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142
src/threads/thread.h
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142
src/threads/thread.h
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#ifndef THREADS_THREAD_H
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#define THREADS_THREAD_H
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#include <debug.h>
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#include <list.h>
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#include <stdint.h>
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/* States in a thread's life cycle. */
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enum thread_status
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{
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THREAD_RUNNING, /* Running thread. */
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THREAD_READY, /* Not running but ready to run. */
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THREAD_BLOCKED, /* Waiting for an event to trigger. */
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THREAD_DYING /* About to be destroyed. */
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};
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/* Thread identifier type.
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You can redefine this to whatever type you like. */
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typedef int tid_t;
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#define TID_ERROR ((tid_t) -1) /* Error value for tid_t. */
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/* Thread priorities. */
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#define PRI_MIN 0 /* Lowest priority. */
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#define PRI_DEFAULT 31 /* Default priority. */
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#define PRI_MAX 63 /* Highest priority. */
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/* A kernel thread or user process.
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Each thread structure is stored in its own 4 kB page. The
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thread structure itself sits at the very bottom of the page
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(at offset 0). The rest of the page is reserved for the
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thread's kernel stack, which grows downward from the top of
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the page (at offset 4 kB). Here's an illustration:
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4 kB +---------------------------------+
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| kernel stack |
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| V |
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| grows downward |
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+---------------------------------+
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| magic |
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| : |
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| : |
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| name |
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| status |
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0 kB +---------------------------------+
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The upshot of this is twofold:
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1. First, `struct thread' must not be allowed to grow too
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big. If it does, then there will not be enough room for
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the kernel stack. Our base `struct thread' is only a
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few bytes in size. It probably should stay well under 1
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kB.
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2. Second, kernel stacks must not be allowed to grow too
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large. If a stack overflows, it will corrupt the thread
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state. Thus, kernel functions should not allocate large
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structures or arrays as non-static local variables. Use
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dynamic allocation with malloc() or palloc_get_page()
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instead.
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The first symptom of either of these problems will probably be
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an assertion failure in thread_current(), which checks that
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the `magic' member of the running thread's `struct thread' is
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set to THREAD_MAGIC. Stack overflow will normally change this
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value, triggering the assertion. */
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/* The `elem' member has a dual purpose. It can be an element in
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the run queue (thread.c), or it can be an element in a
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semaphore wait list (synch.c). It can be used these two ways
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only because they are mutually exclusive: only a thread in the
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ready state is on the run queue, whereas only a thread in the
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blocked state is on a semaphore wait list. */
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struct thread
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{
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/* Owned by thread.c. */
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tid_t tid; /* Thread identifier. */
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enum thread_status status; /* Thread state. */
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char name[16]; /* Name (for debugging purposes). */
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uint8_t *stack; /* Saved stack pointer. */
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int priority; /* Priority. */
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struct list_elem allelem; /* List element for all threads list. */
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/* Shared between thread.c and synch.c. */
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struct list_elem elem; /* List element. */
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#ifdef USERPROG
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/* Owned by userprog/process.c. */
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uint32_t *pagedir; /* Page directory. */
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#endif
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/* Owned by thread.c. */
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unsigned magic; /* Detects stack overflow. */
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};
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/* If false (default), use round-robin scheduler.
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If true, use multi-level feedback queue scheduler.
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Controlled by kernel command-line option "mlfqs". */
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extern bool thread_mlfqs;
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void thread_init (void);
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void thread_start (void);
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size_t threads_ready(void);
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void thread_tick (void);
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void thread_print_stats (void);
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typedef void thread_func (void *aux);
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tid_t thread_create (const char *name, int priority, thread_func *, void *);
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void thread_block (void);
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void thread_unblock (struct thread *);
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struct thread *thread_current (void);
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tid_t thread_tid (void);
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const char *thread_name (void);
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void thread_exit (void) NO_RETURN;
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void thread_yield (void);
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/* Performs some operation on thread t, given auxiliary data AUX. */
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typedef void thread_action_func (struct thread *t, void *aux);
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void thread_foreach (thread_action_func *, void *);
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int thread_get_priority (void);
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void thread_set_priority (int);
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int thread_get_nice (void);
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void thread_set_nice (int);
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int thread_get_recent_cpu (void);
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int thread_get_load_avg (void);
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#endif /* threads/thread.h */
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