78 lines
1.6 KiB
C
78 lines
1.6 KiB
C
#include "kernel/spinlock.h"
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#include "kernel/cpu.h"
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#include "kernel/riscv.h"
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#include "kernel/atomic.h"
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#define NO_CPU 0xffff'ffff
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static bool current_cpu_holding(const Spinlock* lock)
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{
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return lock->locking == current_cpu()->id;
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}
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static void push_intr_off()
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{
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Cpu* cpu = current_cpu();
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bool old_intr_enabled = (rc_sstatus(SSTATUS_SIE) & SSTATUS_SIE) != 0;
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if (cpu->intr_off_count == 0)
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{
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cpu->intr_enabled_before_off = old_intr_enabled;
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}
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cpu->intr_off_count += 1;
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}
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static void pop_intr_off()
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{
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Cpu* cpu = current_cpu();
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if (cpu->intr_off_count == 0)
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{
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panic("pop_intr_off: count = 0");
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}
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cpu->intr_off_count -= 1;
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if (cpu->intr_off_count == 0 && cpu->intr_enabled_before_off)
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{
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s_sstatus(SSTATUS_SIE);
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}
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}
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void spinlock_init(Spinlock* lock)
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{
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lock->next_ticket = 0;
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lock->serving = 0;
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lock->locking = NO_CPU;
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}
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void spinlock_acquire(Spinlock* lock)
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{
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if (current_cpu_holding(lock))
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{
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panic("spinlock_acquire: already held");
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}
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push_intr_off();
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uint32_t ticket = atomic_fetch_add(&lock->next_ticket, 1, MEM_RELAXED);
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while (atomic_load(&lock->serving, MEM_RELAXED) != ticket) {}
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atomic_fence(MEM_ACQUIRE);
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lock->locking = current_cpu()->id;
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}
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void spinlock_release(Spinlock* lock)
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{
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if (!current_cpu_holding(lock))
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{
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panic("spinlock_release: not held");
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}
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lock->locking = NO_CPU;
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atomic_fetch_add(&lock->serving, 1, MEM_RELEASE);
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pop_intr_off();
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}
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