Al's cosmetic rearrangement
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Ben Gras
parent
50951c50f9
commit
cc3201bacd
1 changed files with 39 additions and 51 deletions
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@ -1,17 +1,17 @@
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/* The file contains the clock task, which handles all time related functions.
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* Important events that are handled by the CLOCK include alarm timers and
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* (re)scheduling user processes.
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/* This file contains the clock task, which handles time related functions.
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* Important events that are handled by the CLOCK include setting and
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* monitoring alarm timers and deciding when to (re)schedule processes.
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* The CLOCK offers a direct interface to kernel processes. System services
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* can access its services through system calls, such as sys_setalarm(). The
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* CLOCK task thus is hidden for the outside world.
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* CLOCK task thus is hidden from the outside world.
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*
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* Changes:
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* Oct 08, 2005 reordering and comment editing (A. S. Woodhull)
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* Mar 18, 2004 clock interface moved to SYSTEM task (Jorrit N. Herder)
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* Sep 30, 2004 source code documentation updated (Jorrit N. Herder)
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* Sep 24, 2004 redesigned alarm timers (Jorrit N. Herder)
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*
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* The function do_clocktick() is only triggered by the clock's interrupt
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* The function do_clocktick() is triggered by the clock's interrupt
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* handler when a watchdog timer has expired or a process must be scheduled.
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*
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* In addition to the main clock_task() entry point, which starts the main
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@ -24,7 +24,7 @@
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*
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* (+) The CLOCK task keeps tracks of watchdog timers for the entire kernel.
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* The watchdog functions of expired timers are executed in do_clocktick().
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* It is crucial that watchdog functions cannot block, or the CLOCK task may
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* It is crucial that watchdog functions not block, or the CLOCK task may
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* be blocked. Do not send() a message when the receiver is not expecting it.
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* Instead, notify(), which always returns, should be used.
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*/
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@ -40,7 +40,6 @@ FORWARD _PROTOTYPE( int clock_handler, (irq_hook_t *hook) );
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FORWARD _PROTOTYPE( int do_clocktick, (message *m_ptr) );
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/* Clock parameters. */
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#if (CHIP == INTEL)
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#define COUNTER_FREQ (2*TIMER_FREQ) /* counter frequency using square wave */
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#define LATCH_COUNT 0x00 /* cc00xxxx, c = channel, x = any */
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#define SQUARE_WAVE 0x36 /* ccaammmb, a = access, m = mode, b = BCD */
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@ -49,14 +48,9 @@ FORWARD _PROTOTYPE( int do_clocktick, (message *m_ptr) );
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#define TIMER_FREQ 1193182L /* clock frequency for timer in PC and AT */
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#define CLOCK_ACK_BIT 0x80 /* PS/2 clock interrupt acknowledge bit */
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#endif
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#if (CHIP == M68000)
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#define TIMER_FREQ 2457600L /* timer 3 input clock frequency */
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#endif
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/* The CLOCK's timers queue. The functions in <timers.h> operate on this.
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* All system processes possess a single synchronous alarm timer. If other
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* Each system process possesses a single synchronous alarm timer. If other
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* kernel parts want to use additional timers, they must declare their own
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* persistent (static) timer structure, which can be passed to the clock
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* via (re)set_timer().
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@ -74,15 +68,14 @@ PRIVATE irq_hook_t clock_hook; /* interrupt handler hook */
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*===========================================================================*/
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PUBLIC void clock_task()
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{
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/* Main program of clock task. It determines which call this is by looking at
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* the message type and dispatches.
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/* Main program of clock task. If the call is not HARD_INT it is an error.
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*/
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message m; /* message buffer for both input and output */
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int result; /* result returned by the handler */
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init_clock(); /* initialize clock task */
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/* Main loop of the clock task. Get work, process it, sometimes reply. */
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/* Main loop of the clock task. Get work, process it. Never reply. */
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while (TRUE) {
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/* Go get a message. */
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@ -112,7 +105,7 @@ message *m_ptr; /* pointer to request message */
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/* A process used up a full quantum. The interrupt handler stored this
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* process in 'prev_ptr'. First make sure that the process is not on the
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* scheduling queues. Then announce the process ready again. Since it has
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* no more time left, it will get a new quantum and inserted at the right
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* no more time left, it gets a new quantum and is inserted at the right
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* place in the queues. As a side-effect a new process will be scheduled.
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*/
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if (prev_ptr->p_ticks_left <= 0 && priv(prev_ptr)->s_flags & PREEMPTIBLE) {
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@ -131,6 +124,33 @@ message *m_ptr; /* pointer to request message */
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return(EDONTREPLY);
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}
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/*===========================================================================*
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* init_clock *
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*===========================================================================*/
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PRIVATE void init_clock()
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{
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/* Initialize the CLOCK's interrupt hook. */
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clock_hook.proc_nr = CLOCK;
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/* Initialize channel 0 of the 8253A timer to, e.g., 60 Hz. */
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outb(TIMER_MODE, SQUARE_WAVE); /* set timer to run continuously */
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outb(TIMER0, TIMER_COUNT); /* load timer low byte */
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outb(TIMER0, TIMER_COUNT >> 8); /* load timer high byte */
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put_irq_handler(&clock_hook, CLOCK_IRQ, clock_handler);/* register handler */
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enable_irq(&clock_hook); /* ready for clock interrupts */
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}
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/*===========================================================================*
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* clock_stop *
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*===========================================================================*/
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PUBLIC void clock_stop()
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{
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/* Reset the clock to the BIOS rate. (For rebooting) */
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outb(TIMER_MODE, 0x36);
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outb(TIMER0, 0);
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outb(TIMER0, 0);
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}
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/*===========================================================================*
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* clock_handler *
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*===========================================================================*/
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@ -186,7 +206,7 @@ irq_hook_t *hook;
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}
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/* Check if do_clocktick() must be called. Done for alarms and scheduling.
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* Even the clock and system tasks get finite, but large, quanta.
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* Some processes, such as the kernel tasks, cannot be preempted.
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*/
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if ((next_timeout <= realtime) || (proc_ptr->p_ticks_left <= 0)) {
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prev_ptr = proc_ptr; /* store running process */
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@ -234,35 +254,6 @@ struct timer *tp; /* pointer to timer structure */
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TMR_NEVER : clock_timers->tmr_exp_time;
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}
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#if (CHIP == INTEL)
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/*===========================================================================*
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* init_clock *
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*===========================================================================*/
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PRIVATE void init_clock()
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{
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/* Initialize the CLOCK's interrupt hook. */
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clock_hook.proc_nr = CLOCK;
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/* Initialize channel 0 of the 8253A timer to, e.g., 60 Hz. */
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outb(TIMER_MODE, SQUARE_WAVE); /* set timer to run continuously */
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outb(TIMER0, TIMER_COUNT); /* load timer low byte */
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outb(TIMER0, TIMER_COUNT >> 8); /* load timer high byte */
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put_irq_handler(&clock_hook, CLOCK_IRQ, clock_handler);/* register handler */
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enable_irq(&clock_hook); /* ready for clock interrupts */
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}
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/*===========================================================================*
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* clock_stop *
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*===========================================================================*/
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PUBLIC void clock_stop()
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{
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/* Reset the clock to the BIOS rate. (For rebooting) */
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outb(TIMER_MODE, 0x36);
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outb(TIMER0, 0);
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outb(TIMER0, 0);
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}
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/*===========================================================================*
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* read_clock *
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*===========================================================================*/
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@ -281,6 +272,3 @@ PUBLIC unsigned long read_clock()
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return count;
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}
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#endif /* (CHIP == INTEL) */
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