minix/servers/pm/alarm.c

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/* This file deals with the alarm clock related system calls, eventually
* passing off the work to the functions in timers.c and check_sig() in
* signal.c to pass an alarm signal to a process.
*
* The entry points into this file are:
* do_itimer: perform the ITIMER system call
* do_alarm: perform the ALARM system call
* set_alarm: tell the timer interface to start or stop a process timer
* check_vtimer: check if one of the virtual timers needs to be restarted
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*/
#include "pm.h"
#include <signal.h>
#include <sys/time.h>
#include <string.h>
#include <minix/com.h>
#include "mproc.h"
#include "param.h"
#define US 1000000 /* shortcut for microseconds per second */
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static clock_t ticks_from_timeval(struct timeval *tv);
static void timeval_from_ticks(struct timeval *tv, clock_t ticks);
static int is_sane_timeval(struct timeval *tv);
static void getset_vtimer(struct mproc *mp, int nwhich, struct
itimerval *value, struct itimerval *ovalue);
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static void get_realtimer(struct mproc *mp, struct itimerval *value);
static void set_realtimer(struct mproc *mp, struct itimerval *value);
static void cause_sigalrm(struct timer *tp);
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/*===========================================================================*
* ticks_from_timeval *
*===========================================================================*/
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static clock_t ticks_from_timeval(tv)
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struct timeval *tv;
{
clock_t ticks;
/* Large delays cause a lot of problems. First, the alarm system call
* takes an unsigned seconds count and the library has cast it to an int.
* That probably works, but on return the library will convert "negative"
* unsigneds to errors. Presumably no one checks for these errors, so
* force this call through. Second, If unsigned and long have the same
* size, converting from seconds to ticks can easily overflow. Finally,
* the kernel has similar overflow bugs adding ticks.
*
* Fixing this requires a lot of ugly casts to fit the wrong interface
* types and to avoid overflow traps. ALRM_EXP_TIME has the right type
* (clock_t) although it is declared as long. How can variables like
* this be declared properly without combinatorial explosion of message
* types?
*/
/* In any case, the following conversion must always round up. */
ticks = (clock_t) (system_hz * (unsigned long) tv->tv_sec);
if ( (unsigned long) ticks / system_hz != (unsigned long) tv->tv_sec) {
ticks = LONG_MAX;
} else {
ticks += (clock_t)
((system_hz * (unsigned long) tv->tv_usec + (US-1)) / US);
}
if (ticks < 0) ticks = LONG_MAX;
return(ticks);
}
/*===========================================================================*
* timeval_from_ticks *
*===========================================================================*/
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static void timeval_from_ticks(tv, ticks)
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struct timeval *tv;
clock_t ticks;
{
tv->tv_sec = (long) (ticks / system_hz);
tv->tv_usec = (long) ((ticks % system_hz) * US / system_hz);
}
/*===========================================================================*
* is_sane_timeval *
*===========================================================================*/
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static int is_sane_timeval(tv)
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struct timeval *tv;
{
/* This imposes a reasonable time value range for setitimer. */
return (tv->tv_sec >= 0 && tv->tv_sec <= MAX_SECS &&
tv->tv_usec >= 0 && tv->tv_usec < US);
}
/*===========================================================================*
* do_itimer *
*===========================================================================*/
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int do_itimer()
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{
struct itimerval ovalue, value; /* old and new interval timers */
int setval, getval; /* set and/or retrieve the values? */
int r;
/* Make sure 'which' is one of the defined timers. */
if (m_in.which_timer < 0 || m_in.which_timer >= NR_ITIMERS)
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return(EINVAL);
/* Determine whether to set and/or return the given timer value, based on
* which of the new_val and old_val parameters are nonzero. At least one of
* them must be nonzero.
*/
setval = (m_in.new_val != NULL);
getval = (m_in.old_val != NULL);
if (!setval && !getval) return(EINVAL);
/* If we're setting a new value, copy the new timer from user space.
* Also, make sure its fields have sane values.
*/
if (setval) {
r = sys_datacopy(who_e, (vir_bytes) m_in.new_val,
PM_PROC_NR, (vir_bytes) &value, (phys_bytes) sizeof(value));
if (r != OK) return(r);
if (!is_sane_timeval(&value.it_value) ||
!is_sane_timeval(&value.it_interval))
return(EINVAL);
}
switch (m_in.which_timer) {
case ITIMER_REAL :
if (getval) get_realtimer(mp, &ovalue);
if (setval) set_realtimer(mp, &value);
r = OK;
break;
case ITIMER_VIRTUAL :
case ITIMER_PROF :
getset_vtimer(mp, m_in.which_timer,
(setval) ? &value : NULL,
(getval) ? &ovalue : NULL);
r = OK;
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break;
default:
panic("invalid timer type: %d", m_in.which_timer);
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}
/* If requested, copy the old interval timer to user space. */
if (r == OK && getval) {
r = sys_datacopy(PM_PROC_NR, (vir_bytes) &ovalue,
who_e, (vir_bytes) m_in.old_val, (phys_bytes) sizeof(ovalue));
}
return(r);
}
/*===========================================================================*
* do_alarm *
*===========================================================================*/
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int do_alarm()
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{
struct itimerval value, ovalue;
int remaining; /* previous time left in seconds */
/* retrieve the old timer value, in seconds (rounded up) */
get_realtimer(mp, &ovalue);
remaining = ovalue.it_value.tv_sec;
if (ovalue.it_value.tv_usec > 0) remaining++;
/* set the new timer value */
memset(&value, 0, sizeof(value));
value.it_value.tv_sec = m_in.seconds;
set_realtimer(mp, &value);
/* and return the old timer value */
return(remaining);
}
/*===========================================================================*
* getset_vtimer *
*===========================================================================*/
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static void getset_vtimer(rmp, which, value, ovalue)
struct mproc *rmp;
int which;
struct itimerval *value;
struct itimerval *ovalue;
{
clock_t newticks, *nptr; /* the new timer value, in ticks */
clock_t oldticks, *optr; /* the old ticks value, in ticks */
int r, num;
/* The default is to provide sys_vtimer with two null pointers, i.e. to do
* nothing at all.
*/
optr = nptr = NULL;
/* If the old timer value is to be retrieved, have 'optr' point to the
* location where the old value is to be stored, and copy the interval.
*/
if (ovalue != NULL) {
optr = &oldticks;
timeval_from_ticks(&ovalue->it_interval, rmp->mp_interval[which]);
}
/* If a new timer value is to be set, store the new timer value and have
* 'nptr' point to it. Also, store the new interval.
*/
if (value != NULL) {
newticks = ticks_from_timeval(&value->it_value);
nptr = &newticks;
/* If no timer is set, the interval must be zero. */
if (newticks <= 0)
rmp->mp_interval[which] = 0;
else
rmp->mp_interval[which] =
ticks_from_timeval(&value->it_interval);
}
/* Find out which kernel timer number to use. */
switch (which) {
case ITIMER_VIRTUAL: num = VT_VIRTUAL; break;
case ITIMER_PROF: num = VT_PROF; break;
default: panic("invalid vtimer type: %d", which);
}
/* Make the kernel call. If requested, also retrieve and store
* the old timer value.
*/
if ((r = sys_vtimer(rmp->mp_endpoint, num, nptr, optr)) != OK)
panic("sys_vtimer failed: %d", r);
if (ovalue != NULL) {
/* If the alarm expired already, we should take into account the
* interval. Return zero only if the interval is zero as well.
*/
if (oldticks <= 0) oldticks = rmp->mp_interval[which];
timeval_from_ticks(&ovalue->it_value, oldticks);
}
}
/*===========================================================================*
* check_vtimer *
*===========================================================================*/
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void check_vtimer(proc_nr, sig)
int proc_nr;
int sig;
{
register struct mproc *rmp;
int which, num;
rmp = &mproc[proc_nr];
/* Translate back the given signal to a timer type and kernel number. */
switch (sig) {
case SIGVTALRM: which = ITIMER_VIRTUAL; num = VT_VIRTUAL; break;
case SIGPROF: which = ITIMER_PROF; num = VT_PROF; break;
default: panic("invalid vtimer signal: %d", sig);
}
/* If a repetition interval was set for this virtual timer, tell the
* kernel to set a new timeout for the virtual timer.
*/
if (rmp->mp_interval[which] > 0)
sys_vtimer(rmp->mp_endpoint, num, &rmp->mp_interval[which], NULL);
}
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/*===========================================================================*
* get_realtimer *
*===========================================================================*/
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static void get_realtimer(rmp, value)
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struct mproc *rmp;
struct itimerval *value;
{
clock_t exptime; /* time at which alarm will expire */
clock_t uptime; /* current system time */
clock_t remaining; /* time left on alarm */
int s;
/* First determine remaining time, in ticks, of previous alarm, if set. */
if (rmp->mp_flags & ALARM_ON) {
if ( (s = getticks(&uptime)) != OK)
panic("get_realtimer couldn't get uptime: %d", s);
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exptime = *tmr_exp_time(&rmp->mp_timer);
remaining = exptime - uptime;
/* If the alarm expired already, we should take into account the
* interval. Return zero only if the interval is zero as well.
*/
if (remaining <= 0) remaining = rmp->mp_interval[ITIMER_REAL];
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} else {
remaining = 0;
}
/* Convert the result to a timeval structure. */
timeval_from_ticks(&value->it_value, remaining);
/* Similarly convert and store the interval of the timer. */
timeval_from_ticks(&value->it_interval, rmp->mp_interval[ITIMER_REAL]);
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}
/*===========================================================================*
* set_realtimer *
*===========================================================================*/
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static void set_realtimer(rmp, value)
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struct mproc *rmp;
struct itimerval *value;
{
clock_t ticks; /* New amount of ticks to the next alarm. */
clock_t interval; /* New amount of ticks for the alarm's interval. */
/* Convert the timeval structures in the 'value' structure to ticks. */
ticks = ticks_from_timeval(&value->it_value);
interval = ticks_from_timeval(&value->it_interval);
/* If no timer is set, the interval must be zero. */
if (ticks <= 0) interval = 0;
/* Apply these values. */
set_alarm(rmp, ticks);
rmp->mp_interval[ITIMER_REAL] = interval;
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}
/*===========================================================================*
* set_alarm *
*===========================================================================*/
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void set_alarm(rmp, ticks)
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struct mproc *rmp; /* process that wants the alarm */
clock_t ticks; /* how many ticks delay before the signal */
{
if (ticks > 0) {
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set_timer(&rmp->mp_timer, ticks, cause_sigalrm, rmp->mp_endpoint);
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rmp->mp_flags |= ALARM_ON;
} else if (rmp->mp_flags & ALARM_ON) {
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cancel_timer(&rmp->mp_timer);
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rmp->mp_flags &= ~ALARM_ON;
}
}
/*===========================================================================*
* cause_sigalrm *
*===========================================================================*/
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static void cause_sigalrm(tp)
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struct timer *tp;
{
int proc_nr_n;
register struct mproc *rmp;
/* get process from timer */
if(pm_isokendpt(tmr_arg(tp)->ta_int, &proc_nr_n) != OK) {
printf("PM: ignoring timer for invalid endpoint %d\n",
tmr_arg(tp)->ta_int);
return;
}
rmp = &mproc[proc_nr_n];
if ((rmp->mp_flags & (IN_USE | EXITING)) != IN_USE) return;
if ((rmp->mp_flags & ALARM_ON) == 0) return;
/* If an interval is set, set a new timer; otherwise clear the ALARM_ON flag.
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* The set_alarm call will be calling set_timer from within this callback
* from the expire_timers function. This is safe, but we must not use the
* "tp" structure below this point anymore.
*/
if (rmp->mp_interval[ITIMER_REAL] > 0)
set_alarm(rmp, rmp->mp_interval[ITIMER_REAL]);
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else rmp->mp_flags &= ~ALARM_ON;
check_sig(rmp->mp_pid, SIGALRM, FALSE /* ksig */);
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}