08time/time

   1 %Time Management
   2 %Thadeu Cascardo
   3
   4 # Tickes, Jiffies
   5
   6 * The timer ticks with a frequency, interrupting the system
   7 * Necessary for preemptive scheduling, using a time slice
   8 * Linux counts the number of ticks in the *jiffies* variable
   9 * It's interrupted *HZ* times in a second
  10
  11 # Busy waiting
  12
  13 * time\\_after
  14 * time\\_before
  15 * cpu\\_relax
  16 * udelay
  17
  18 # Scheduling
  19
  20 * schedule
  21 * set\\_current\\_state
  22 * TASK\\_INTERRUPTIBLE
  23 * TASK\\_UNINTERRUPTIBLE
  24 * TASK\\_RUNNING
  25 * schedule\\_timeout
  26 * schedule\\_timeout\\_interruptible
  27 * msleep
  28 * msleep\\_interruptible
  29
  30 # Timers
  31
  32 * linux/timer.h
  33 * struct timer\\_list
  34         - unsigned long expires
  35         - void function(unsigned long)
  36         - unsigned long data
  37 * init\\_timer
  38 * TIMER\\_INITIALIZER
  39 * add\\_timer
  40 * del\\_timer
  41 * mod\\_timer
  42 * del\\_timer\\_sync
  43
  44 # Work queues
  45
  46 * Queues of functions to be called in a kernel thread
  47 * They execute in process context, so they may sleep
  48 * However, accessing user space memory does not make sense here
  49 * Works should not take long or they will delay other works execution
  50 * There's a default workqueue, keventd or events
  51
  52 # Works
  53
  54 * include linux/workqueue.h
  55 * struct work\\_struct
  56 * DECLARE\\_WORK(name, func)
  57 * INIT\\_WORK(work, func)
  58 * queue\\_work(wq, work)
  59 * schedule\\_work(work)
  60 * flush\\_work(work)
  61 * cancel\\_work\\_sync(work)
  62
  63 # Delayed work
  64
  65 * struct delayed\\_work
  66 * DECLARE\\_DELAYED\\_WORK(name, func)
  67 * INIT\\_DELAYED\\_WORK(dwork, func)
  68 * queue\\_delayed\\_work(wq, dwork, delay)
  69 * schedule\\_delayed\\_work(dwork, delay)
  70 * flush\\_delayed\\_work(dwork)
  71 * cancel\\_delayed\\_work(dwork)
  72 * cancel\\_delayed\\_work\\_sync(dwork)
  73
  74 # Workqueue
  75
  76 * create\\_workqueue(name)
  77 * create\\_singlethread\\_workqueue(name)
  78 * destroy\\_workqueue(wq)
  79 * flush\\_workqueue(wq)
  80 * flush\\_scheduled\\_work()
  81
  82 # Tasklets
  83
  84 * include linux/interrupt.h
  85 * struct tasklet\\_struct
  86 * DECLARE\\_TASKLET(name, func, data)
  87 * tasklet\\_init(tsk, func, data)
  88 * tasklet\\_schedule
  89 * tasklet\\_hi\\_schedule
  90 * tasklet\\_enable
  91 * tasklet\\_disable
  92 * tasklet\\_kill
  93
  94 # Completion
  95
  96 * include linux/completion.h
  97 * struct completion
  98 * DECLARE\\_COMPLETION(name)
  99 * init\\_completion(comp)
 100 * wait\\_for\\_completion(comp)
 101 * wait\\_for\\_completion\\_interruptible
 102 * wait\\_for\\_completion\\_timeout
 103 * complete
 104
 105 # Wait queue
 106
 107 * include linux/wait.h
 108 * wait\\_queue\\_head\\_t
 109 * DECLARE\\_WAIT\\_QUEUE\\_HEAD(name)
 110 * init\\_waitqueue\\_head(wqh)
 111 * wake\\_up(wqh)
 112 * wait\\_event(wqh, cond)
 113 * wait\\_event\\_timeout(wqh, cond, timeout)
 114 * wait\\_event\\_interruptible(wqh, cond)