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@ -12,11 +12,6 @@
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#warning "CONFIG_SCHED_MAXTASK is > 64, this could have a significant performance impact"
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#endif
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#ifndef CONFIG_STACKSZ
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/** Per-task stack size in bytes */
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#define CONFIG_STACKSZ 4096U
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#endif
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enum task_state {
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/** Task is dead / doesn't exist */
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TASK_DEAD,
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@ -24,60 +19,84 @@ enum task_state {
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TASK_READY,
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/** Task is waiting for its next time share. */
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TASK_QUEUE,
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/** Task is sleeping, `sleep_until` specifies when to wake it up. */
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/** Task is sleeping, `task::sleep` specifies for how many ticks. */
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TASK_SLEEP,
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/** Task is waiting for I/O to flush buffers. */
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TASK_IOWAIT,
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};
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/** Stores an entire process image. */
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/** @brief Core structure holding information about a task. */
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struct task {
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struct kent kent;
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/** current stack pointer (only gets updated for task switching) */
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void *sp;
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/** first address of the stack (highest if the stack grows downwards) */
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void *stack_bottom;
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/** if `state` is `TASK_SLEEP`, the last execution time */
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unsigned long int lastexec;
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/** if `state` is `TASK_SLEEP`, the amount of us to sleep in total */
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unsigned long int sleep_usecs;
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/** @brief If state is `TASK_SLEEP`, the total amount of ticks to sleep */
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unsigned long int sleep;
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/** @brief Last execution in ticks */
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unsigned long int last_tick;
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enum task_state state;
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pid_t pid;
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};
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/** @brief Current task (access from syscall context only) */
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extern struct task *current;
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/** @brief Global system tick counter (may overflow) */
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extern volatile unsigned long int tick;
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/**
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* @brief If nonzero, the scheduler is invoked after the current syscall.
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* This is checked and then cleared after every syscall. If it has a nonzero
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* value, `sched_switch()` is called after `arch_enter()`.
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*/
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extern int need_resched;
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/**
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* Initialize the scheduler subsystem.
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* @brief Initialize the scheduler subsystem.
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* This sets up a hardware interrupt timer (SysTick for Cortex-M3).
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*/
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int sched_init(void);
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/**
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* Switch to the next task (interrupt context only).
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* @brief Switch to the next task (scheduler context only).
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* Must be called directly from within an interrupt routine.
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* This selects a new task to be run and updates the old and new task's `state`
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* field to the appropriate value.
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* field to the appropriate value. Called from the scheduler exception handler.
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*
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* @param curr_sp: stack pointer of the current task
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* @returns stack pointer of the new task
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* @param curr_sp Stack pointer of the current task
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* @returns Stack pointer of the new task
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*/
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void *sched_switch(void *curr_sp);
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/**
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* Create a copy of the current process image and return it.
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* @brief Create a copy of the `current` task and return it.
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* The new task becomes a child of the `current` task and is inserted into the
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* process table so that it can be executed by the scheduler after its state
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* is set to `TASK_QUEUE`. When the task is returned, its initial state is
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* `TASK_UNKNOWN` so that the caller has time to do any additional required
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* setup work.
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*
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* @param task Task to make a copy of
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* @returns The new (child) task copy, or `NULL` on failure
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*/
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struct task *task_clone(struct task *task);
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/**
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* @brief Sleep for an approximate amount of milliseconds.
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* Must not be invoked from atomic or irq context.
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*
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* @param task: the task to make a copy of
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* @returns the new (child) task copy, or `NULL` on failure
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* @param ms Amount of milliseconds
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*/
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struct task *sched_task_clone(struct task *task);
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void msleep(unsigned long int ms);
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/**
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* Request the scheduler be invoked early, resulting in the current task to
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* be suspended.
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* @brief Suspend the `current` task and invoke the scheduler early.
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* May only be called from syscall context.
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*
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* @param state: State the task should enter.
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* @param state State the task should enter.
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* Allowed values are `TASK_SLEEP` and `TASK_IOWAIT`.
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*/
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void yield(enum task_state state);
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