72 lines
2.5 KiB
C
72 lines
2.5 KiB
C
// ke_semaphore.c - counting semaphore
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#include <stdbool.h>
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#include <kernel/ke_semaphore.h>
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#include <kernel/ke_thread.h>
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#include <kernel/ke_sched.h>
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#include <kernel/ke_irql.h>
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#include <kernel/ob_object.h>
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static void KiSemaphoreDestroy(OBJECT* obj) { (void)obj; }
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__declspec(dllexport) KSTATUS KeSemaphoreCreate(int32_t initial, int32_t max, SEMAPHORE **out) {
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if (!out || initial < 0 || max < 1 || initial > max)
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return STATUS_INVALID_PARAMETER;
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SEMAPHORE* s = (SEMAPHORE *)ObAllocateObject(ObjectTypeSemaphore, sizeof(SEMAPHORE));
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if (!s) return STATUS_NO_MEMORY;
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s->Header.Destroy = KiSemaphoreDestroy;
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s->Lock = (SPINLOCK)SPINLOCK_INIT;
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s->Count = initial;
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s->MaxCount = max;
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LIST_INIT(&s->WaitList);
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*out = s;
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return STATUS_SUCCESS;
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}
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__declspec(dllexport) KSTATUS KeWaitSemaphore(SEMAPHORE* sem) {
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if (!sem) return STATUS_INVALID_PARAMETER;
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if (!KeCanWait()) return STATUS_INVALID_IRQL;
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THREAD* self = KeGetCurrentThread();
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uintptr_t flags = KeAcquireSpinlock(&sem->Lock);
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if (sem->Count > 0) {
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sem->Count--;
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KeReleaseSpinlock(&sem->Lock, flags);
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return STATUS_SUCCESS;
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}
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KePrepareBlockThread(self, &sem->Header, 0);
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ListInsertTail(&sem->WaitList, &self->SchedulerLink);
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KeSetThreadWaitList(self, &sem->WaitList);
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KeReleaseSpinlock(&sem->Lock, flags);
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return KeCommitBlockThread(self, 0);
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}
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__declspec(dllexport) KSTATUS KeTrySemaphore(SEMAPHORE* sem) {
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if (!sem) return STATUS_INVALID_PARAMETER;
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uintptr_t flags = KeAcquireSpinlock(&sem->Lock);
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if (sem->Count > 0) {
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sem->Count--;
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KeReleaseSpinlock(&sem->Lock, flags);
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return STATUS_SUCCESS;
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}
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KeReleaseSpinlock(&sem->Lock, flags);
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return STATUS_FAILURE;
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}
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__declspec(dllexport) void KeSignalSemaphore(SEMAPHORE* sem) {
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if (!sem) return;
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uintptr_t flags = KeAcquireSpinlock(&sem->Lock);
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if (!LIST_IS_EMPTY(&sem->WaitList)) {
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// Transfer this semaphore release directly to the selected waiter. The
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// count stays unchanged; the waiter returns success without looping and
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// consuming a count later.
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LIST_ENTRY* node = ListPopHead(&sem->WaitList);
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THREAD* waiter = CONTAINING_RECORD(node, THREAD, SchedulerLink);
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KeReleaseSpinlock(&sem->Lock, flags);
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KeUnblockThreadWithStatus(waiter, STATUS_SUCCESS);
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return;
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}
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if (sem->Count < sem->MaxCount) sem->Count++;
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KeReleaseSpinlock(&sem->Lock, flags);
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}
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