edfc5ab8b4
The scheduler queue locks could deadlock if the timer fired before the scoped lock destructor ran. Also, reduce lock contention by letting only one CPU steal work at a time.
104 lines
2.5 KiB
C++
104 lines
2.5 KiB
C++
#pragma once
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/// \file scheduler.h
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/// The task scheduler and related definitions
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#include <stdint.h>
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#include "kutil/spinlock.h"
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#include "kutil/vector.h"
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namespace kernel {
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namespace args {
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struct program;
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}}
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struct cpu_data;
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class lapic;
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class process;
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struct page_table;
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struct run_queue;
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/// The task scheduler
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class scheduler
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{
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public:
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/// Total number of priority levels
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static const uint8_t num_priorities = 8;
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/// Maximum (least urgent/interactive) priority
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static const uint8_t max_priority = num_priorities - 1;
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/// Default priority on process creation
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static const uint8_t default_priority = 1;
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/// Lowest (most urgent) priority achieved via promotion
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static const uint8_t promote_limit = 1;
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/// How long the base timer quantum is, in us
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static const uint64_t quantum_micros = 500;
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/// How many quanta a process gets before being rescheduled
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static const uint16_t process_quanta = 10;
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/// Constructor.
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/// \arg cpus The number of CPUs to schedule for
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scheduler(unsigned cpus);
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~scheduler();
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/// Create a new process from a program image in memory.
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/// \arg program The descriptor of the pogram in memory
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/// \returns The main thread of the loaded process
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thread * load_process(kernel::args::program &program);
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/// Create a new kernel task
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/// \arg proc Function to run as a kernel task
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/// \arg priority Priority to start the process with
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/// \arg constant True if this task cannot be promoted/demoted
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void create_kernel_task(
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void (*task)(),
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uint8_t priority,
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bool constant = false);
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/// Get the quantum for a given priority.
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static uint32_t quantum(int priority);
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/// Start the scheduler working. This may involve starting
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/// timer interrupts or other preemption methods.
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void start();
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/// Run the scheduler, possibly switching to a new task
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void schedule();
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/// Start scheduling a new thread.
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/// \arg t The new thread's TCB
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void add_thread(TCB *t);
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/// Get a reference to the scheduler
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/// \returns A reference to the global system scheduler
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static scheduler & get() { return *s_instance; }
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private:
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friend class process;
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static constexpr uint64_t promote_frequency = 10;
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static constexpr uint64_t steal_frequency = 10;
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void prune(run_queue &queue, uint64_t now);
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void check_promotions(run_queue &queue, uint64_t now);
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void steal_work(cpu_data &cpu);
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uint32_t m_next_pid;
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uint32_t m_tick_count;
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process *m_kernel_process;
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kutil::vector<run_queue> m_run_queues;
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// TODO: lol a real clock
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uint64_t m_clock = 0;
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unsigned m_steal_turn = 0;
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static scheduler *s_instance;
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};
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