diff options
| author | Steven Le Rouzic <steven.lerouzic@gmail.com> | 2024-06-02 00:26:57 +0200 |
|---|---|---|
| committer | Steven Le Rouzic <steven.lerouzic@gmail.com> | 2024-06-02 00:26:57 +0200 |
| commit | 45f420a338ea02225bb8a98c9aca5eed8d6a23ae (patch) | |
| tree | 97fdb1c8e81ba79b101b928158e5e37fa938c8f3 /kernel/spinlock.c | |
Initial commit
Diffstat (limited to 'kernel/spinlock.c')
| -rw-r--r-- | kernel/spinlock.c | 77 |
1 files changed, 77 insertions, 0 deletions
diff --git a/kernel/spinlock.c b/kernel/spinlock.c new file mode 100644 index 0000000..8f9c654 --- /dev/null +++ b/kernel/spinlock.c @@ -0,0 +1,77 @@ +#include "kernel/spinlock.h"
+#include "kernel/cpu.h"
+#include "kernel/riscv.h"
+#include "kernel/atomic.h"
+
+#define NO_CPU 0xffff'ffff
+
+static bool current_cpu_holding(const Spinlock* lock)
+{
+ return lock->locking == current_cpu()->id;
+}
+
+static void push_intr_off()
+{
+ Cpu* cpu = current_cpu();
+
+ bool old_intr_enabled = (rc_sstatus(SSTATUS_SIE) & SSTATUS_SIE) != 0;
+ if (cpu->intr_off_count == 0)
+ {
+ cpu->intr_enabled_before_off = old_intr_enabled;
+ }
+
+ cpu->intr_off_count += 1;
+}
+
+static void pop_intr_off()
+{
+ Cpu* cpu = current_cpu();
+
+ if (cpu->intr_off_count == 0)
+ {
+ panic("pop_intr_off: count = 0");
+ }
+
+ cpu->intr_off_count -= 1;
+ if (cpu->intr_off_count == 0 && cpu->intr_enabled_before_off)
+ {
+ s_sstatus(SSTATUS_SIE);
+ }
+}
+
+void spinlock_init(Spinlock* lock)
+{
+ lock->next_ticket = 0;
+ lock->serving = 0;
+ lock->locking = NO_CPU;
+}
+
+void spinlock_acquire(Spinlock* lock)
+{
+ if (current_cpu_holding(lock))
+ {
+ panic("spinlock_acquire: already held");
+ }
+
+ push_intr_off();
+
+ uint32_t ticket = atomic_fetch_add(&lock->next_ticket, 1, MEM_RELAXED);
+
+ while (atomic_load(&lock->serving, MEM_RELAXED) != ticket) {}
+ atomic_fence(MEM_ACQUIRE);
+
+ lock->locking = current_cpu()->id;
+}
+
+void spinlock_release(Spinlock* lock)
+{
+ if (!current_cpu_holding(lock))
+ {
+ panic("spinlock_release: not held");
+ }
+
+ lock->locking = NO_CPU;
+ atomic_fetch_add(&lock->serving, 1, MEM_RELEASE);
+
+ pop_intr_off();
+}
|