KERNEL OBJECTS - THREADS

Threads can be thought of as virtual CPUs. The module that processes them is oz_knl_thread.c.

Each thread has the following properties:

• unique id number
• state (initializing, running, waiting for cpu, waiting for event(s), zombie)
• what thread it's parent is, and what threads are its children
• time in each of the states
• amount of run time left before scheduling demotion
• amount of wait time left before scheduling promotion
• base and current execution priority
• process it belongs to
• event flags it is waiting for (if in waiting for event(s) state)
• ast modes for each processor mode (inhibited or enabled)
• ast queue for each processor mode
• exit handlers for each processor mode
• which cpu (if any) it's context is loaded in
• initialize, exit, suspend event flags
• wake status, indicates why the thread was woken from wait state
• exit status, and whether or not it has exited
• reference count (thread gets deleted when this goes zero)
• security keys (what the thread can access)
• security attributes (who can access the thread)
• pending I/O requests (they get aborted when thread exits)
• thread-private smplock
• name
• hardware context (saved registers, stack pointer, etc), only valid when not loaded in a physical cpu

These methods are defined:

• oz_knl_thread_abort - abort a thread (force it to exit)
• oz_knl_thread_changeproc - change current thread's process
• oz_knl_thread_chkpendast - see if current thread has pending ast's at a given processor mode
• oz_knl_thread_count - count number of threads in a process
• oz_knl_thread_cpuinit - used at boot time only to make the cpu into a thread
• oz_knl_thread_create - create a new thread and queue it for execution
• oz_knl_thread_deqast - dequeue an ast (if any) from current thread at given processor mode
• oz_knl_thread_exit - exit (terminate) current thread
• oz_knl_thread_gettis - get a thread's time in a given state
• oz_knl_thread_getbasepri - get a thread's base execution priority
• oz_knl_thread_getbyid - get a thread given its id number
• oz_knl_thread_getcur - get the thread that's executing on current cpu
• oz_knl_thread_getcurprio - get a thread's current execution priority
• oz_knl_thread_getexitevent - get thread's exit event flag (if any)
• oz_knl_thread_getexitsts - get thread's exit status (and whether it has exited or not)
• oz_knl_thread_getid - get thread's id number
• oz_knl_thread_getname - get thread's name string
• oz_knl_thread_getnext - get first/next thread in a process
• oz_knl_thread_getprocess - get a thread's process
• oz_knl_thread_getwevent - get event flag(s) the thread is waiting for (if any)
• oz_knl_thread_getsecattr - get a thread's security attributes
• oz_knl_thread_getseckeys - get a thread's security keys
• oz_knl_thread_getstate - get a thread's current state
• oz_knl_thread_inccurprio - increment/decrement a thread's current execution priority
• oz_knl_thread_increfc - increment/decrement thread reference count
• oz_knl_thread_wait - put current thread into a particular wait state
• oz_knl_thread_orphan - orphan a thread so it doesn't get aborted/suspended when its parent does
• oz_knl_thread_queueast - queue ast to thread
• oz_knl_thread_resume - resume a thread and all its children
• oz_knl_thread_setast - set current thread's ast delivery mode for a particular process mode
• oz_knl_thread_setbasepri - set a thread's base execution priority
• oz_knl_thread_setcurprio - set a thread's current execution priority
• oz_knl_thread_setdefcresecattr - set a thread's default create security attributes (who can access what it creates)
• oz_knl_thread_setsecattr - set a thread's security attributes (who can access it)
• oz_knl_thread_setseckeys - set a thread's security keys (what it can access)
• oz_knl_thread_suspend - suspend a thread and all its children
• oz_knl_thread_wakewev - wake a thread from wait-for-event state

Exit handlers are closely related so are included in oz_knl_thread.c. They are called when a thread exits. There is an exit handler queue for each processor mode.

• oz_knl_exhand_create - set up an handler to be called when the thread exits
• oz_knl_exhand_delete - delete an exit handler from a thread
• oz_knl_exhand_dequeue - dequeue an exit handler from a thread