198c976f7e
that passes signal map along. This mechanisms is also used for nonuser signals like SIGKMESS, SIGKSTOP, SIGKSIG. Revised comments of many system call handlers. Renamed setpriority to nice.
305 lines
11 KiB
C
Executable file
305 lines
11 KiB
C
Executable file
/* The file contais 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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* 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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*
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* Changes:
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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 timers and alarms (Jorrit N. Herder)
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*
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* The function do_clocktick() is not triggered from the clock library, but
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* by the clock's interrupt handler when a watchdog timer has expired or
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* another user 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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* loop, there are several other minor entry points:
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* clock_stop: called just before MINIX shutdown
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* get_uptime: get realtime since boot in clock ticks
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* set_timer: set a watchdog timer (*, see note below!)
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* reset_timer: reset a watchdog timer (*)
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* calc_elapsed: do timing measurements: get delta ticks and pulses
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* read_clock: read the counter of channel 0 of the 8253A timer
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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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* 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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#include "kernel.h"
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#include "proc.h"
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#include <signal.h>
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#include <minix/com.h>
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/* Function prototype for PRIVATE functions. */
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FORWARD _PROTOTYPE( void init_clock, (void) );
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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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/* 11x11, 11 = LSB then MSB, x11 = sq wave */
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#define TIMER_COUNT ((unsigned) (TIMER_FREQ/HZ)) /* initial value for counter*/
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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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* 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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* When a timer expires its watchdog function is run by the CLOCK task.
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*/
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PRIVATE timer_t *clock_timers; /* queue of CLOCK timers */
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PRIVATE clock_t next_timeout; /* realtime that next timer expires */
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/* The time is incremented by the interrupt handler on each clock tick. */
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PRIVATE clock_t realtime; /* real time clock */
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PRIVATE irq_hook_t clock_hook; /* interrupt handler hook */
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/*===========================================================================*
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* clock_task *
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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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*/
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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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while (TRUE) {
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/* Go get a message. */
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receive(ANY, &m);
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/* Handle the request. */
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switch (m.m_type) {
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case HARD_INT:
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result = do_clocktick(&m); /* handle clock tick */
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break;
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default: /* illegal message type */
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kprintf("Warning, illegal CLOCK request from %d.\n", m.m_source);
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result = EBADREQUEST;
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}
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/* Send reply, unless inhibited, e.g. by do_clocktick(). Use the kernel
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* function lock_send() to prevent a system call trap. The destination
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* is known to be blocked waiting for a message.
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*/
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if (result != EDONTREPLY) {
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m.m_type = result;
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if (OK != lock_send(m.m_source, &m))
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kprintf("Warning, CLOCK couldn't reply to %d.\n", m.m_source);
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}
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}
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}
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/*===========================================================================*
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* do_clocktick *
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*===========================================================================*/
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PRIVATE int do_clocktick(m_ptr)
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message *m_ptr; /* pointer to request message */
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{
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/* Despite its name, this routine is not called on every clock tick. It
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* is called on those clock ticks when a lot of work needs to be done.
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*/
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/* Check if a clock timer expired and run its watchdog function. */
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if (next_timeout <= realtime) {
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tmrs_exptimers(&clock_timers, realtime, NULL);
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next_timeout = clock_timers == NULL ?
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TMR_NEVER : clock_timers->tmr_exp_time;
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}
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/* A process used up a full quantum. The interrupt handler stored this
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* process in 'prev_ptr'. Reset the quantum and schedule another process.
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*/
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if (prev_ptr->p_sched_ticks <= 0) {
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lock_sched(prev_ptr);
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}
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/* Inhibit sending a reply. */
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return(EDONTREPLY);
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}
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/*===========================================================================*
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* clock_handler *
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*===========================================================================*/
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PRIVATE int clock_handler(hook)
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irq_hook_t *hook;
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{
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/* This executes on each clock tick (i.e., every time the timer chip generates
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* an interrupt). It does a little bit of work so the clock task does not have
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* to be called on every tick. The clock task is called when:
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*
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* (1) the scheduling quantum of the running process has expired, or
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* (2) a timer has expired and the watchdog function should be run.
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*
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* Many global global and static variables are accessed here. The safety of
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* this must be justified. All scheduling and message passing code acquires a
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* lock by temporarily disabling interrupts, so no conflicts with calls from
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* the task level can occur. Furthermore, interrupts are not reentrant, the
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* interrupt handler cannot be bothered by other interrupts.
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*
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* Variables that are updated in the clock's interrupt handler:
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* lost_ticks:
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* Clock ticks counted outside the clock task. This for example
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* is used when the boot monitor processes a real mode interrupt.
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* realtime:
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* The current uptime is incremented with all outstanding ticks.
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* proc_ptr, bill_ptr:
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* These are used for accounting. It does not matter if proc.c
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* is changing them, provided they are always valid pointers,
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* since at worst the previous process would be billed.
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*/
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register unsigned ticks;
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/* Acknowledge the PS/2 clock interrupt. */
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if (machine.ps_mca) outb(PORT_B, inb(PORT_B) | CLOCK_ACK_BIT);
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/* Get number of ticks and update realtime. */
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ticks = lost_ticks + 1;
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lost_ticks = 0;
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realtime += ticks;
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/* Update user and system accounting times. Charge the current process for
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* user time. If the current process is not billable, that is, if a non-user
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* process is running, charge the billable process for system time as well.
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* Thus the unbillable process' user time is the billable user's system time.
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*/
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proc_ptr->p_user_time += ticks;
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if (proc_ptr != bill_ptr) bill_ptr->p_sys_time += ticks;
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if (priv(proc_ptr)->s_flags & PREEMPTIBLE) proc_ptr->p_sched_ticks -= ticks;
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/* Check if do_clocktick() must be called. Done for alarms and scheduling.
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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_sched_ticks <= 0)) {
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prev_ptr = proc_ptr; /* store running process */
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lock_alert(HARDWARE, CLOCK); /* send notification */
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}
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return(1); /* reenable interrupts */
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}
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/*===========================================================================*
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* get_uptime *
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*===========================================================================*/
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PUBLIC clock_t get_uptime()
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{
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/* Get and return the current clock uptime in ticks. */
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return(realtime);
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}
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/*===========================================================================*
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* set_timer *
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*===========================================================================*/
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PUBLIC void set_timer(tp, exp_time, watchdog)
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struct timer *tp; /* pointer to timer structure */
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clock_t exp_time; /* expiration realtime */
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tmr_func_t watchdog; /* watchdog to be called */
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{
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/* Insert the new timer in the active timers list. Always update the
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* next timeout time by setting it to the front of the active list.
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*/
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tmrs_settimer(&clock_timers, tp, exp_time, watchdog, NULL);
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next_timeout = clock_timers->tmr_exp_time;
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}
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/*===========================================================================*
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* reset_timer *
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*===========================================================================*/
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PUBLIC void reset_timer(tp)
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struct timer *tp; /* pointer to timer structure */
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{
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/* The timer pointed to by 'tp' is no longer needed. Remove it from both the
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* active and expired lists. Always update the next timeout time by setting
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* it to the front of the active list.
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*/
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tmrs_clrtimer(&clock_timers, tp, NULL);
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next_timeout = (clock_timers == NULL) ?
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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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PUBLIC unsigned long read_clock()
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{
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/* Read the counter of channel 0 of the 8253A timer. This counter counts
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* down at a rate of TIMER_FREQ and restarts at TIMER_COUNT-1 when it
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* reaches zero. A hardware interrupt (clock tick) occurs when the counter
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* gets to zero and restarts its cycle.
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*/
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unsigned count;
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outb(TIMER_MODE, LATCH_COUNT);
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count = inb(TIMER0);
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count |= (inb(TIMER0) << 8);
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return count;
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}
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#endif /* (CHIP == INTEL) */
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#if (CHIP == M68000)
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/* Initialize the timer C in the MFP 68901: implement init_clock() here. */
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#endif /* (CHIP == M68000) */
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