minix/kernel/clock.c
2010-01-26 10:59:01 +00:00

313 lines
9.9 KiB
C

/* This file contains the clock task, which handles time related functions.
* Important events that are handled by the CLOCK include setting and
* monitoring alarm timers and deciding when to (re)schedule processes.
* The CLOCK offers a direct interface to kernel processes. System services
* can access its services through system calls, such as sys_setalarm(). The
* CLOCK task thus is hidden from the outside world.
*
* Changes:
* Aug 18, 2006 removed direct hardware access etc, MinixPPC (Ingmar Alting)
* Oct 08, 2005 reordering and comment editing (A. S. Woodhull)
* Mar 18, 2004 clock interface moved to SYSTEM task (Jorrit N. Herder)
* Sep 30, 2004 source code documentation updated (Jorrit N. Herder)
* Sep 24, 2004 redesigned alarm timers (Jorrit N. Herder)
*
* Clock task is notified by the clock's interrupt handler when a timer
* has expired.
*
* 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 (+)
* reset_timer: reset a watchdog timer (+)
* read_clock: read the counter of channel 0 of the 8253A timer
*
* (+) The CLOCK task keeps tracks of watchdog timers for the entire kernel.
* It is crucial that watchdog functions not block, or the CLOCK task may
* be blocked. Do not send() a message when the receiver is not expecting it.
* Instead, notify(), which always returns, should be used.
*/
#include "kernel.h"
#include "proc.h"
#include <minix/com.h>
#include <minix/endpoint.h>
#include "clock.h"
#ifdef CONFIG_WATCHDOG
#include "watchdog.h"
#endif
/* Function prototype for PRIVATE functions.
*/
FORWARD _PROTOTYPE( void init_clock, (void) );
FORWARD _PROTOTYPE( void load_update, (void));
/* The CLOCK's timers queue. The functions in <timers.h> operate on this.
* Each system process possesses a single synchronous alarm timer. If other
* kernel parts want to use additional timers, they must declare their own
* persistent (static) 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 time is incremented by the interrupt handler on each clock tick.
*/
PRIVATE clock_t realtime = 0; /* real time clock */
/*===========================================================================*
* clock_task *
*===========================================================================*/
PUBLIC void clock_task()
{
/* Main program of clock task. If the call is not HARD_INT it is an error.
*/
message m; /* message buffer for both input and output */
int result; /* result returned by the handler */
init_clock(); /* initialize clock task */
/* Main loop of the clock task. Get work, process it. Never reply. */
while(TRUE) {
/* Go get a message. */
result = receive(ANY, &m);
if(result != OK)
minix_panic("receive() failed", result);
/* Handle the request. Only clock ticks are expected. */
if (is_notify(m.m_type)) {
switch (_ENDPOINT_P(m.m_source)) {
case HARDWARE:
tmrs_exptimers(&clock_timers, realtime, NULL);
next_timeout = (clock_timers == NULL) ?
TMR_NEVER : clock_timers->tmr_exp_time;
break;
default: /* illegal request type */
kprintf("CLOCK: illegal notify %d from %d.\n",
m.m_type, m.m_source);
}
}
else {
/* illegal request type */
kprintf("CLOCK: illegal request %d from %d.\n",
m.m_type, m.m_source);
}
}
}
/*===========================================================================*
* init_clock *
*===========================================================================*/
PRIVATE void init_clock()
{
/* Set a watchdog timer to periodically balance the scheduling queues.
Side-effect sets new timer */
balance_queues(NULL);
}
/*
* The boot processor timer interrupt handler. In addition to non-boot cpus it
* keeps real time and notifies the clock task if need be
*/
PUBLIC int bsp_timer_int_handler(void)
{
unsigned ticks;
IDLE_STOP;
if(minix_panicing)
return 0;
/* Get number of ticks and update realtime. */
ticks = lost_ticks + 1;
lost_ticks = 0;
realtime += ticks;
ap_timer_int_handler();
/* if a timer expired, notify the clock task */
if ((next_timeout <= realtime)) {
mini_notify(proc_addr(HARDWARE), CLOCK); /* send notification */
}
if (do_serial_debug)
do_ser_debug();
return(1); /* reenable interrupts */
}
/*===========================================================================*
* get_uptime *
*===========================================================================*/
PUBLIC clock_t get_uptime(void)
{
/* Get and return the current clock uptime in ticks. */
return(realtime);
}
/*===========================================================================*
* 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, NULL);
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, NULL);
next_timeout = (clock_timers == NULL) ?
TMR_NEVER : clock_timers->tmr_exp_time;
}
/*===========================================================================*
* load_update *
*===========================================================================*/
PRIVATE void load_update(void)
{
u16_t slot;
int enqueued = 0, q;
struct proc *p;
/* Load average data is stored as a list of numbers in a circular
* buffer. Each slot accumulates _LOAD_UNIT_SECS of samples of
* the number of runnable processes. Computations can then
* be made of the load average over variable periods, in the
* user library (see getloadavg(3)).
*/
slot = (realtime / system_hz / _LOAD_UNIT_SECS) % _LOAD_HISTORY;
if(slot != kloadinfo.proc_last_slot) {
kloadinfo.proc_load_history[slot] = 0;
kloadinfo.proc_last_slot = slot;
}
/* Cumulation. How many processes are ready now? */
for(q = 0; q < NR_SCHED_QUEUES; q++)
for(p = rdy_head[q]; p != NIL_PROC; p = p->p_nextready)
enqueued++;
kloadinfo.proc_load_history[slot] += enqueued;
/* Up-to-dateness. */
kloadinfo.last_clock = realtime;
}
/*
* Timer interupt handler. This is the only thing executed on non boot
* processors. It is called by bsp_timer_int_handler() on the boot processor
*/
PUBLIC int ap_timer_int_handler(void)
{
/* 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.
*/
unsigned ticks = 1;
int expired = 0;
struct proc * p, * billp;
IDLE_STOP;
#ifdef CONFIG_WATCHDOG
/*
* we need to know whether local timer ticks are happening or whether
* the kernel is locked up. We don't care about overflows as we only
* need to know that it's still ticking or not
*/
watchdog_local_timer_ticks++;
#endif
/* 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.
*/
/* FIXME prepared for get_cpu_local_var() */
p = proc_ptr;
billp = bill_ptr;
p->p_user_time += ticks;
if (priv(p)->s_flags & PREEMPTIBLE) {
p->p_ticks_left -= ticks;
}
if (! (priv(p)->s_flags & BILLABLE)) {
billp->p_sys_time += ticks;
billp->p_ticks_left -= ticks;
}
/* Decrement virtual timers, if applicable. We decrement both the
* virtual and the profile timer of the current process, and if the
* current process is not billable, the timer of the billed process as
* well. If any of the timers expire, do_clocktick() will send out
* signals.
*/
if ((p->p_misc_flags & MF_VIRT_TIMER) &&
(p->p_virt_left -= ticks) <= 0) expired = 1;
if ((p->p_misc_flags & MF_PROF_TIMER) &&
(p->p_prof_left -= ticks) <= 0) expired = 1;
if (! (priv(p)->s_flags & BILLABLE) &&
(billp->p_misc_flags & MF_PROF_TIMER) &&
(billp->p_prof_left -= ticks) <= 0) expired = 1;
/*
* Check if a process-virtual timer expired. Check current process, but
* also bill_ptr - one process's user time is another's system time, and
* the profile timer decreases for both!
*/
vtimer_check(p);
if (p != billp)
vtimer_check(billp);
/* Update load average. */
load_update();
/* check if the process is still runnable after checking the vtimer */
if (p->p_rts_flags == 0 && p->p_ticks_left <= 0 &&
priv(p)->s_flags & PREEMPTIBLE) {
/* this dequeues the process */
RTS_SET(p, RTS_NO_QUANTUM);
}
return 1;
}
PUBLIC int boot_cpu_init_timer(unsigned freq)
{
if (arch_init_local_timer(freq))
return -1;
if (arch_register_local_timer_handler(
(irq_handler_t) bsp_timer_int_handler))
return -1;
return 0;
}