c977bd8709
when lock timing is enabled in minix/config.h. Added phys_zero() routine to klib386.s that zeroes a range of memory, and added corresponding system call.
367 lines
14 KiB
C
Executable file
367 lines
14 KiB
C
Executable file
/* The file contais the clock task, which handles all time related functions.
|
|
* Important events that are handled by the CLOCK include alarm timers and
|
|
* (re)scheduling user processes.
|
|
* The CLOCK offers a direct interface to kernel processes. System services
|
|
* can access its services through system calls, such as sys_syncalrm(). The
|
|
* CLOCK task thus is hidden for the outside.
|
|
*
|
|
* Changes:
|
|
* Mar 18, 2004 clock interface moved to SYSTEM task (Jorrit N. Herder)
|
|
* Oct 10, 2004 call vector + return values allowed (Jorrit N. Herder)
|
|
* Sep 30, 2004 source code documentation updated (Jorrit N. Herder)
|
|
* Sep 24, 2004 redesigned timers and alarms (Jorrit N. Herder)
|
|
* Jun 04, 2004 new timeout flag alarm functionality (Jorrit N. Herder)
|
|
*
|
|
* The function do_clocktick() is not triggered from the clock library, but
|
|
* by the clock's interrupt handler when a watchdog timer has expired or
|
|
* another user process must be scheduled.
|
|
*
|
|
* In addition to the main clock_task() entry point, which starts the main
|
|
* loop, there are several other minor entry points:
|
|
* clock_stop: called just before MINIX shutdown
|
|
* get_uptime: get realtime since boot in clock ticks
|
|
* set_timer: set a watchdog timer (*, see note below!)
|
|
* reset_timer: reset a watchdog timer (*)
|
|
* calc_elapsed: do timing measurements: get delta ticks and pulses
|
|
* read_clock: read the counter of channel 0 of the 8253A timer
|
|
*
|
|
* (*) The CLOCK task keeps tracks of watchdog timers for the entire kernel.
|
|
* The watchdog functions of expired timers are executed in do_clocktick().
|
|
* It is crucial that watchdog functions cannot block, or the CLOCK task may
|
|
* be blocked. Do not send() a message when the receiver is not expecting it.
|
|
* The use of notify(), which always returns, is strictly preferred!
|
|
*/
|
|
|
|
#include "kernel.h"
|
|
#include "debug.h"
|
|
#include "proc.h"
|
|
#include <signal.h>
|
|
#include <minix/com.h>
|
|
|
|
/* Function prototype for PRIVATE functions. */
|
|
FORWARD _PROTOTYPE( void init_clock, (void) );
|
|
FORWARD _PROTOTYPE( int clock_handler, (irq_hook_t *hook) );
|
|
FORWARD _PROTOTYPE( int do_clocktick, (message *m_ptr) );
|
|
|
|
|
|
/* Constant definitions. */
|
|
#define SCHED_RATE (MILLISEC*HZ/1000) /* number of ticks per schedule */
|
|
#define MILLISEC 100 /* how often to call the scheduler */
|
|
|
|
/* Clock parameters. */
|
|
#if (CHIP == INTEL)
|
|
#define COUNTER_FREQ (2*TIMER_FREQ) /* counter frequency using square wave */
|
|
#define LATCH_COUNT 0x00 /* cc00xxxx, c = channel, x = any */
|
|
#define SQUARE_WAVE 0x36 /* ccaammmb, a = access, m = mode, b = BCD */
|
|
/* 11x11, 11 = LSB then MSB, x11 = sq wave */
|
|
#define TIMER_COUNT ((unsigned) (TIMER_FREQ/HZ)) /* initial value for counter*/
|
|
#define TIMER_FREQ 1193182L /* clock frequency for timer in PC and AT */
|
|
|
|
#define CLOCK_ACK_BIT 0x80 /* PS/2 clock interrupt acknowledge bit */
|
|
#endif
|
|
|
|
#if (CHIP == M68000)
|
|
#define TIMER_FREQ 2457600L /* timer 3 input clock frequency */
|
|
#endif
|
|
|
|
/* The CLOCK's timers queue. The functions in <timers.h> operate on this.
|
|
* The process structure contains one timer per type of alarm (SIGNALRM,
|
|
* SYNCALRM, and FLAGALRM), which means that a process can have a single
|
|
* outstanding timer for each alarm type.
|
|
* If other kernel parts want to use additional timers, they must declare
|
|
* their own persistent timer structure, which can be passed to the clock
|
|
* via (re)set_timer().
|
|
* When a timer expires its watchdog function is run by the CLOCK task.
|
|
*/
|
|
PRIVATE timer_t *clock_timers; /* queue of CLOCK timers */
|
|
PRIVATE clock_t next_timeout; /* realtime that next timer expires */
|
|
|
|
/* The boot time and the current real time. The real time is incremented by
|
|
* the clock on each clock tick. The boot time is set by a utility program
|
|
* after system startup to prevent troubles reading the CMOS.
|
|
*/
|
|
PRIVATE clock_t realtime; /* real time clock */
|
|
|
|
/* Variables for and changed by the CLOCK's interrupt handler. */
|
|
PRIVATE irq_hook_t clock_hook;
|
|
PRIVATE clock_t pending_ticks; /* ticks seen by low level only */
|
|
PRIVATE int sched_ticks = SCHED_RATE; /* counter: when 0, call scheduler */
|
|
PRIVATE struct proc *prev_ptr; /* last user process run by clock */
|
|
|
|
|
|
/*===========================================================================*
|
|
* clock_task *
|
|
*===========================================================================*/
|
|
PUBLIC void clock_task()
|
|
{
|
|
/* Main program of clock task. It corrects realtime by adding pending ticks
|
|
* seen only by the interrupt service, then it determines which call this is
|
|
* by looking at the message type and dispatches.
|
|
*/
|
|
message m; /* message buffer for both input and output */
|
|
int result;
|
|
init_clock(); /* initialize clock task */
|
|
|
|
/* Main loop of the clock task. Get work, process it, sometimes reply. */
|
|
while (TRUE) {
|
|
/* Go get a message. */
|
|
receive(ANY, &m);
|
|
|
|
/* Transfer ticks seen by the low level handler. */
|
|
lock(8, "realtime");
|
|
realtime += pending_ticks;
|
|
pending_ticks = 0;
|
|
unlock(8);
|
|
|
|
/* Handle the request. */
|
|
switch (m.m_type) {
|
|
case HARD_INT:
|
|
result = do_clocktick(&m); /* handle clock tick */
|
|
break;
|
|
default: /* illegal message type */
|
|
kprintf("Warning, illegal CLOCK request from %d.\n", m.m_source);
|
|
result = EBADREQUEST;
|
|
}
|
|
|
|
/* Send reply, unless inhibited, e.g. by do_clocktick(). Use the kernel
|
|
* function lock_send() to prevent a system call trap. The destination
|
|
* is known to be blocked waiting for a message.
|
|
*/
|
|
if (result != EDONTREPLY) {
|
|
m.m_type = result;
|
|
if (OK != lock_send(m.m_source, &m))
|
|
kprintf("Warning, CLOCK couldn't reply to %d.\n", m.m_source);
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
/*===========================================================================*
|
|
* do_clocktick *
|
|
*===========================================================================*/
|
|
PRIVATE int do_clocktick(m_ptr)
|
|
message *m_ptr; /* pointer to request message */
|
|
{
|
|
/* Despite its name, this routine is not called on every clock tick. It
|
|
* is called on those clock ticks when a lot of work needs to be done.
|
|
*/
|
|
register struct proc *rp;
|
|
register int proc_nr;
|
|
timer_t *tp;
|
|
struct proc *p;
|
|
|
|
/* Check if a clock timer expired and run its watchdog function. */
|
|
if (next_timeout <= realtime) {
|
|
tmrs_exptimers(&clock_timers, realtime);
|
|
next_timeout = clock_timers == NULL ?
|
|
TMR_NEVER : clock_timers->tmr_exp_time;
|
|
}
|
|
|
|
/* If a process has been running too long, pick another one. */
|
|
if (--sched_ticks <= 0) {
|
|
if (bill_ptr == prev_ptr)
|
|
lock_sched(PPRI_USER); /* process has run too long */
|
|
sched_ticks = SCHED_RATE; /* reset quantum */
|
|
prev_ptr = bill_ptr; /* new previous process */
|
|
}
|
|
|
|
/* Inhibit sending a reply. */
|
|
return(EDONTREPLY);
|
|
}
|
|
|
|
|
|
/*===========================================================================*
|
|
* clock_handler *
|
|
*===========================================================================*/
|
|
PRIVATE int clock_handler(hook)
|
|
irq_hook_t *hook;
|
|
{
|
|
/* This executes on every clock tick (i.e., every time the timer chip
|
|
* generates an interrupt). It does a little bit of work so the clock
|
|
* task does not have to be called on every tick.
|
|
*
|
|
* Switch context to do_clocktick() if an alarm has gone off.
|
|
* Also switch there to reschedule if the reschedule will do something.
|
|
* This happens when
|
|
* (1) quantum has expired
|
|
* (2) current process received full quantum (as clock sampled it!)
|
|
* (3) something else is ready to run.
|
|
*
|
|
* Many global global and static variables are accessed here. The safety
|
|
* of this must be justified. Most of them are not changed here:
|
|
* proc_ptr, bill_ptr:
|
|
* These are used for accounting. It does not matter if proc.c
|
|
* is changing them, provided they are always valid pointers,
|
|
* since at worst the previous process would be billed.
|
|
* next_timeout, realtime, sched_ticks, bill_ptr, prev_ptr
|
|
* rdy_head[PPRI_USER]
|
|
* These are tested to decide whether to call notify(). It
|
|
* does not matter if the test is sometimes (rarely) backwards
|
|
* due to a race, since this will only delay the high-level
|
|
* processing by one tick, or call the high level unnecessarily.
|
|
* The variables which are changed require more care:
|
|
* rp->p_user_time, rp->p_sys_time:
|
|
* These are protected by explicit locks in system.c.
|
|
* pending_ticks:
|
|
* This is protected by explicit locks in clock.c. Don't
|
|
* update realtime directly, since there are too many
|
|
* references to it to guard conveniently.
|
|
* lost_ticks:
|
|
* Clock ticks counted outside the clock task.
|
|
* sched_ticks, prev_ptr:
|
|
* Updating these competes with similar code in do_clocktick().
|
|
* No lock is necessary, because if bad things happen here
|
|
* (like sched_ticks going negative), the code in do_clocktick()
|
|
* will restore the variables to reasonable values, and an
|
|
* occasional missed or extra sched() is harmless.
|
|
*
|
|
* Are these complications worth the trouble? Well, they make the system 15%
|
|
* faster on a 5MHz 8088, and make task debugging much easier since there are
|
|
* no task switches on an inactive system.
|
|
*/
|
|
register struct proc *rp;
|
|
register unsigned ticks;
|
|
message m;
|
|
clock_t now;
|
|
|
|
/* Acknowledge the PS/2 clock interrupt. */
|
|
if (machine.ps_mca) outb(PORT_B, inb(PORT_B) | CLOCK_ACK_BIT);
|
|
|
|
/* Update user and system accounting times. Charge the current process for
|
|
* user time. If the current process is not billable, that is, if a non-user
|
|
* process is running, charge the billable process for system time as well.
|
|
* Thus the unbillable process' user time is the billable user's system time.
|
|
*/
|
|
ticks = lost_ticks + 1;
|
|
lost_ticks = 0;
|
|
pending_ticks += ticks;
|
|
now = realtime + pending_ticks;
|
|
|
|
/* Update administration. */
|
|
proc_ptr->p_user_time += ticks;
|
|
if (proc_ptr != bill_ptr) bill_ptr->p_sys_time += ticks;
|
|
|
|
/* Check if do_clocktick() must be called. Done for alarms and scheduling.
|
|
* If bill_ptr == prev_ptr, there are no ready users so don't need sched().
|
|
*/
|
|
if (next_timeout <= now || (sched_ticks == 1 && bill_ptr == prev_ptr
|
|
&& rdy_head[PPRI_USER] != NIL_PROC))
|
|
{
|
|
m.NOTIFY_TYPE = HARD_INT;
|
|
lock_notify(CLOCK, &m);
|
|
}
|
|
else if (--sched_ticks <= 0) {
|
|
sched_ticks = SCHED_RATE; /* reset the quantum */
|
|
prev_ptr = bill_ptr; /* new previous process */
|
|
}
|
|
return(1); /* reenable clock interrupts */
|
|
}
|
|
|
|
|
|
/*===========================================================================*
|
|
* get_uptime *
|
|
*===========================================================================*/
|
|
PUBLIC clock_t get_uptime()
|
|
{
|
|
/* Get and return the current clock uptime in ticks.
|
|
* Be careful about pending_ticks.
|
|
*/
|
|
clock_t uptime;
|
|
|
|
lock(9, "get_uptime");
|
|
uptime = realtime + pending_ticks;
|
|
unlock(9);
|
|
return(uptime);
|
|
}
|
|
|
|
|
|
/*===========================================================================*
|
|
* set_timer *
|
|
*===========================================================================*/
|
|
PUBLIC void set_timer(tp, exp_time, watchdog)
|
|
struct timer *tp; /* pointer to timer structure */
|
|
clock_t exp_time; /* expiration realtime */
|
|
tmr_func_t watchdog; /* watchdog to be called */
|
|
{
|
|
/* Insert the new timer in the active timers list. Always update the
|
|
* next timeout time by setting it to the front of the active list.
|
|
*/
|
|
tmrs_settimer(&clock_timers, tp, exp_time, watchdog);
|
|
next_timeout = clock_timers->tmr_exp_time;
|
|
}
|
|
|
|
|
|
/*===========================================================================*
|
|
* reset_timer *
|
|
*===========================================================================*/
|
|
PUBLIC void reset_timer(tp)
|
|
struct timer *tp; /* pointer to timer structure */
|
|
{
|
|
/* The timer pointed to by 'tp' is no longer needed. Remove it from both the
|
|
* active and expired lists. Always update the next timeout time by setting
|
|
* it to the front of the active list.
|
|
*/
|
|
tmrs_clrtimer(&clock_timers, tp);
|
|
next_timeout = (clock_timers == NULL) ?
|
|
TMR_NEVER : clock_timers->tmr_exp_time;
|
|
}
|
|
|
|
|
|
#if (CHIP == INTEL)
|
|
|
|
/*===========================================================================*
|
|
* init_clock *
|
|
*===========================================================================*/
|
|
PRIVATE void init_clock()
|
|
{
|
|
/* Initialize the CLOCK's interrupt hook. */
|
|
clock_hook.proc_nr = CLOCK;
|
|
|
|
/* Initialize channel 0 of the 8253A timer to, e.g., 60 Hz. */
|
|
outb(TIMER_MODE, SQUARE_WAVE); /* set timer to run continuously */
|
|
outb(TIMER0, TIMER_COUNT); /* load timer low byte */
|
|
outb(TIMER0, TIMER_COUNT >> 8); /* load timer high byte */
|
|
put_irq_handler(&clock_hook, CLOCK_IRQ, clock_handler);/* register handler */
|
|
enable_irq(&clock_hook); /* ready for clock interrupts */
|
|
}
|
|
|
|
/*===========================================================================*
|
|
* clock_stop *
|
|
*===========================================================================*/
|
|
PUBLIC void clock_stop()
|
|
{
|
|
/* Reset the clock to the BIOS rate. (For rebooting) */
|
|
outb(TIMER_MODE, 0x36);
|
|
outb(TIMER0, 0);
|
|
outb(TIMER0, 0);
|
|
}
|
|
|
|
|
|
/*===========================================================================*
|
|
* read_clock *
|
|
*===========================================================================*/
|
|
PUBLIC unsigned long read_clock()
|
|
{
|
|
/* Read the counter of channel 0 of the 8253A timer. This counter counts
|
|
* down at a rate of TIMER_FREQ and restarts at TIMER_COUNT-1 when it
|
|
* reaches zero. A hardware interrupt (clock tick) occurs when the counter
|
|
* gets to zero and restarts its cycle.
|
|
*/
|
|
unsigned count;
|
|
|
|
lock(10, "read_clock");
|
|
outb(TIMER_MODE, LATCH_COUNT);
|
|
count = inb(TIMER0);
|
|
count |= (inb(TIMER0) << 8);
|
|
unlock(10);
|
|
|
|
return count;
|
|
}
|
|
|
|
#endif /* (CHIP == INTEL) */
|
|
|
|
#if (CHIP == M68000)
|
|
/* Initialize the timer C in the MFP 68901: implement init_clock() here. */
|
|
#endif /* (CHIP == M68000) */
|
|
|
|
|