slkern/sched.h

// This is NEW CODE a header to interact with the scheduler
#ifndef _SCHED_H
#define _SCHED_H

// The size of one register on the processor.
typedef unsigned long long sched_reg_t;

// The context saved between scheduler states must match EXACTLY the one in
// sched_switchcontext (see schedasm.S). This only needs to save the kernel's
// C-like execution state.
typedef struct sched_context sched_context_t;

struct sched_context {
  // WARNING: REMEMBER TO CHANGE schedasm.S if this ordering is modified!
  sched_reg_t s0;
  sched_reg_t s1;
  sched_reg_t s2;
  sched_reg_t s3;
  sched_reg_t s4;
  sched_reg_t s5;
  sched_reg_t s6;
  sched_reg_t s7;
  sched_reg_t s8;
  sched_reg_t s9;
  sched_reg_t s10;
  sched_reg_t s11;
  sched_reg_t ra;
  sched_reg_t sp;
};

// Trap frame used by the trampoline code (currently being migrated to
// new code)
// Data for each process is stored in the page below the user's
// trampoline code, but will be at an arbitrary address in kernel-mode
// (TODO: Better mapping for multithreading?).
// This is currently saved/restored by the old xv6 code so will be
// rearranged a bit as that is migrated (for now it should mostly match
// the old layout but with new types).
// See notes in trampoline.S
typedef struct sched_frame sched_frame_t;

struct sched_frame {
  // Offset 0:
  sched_reg_t kmode_satp;    // Kernel-mode page table
  sched_reg_t kmode_sp;      // Kernel-mode stack pointer
  sched_reg_t kmode_trap;    // Address of usertrap() function or similar
  sched_reg_t epc;            // User-mode program counter
  // Offset 32:
  sched_reg_t kmode_hartid;  // Kernel-mode thread pointer register
  sched_reg_t ra;
  sched_reg_t sp;
  sched_reg_t gp;
  // Offset 64:
  sched_reg_t tp;
  sched_reg_t t0;
  sched_reg_t t1;
  sched_reg_t t2;
  // Offset 96
  sched_reg_t s0;
  sched_reg_t s1;
  sched_reg_t a0;
  sched_reg_t a1;
  // Offset 128
  sched_reg_t a2;
  sched_reg_t a3;
  sched_reg_t a4;
  sched_reg_t a5;
  // Offset 160
  sched_reg_t a6;
  sched_reg_t a7;
  sched_reg_t s2;
  sched_reg_t s3;
  // Offset 192
  sched_reg_t s4;
  sched_reg_t s5;
  sched_reg_t s6;
  sched_reg_t s7;
  // Offset 224:
  sched_reg_t s8;
  sched_reg_t s9;
  sched_reg_t s10;
  sched_reg_t s11;
  // Offset 256:
  sched_reg_t t3;
  sched_reg_t t4;
  sched_reg_t t5;
  sched_reg_t t6;
};


// Switches context by storing registers into oldstruct and loading different
// values from newstruct, then returns oldstruct as a value to the new context.
sched_context_t* sched_switchcontext(sched_context_t* oldstruct, sched_context_t* newstruct);

// Each CPU core is referred to as "core" in this system, since there may be a
// need to represent more complex topologies with multiple clusters of multiple
// cores etc. where each layer would otherwise all be confusable for "CPUs".
// A CPU core is defined as physical or virtual hardware implementing 1 main
// thread of execution.
typedef struct sched_core sched_core_t;

// Spinlocks are still mostly implemented by old code but are defined here
// due to being tightly integrated into the scheduler.
typedef struct sched_spinlock sched_spinlock_t;

struct sched_spinlock {
  int lockvar;
  int padding;
  char* debugstring; // Name for debugging
  sched_core_t* core; // The CPU core that's using this lock
};

typedef struct sched_sleeplock sched_sleeplock_t;

struct sched_sleeplock {
  unsigned int islocked;
  int padding;
  sched_spinlock_t spin; // The spinlock used internally
  int pid; // The process id of the waiting process
  char* debugstring; // Name for debugging (TODO: This is kind of redundant as spinlock has a debugstring already.
};

struct sched_core {
  struct proc* process;
  sched_context_t registers;
  int preempted;
  int allowstarvation;
  int interruptsoff_depth;
  int interruptsoff_wereinterruptson;
};

#define SCHED_CORE_MAX 64

extern sched_core_t sched_cores[SCHED_CORE_MAX];

// These are implemented in schedasm.S
sched_reg_t sched_cputhreadpointer_get();
void sched_cputhreadpointer_set(sched_reg_t value);

// Returns the core number, can't be called with interrupts enabled in case process is rescheduled
#define SCHED_CORE_THISNUMBER_NOINTERRUPTS() \
  ((int)sched_cputhreadpointer_get())

// Returns this core's sched_core_t*, can't be called with interrupts enabled in case process is rescheduled
#define SCHED_CORE_THIS_NOINTERRUPTS() \
  (&sched_cores[SCHED_CORE_THISNUMBER_NOINTERRUPTS()])

typedef int sched_state_t;

#define SCHED_STATE_UNUSED        ((sched_state_t)0)
#define SCHED_STATE_USED          ((sched_state_t)1)
#define SCHED_STATE_SLEEPING      ((sched_state_t)2)
#define SCHED_STATE_RUNNABLE      ((sched_state_t)3)
#define SCHED_STATE_RUNNING       ((sched_state_t)4)
#define SCHED_STATE_ZOMBIE        ((sched_state_t)5)

void sched_restate_alreadylocked(struct proc* p, sched_state_t s);

typedef struct sched_task sched_task_t;
typedef struct sched_thread sched_thread_t;

extern int timeslice_min;
extern int timeslice_max;

void sched_wake(void* pointer);

void sched_dumpstatus(); // Dump scheduler information to console.

// From ifndef at top of file:
#endif