNT(saved_value) | PUSHLOCK_FLAGS_ACQUIRED))
|
||||
return true;
|
||||
}
|
||||
|
||||
continue;
|
||||
}
|
||||
|
||||
if (saved_value & PUSHLOCK_FLAGS_EXCLUSIVE)
|
||||
return false;
|
||||
|
||||
if ((saved_value & PUSHLOCK_FLAGS_CONTENDED) == 0) {
|
||||
if (!CAS_ACQUIRE__RELAXED(pushlock, saved_value, PUSHLOCK_INCREMENT_SHARED_COUNT(saved_value)))
|
||||
goto retry_lock;
|
||||
|
||||
return true;
|
||||
}
|
||||
|
||||
if (saved_value & PUSHLOCK_FLAGS_ACQUIRED)
|
||||
return false;
|
||||
|
||||
// try to acquire as exclusive
|
||||
if (!CAS_ACQUIRE__RELAXED(pushlock, saved_value, saved_value | PUSHLOCK_FLAGS_ACQUIRED | PUSHLOCK_FLAGS_EXCLUSIVE))
|
||||
goto retry_lock;
|
||||
|
||||
return true;
|
||||
}
|
||||
|
||||
void pushlock_acquire_shared(pushlock_t *pushlock) {
|
||||
for (;;) {
|
||||
pushlock_t saved_value = *pushlock;
|
||||
if ((saved_value & PUSHLOCK_FLAGS_ACQUIRED) == 0 || (saved_value & PUSHLOCK_FLAGS_EXCLUSIVE) == 0) {
|
||||
if (saved_value & PUSHLOCK_FLAGS_CONTENDED) {
|
||||
// if its contended, we will try to acquire it as an exclusive lock
|
||||
// (as we have no space for putting the shared count in the pointer)
|
||||
if (DO_CAS(pushlock, saved_value, saved_value | PUSHLOCK_FLAGS_ACQUIRED | PUSHLOCK_FLAGS_EXCLUSIVE))
|
||||
retry_lock:
|
||||
pushlock_t saved_value = 0;
|
||||
if (CAS_ACQUIRE__RELAXED(pushlock, saved_value, PUSHLOCK_INCREMENT_SHARED_COUNT(PUSHLOCK_FLAGS_ACQUIRED)))
|
||||
return;
|
||||
} else {
|
||||
// its not contended and either unlocked or locked shared
|
||||
// set the appropriate flag and increment the shared count
|
||||
if (DO_CAS(pushlock, saved_value, PUSHLOCK_INCREMENT_SHARED_COUNT(saved_value) | PUSHLOCK_FLAGS_ACQUIRED))
|
||||
return;
|
||||
}
|
||||
|
||||
continue;
|
||||
}
|
||||
|
||||
if ((saved_value & PUSHLOCK_FLAGS_EXCLUSIVE) || ((saved_value & PUSHLOCK_FLAGS_ACQUIRED) && (saved_value & PUSHLOCK_FLAGS_CONTENDED))) {
|
||||
pushlock_wait_block_t wait_block;
|
||||
SEMAPHORE_INIT(&wait_block.semaphore, 0);
|
||||
|
||||
// lock is being exclusively held, which means the bits for shared_count
|
||||
// is the pointer to the first wait block, so we can directly get it here
|
||||
wait_block.next = PUSHLOCK_GET_POINTER(saved_value);
|
||||
wait_block.shared_count = 0;
|
||||
__atomic_store_n(&wait_block.shared_count, 0, __ATOMIC_RELAXED);
|
||||
|
||||
if (DO_CAS(pushlock, saved_value, (uintptr_t)&wait_block | (saved_value & PUSHLOCK_MASK_FLAGS) | PUSHLOCK_FLAGS_CONTENDED))
|
||||
if (CAS_RELEASE__RELAXED(pushlock, saved_value, (uintptr_t)&wait_block | (saved_value & PUSHLOCK_MASK_FLAGS) | PUSHLOCK_FLAGS_CONTENDED))
|
||||
semaphore_wait(&wait_block.semaphore, false);
|
||||
|
||||
goto retry_lock;
|
||||
}
|
||||
|
||||
if (saved_value & PUSHLOCK_FLAGS_ACQUIRED) {
|
||||
if (!CAS_ACQUIRE__RELAXED(pushlock, saved_value, PUSHLOCK_INCREMENT_SHARED_COUNT(saved_value)))
|
||||
goto retry_lock;
|
||||
|
||||
return;
|
||||
}
|
||||
|
||||
if (!CAS_ACQUIRE__RELAXED(pushlock, saved_value, saved_value | PUSHLOCK_FLAGS_ACQUIRED | PUSHLOCK_FLAGS_EXCLUSIVE))
|
||||
goto retry_lock;
|
||||
}
|
||||
|
||||
void pushlock_release(pushlock_t *pushlock) {
|
||||
pushlock_t saved_value;
|
||||
for (;;) {
|
||||
saved_value = *pushlock;
|
||||
// TODO: if we are releasing to a shared waiter, we should wake up every shared waiter
|
||||
void pushlock_release_exclusive(pushlock_t *pushlock) {
|
||||
pushlock_t saved_value = PUSHLOCK_FLAGS_ACQUIRED | PUSHLOCK_FLAGS_EXCLUSIVE;
|
||||
if (CAS_RELEASE__RELAXED(pushlock, saved_value, 0))
|
||||
return;
|
||||
|
||||
#ifdef DEBUG_LOCKS
|
||||
__assert(saved_value & PUSHLOCK_FLAGS_ACQUIRED);
|
||||
__assert(saved_value & PUSHLOCK_FLAGS_EXCLUSIVE);
|
||||
#endif
|
||||
|
||||
__atomic_thread_fence(__ATOMIC_ACQUIRE);
|
||||
pushlock_wait_block_t *wait_block = PUSHLOCK_GET_POINTER(saved_value);
|
||||
if (wait_block->next == NULL) {
|
||||
if (CAS_RELEASE__RELAXED(pushlock, saved_value, 0)) {
|
||||
semaphore_signal(&wait_block->semaphore);
|
||||
return;
|
||||
}
|
||||
|
||||
// there are multiple waiters now, so we have to iterate through the list
|
||||
__atomic_thread_fence(__ATOMIC_ACQUIRE);
|
||||
wait_block = PUSHLOCK_GET_POINTER(saved_value);
|
||||
}
|
||||
|
||||
while (wait_block->next->next)
|
||||
wait_block = wait_block->next;
|
||||
|
||||
pushlock_wait_block_t *to_wake = wait_block->next;
|
||||
wait_block->next = NULL;
|
||||
|
||||
while (!CAS_RELEASE__RELAXED(pushlock, saved_value, (saved_value & PUSHLOCK_MASK_POINTER_SHARED_COUNT) | PUSHLOCK_FLAGS_CONTENDED));
|
||||
|
||||
semaphore_signal(&to_wake->semaphore);
|
||||
}
|
||||
|
||||
static void pushlock_release_shared_contended(pushlock_t *pushlock, pushlock_t saved_value) {
|
||||
pushlock_wait_block_t *last_wait_block = PUSHLOCK_GET_POINTER(saved_value);
|
||||
pushlock_wait_block_t *penultimate_wait_block = NULL;
|
||||
if (last_wait_block->next) {
|
||||
penultimate_wait_block = last_wait_block;
|
||||
while (penultimate_wait_block->next->next)
|
||||
penultimate_wait_block = penultimate_wait_block->next;
|
||||
|
||||
last_wait_block = penultimate_wait_block->next;
|
||||
}
|
||||
|
||||
if (__atomic_sub_fetch(&last_wait_block->shared_count, 1, __ATOMIC_RELEASE))
|
||||
return;
|
||||
__atomic_thread_fence(__ATOMIC_ACQUIRE);
|
||||
|
||||
if (penultimate_wait_block == NULL) {
|
||||
if (CAS_RELEASE__RELAXED(pushlock, saved_value, 0)) {
|
||||
semaphore_signal(&last_wait_block->semaphore);
|
||||
return;
|
||||
}
|
||||
|
||||
__atomic_thread_fence(__ATOMIC_ACQUIRE);
|
||||
penultimate_wait_block = PUSHLOCK_GET_POINTER(saved_value);
|
||||
while (penultimate_wait_block->next->next)
|
||||
penultimate_wait_block = penultimate_wait_block->next;
|
||||
last_wait_block = penultimate_wait_block->next;
|
||||
}
|
||||
|
||||
penultimate_wait_block->next = NULL;
|
||||
|
||||
while (!CAS_RELEASE__RELAXED(pushlock, saved_value, (saved_value & PUSHLOCK_MASK_POINTER_SHARED_COUNT) | PUSHLOCK_FLAGS_CONTENDED));
|
||||
|
||||
semaphore_signal(&last_wait_block->semaphore);
|
||||
}
|
||||
|
||||
void pushlock_release_shared(pushlock_t *pushlock) {
|
||||
retry_fast_path:
|
||||
pushlock_t saved_value = PUSHLOCK_INCREMENT_SHARED_COUNT(PUSHLOCK_FLAGS_ACQUIRED);
|
||||
if (CAS_RELEASE__RELAXED(pushlock, saved_value, 0))
|
||||
return;
|
||||
|
||||
#ifdef DEBUG_LOCKS
|
||||
__assert(saved_value & PUSHLOCK_FLAGS_ACQUIRED);
|
||||
#endif
|
||||
if ((saved_value & PUSHLOCK_FLAGS_CONTENDED) == 0) {
|
||||
if ((saved_value & PUSHLOCK_FLAGS_EXCLUSIVE) == 0 && PUSHLOCK_GET_SHARED_COUNT(saved_value) > 1) {
|
||||
// shared lock with 2 or more holders, decrement shared count
|
||||
if (DO_CAS(pushlock, saved_value, PUSHLOCK_DECREMENT_SHARED_COUNT(saved_value)))
|
||||
return;
|
||||
} else {
|
||||
// shared lock with 1 holder or exclusive lock, can just set it to 0
|
||||
if (DO_CAS(pushlock, saved_value, 0))
|
||||
|
||||
if (saved_value & PUSHLOCK_FLAGS_EXCLUSIVE) {
|
||||
pushlock_release_exclusive(pushlock);
|
||||
return;
|
||||
}
|
||||
|
||||
continue;
|
||||
}
|
||||
|
||||
break;
|
||||
}
|
||||
|
||||
// lock is contended, we will have to go through the wait blocks and get the
|
||||
// last and penultimate ones
|
||||
bool skip_check = false;
|
||||
for (;;) {
|
||||
saved_value = *pushlock;
|
||||
pushlock_wait_block_t *prev = NULL, *last = PUSHLOCK_GET_POINTER(saved_value);
|
||||
#ifdef DEBUG_LOCKS
|
||||
__assert(last);
|
||||
#endif
|
||||
while (last->next != NULL) {
|
||||
prev = last;
|
||||
last = last->next;
|
||||
}
|
||||
|
||||
// return if its shared and we arent the only holder
|
||||
if (skip_check == false && (saved_value & PUSHLOCK_FLAGS_EXCLUSIVE) == 0 && __atomic_sub_fetch(&last->shared_count, 1, __ATOMIC_SEQ_CST) > 0)
|
||||
return;
|
||||
|
||||
skip_check = true;
|
||||
|
||||
// here we can be assured we are the only holder
|
||||
if (prev == NULL) {
|
||||
// last is being pointed to as the front, we just have to unset it
|
||||
if (DO_CAS(pushlock, saved_value, 0) == false)
|
||||
continue;
|
||||
} else {
|
||||
// we need to remove it from prev
|
||||
prev->next = NULL;
|
||||
// and unlock it properly, keeping in mind it still contended
|
||||
for (;;) {
|
||||
if (DO_CAS(pushlock, saved_value, (uintptr_t)PUSHLOCK_GET_POINTER(saved_value) | PUSHLOCK_FLAGS_CONTENDED))
|
||||
break;
|
||||
saved_value = *pushlock;
|
||||
}
|
||||
}
|
||||
|
||||
// wake the waiting thread
|
||||
semaphore_signal(&last->semaphore);
|
||||
if ((saved_value & PUSHLOCK_FLAGS_CONTENDED)) {
|
||||
__atomic_thread_fence(__ATOMIC_ACQUIRE);
|
||||
pushlock_release_shared_contended(pushlock, saved_value);
|
||||
return;
|
||||
}
|
||||
|
||||
if (!CAS_RELEASE__RELAXED(pushlock, saved_value, PUSHLOCK_DECREMENT_SHARED_COUNT(saved_value)))
|
||||
goto retry_fast_path;
|
||||
}
|
||||
|
||||
Reference in New Issue
Block a user