e10ce184e4
Previously, there was a tiny chance that tickdelay(3) would return early or that it would fail to reinstate a previous alarm. - sys_setalarm(2) now returns TMR_NEVER instead of 0 for the time left if no previous alarm was set; - sys_setalarm(2) now also returns the current time, to allow the caller to determine whether it got an alarm notification for the alarm it set or for a previous alarm that has just gone off; - tickdelay(3) now makes use of these facilities. Change-Id: Id4f8fe19a61ca8574f43131964e6f0317f613f49
77 lines
2.8 KiB
C
77 lines
2.8 KiB
C
/* The kernel call implemented in this file:
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* m_type: SYS_SETALARM
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*
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* The parameters for this kernel call are:
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* m_lsys_krn_sys_setalarm.exp_time (alarm's expiration time)
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* m_lsys_krn_sys_setalarm.abs_time (expiration time is absolute?)
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* m_lsys_krn_sys_setalarm.time_left (return seconds left of previous)
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*/
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#include "kernel/system.h"
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#include <minix/endpoint.h>
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#include <assert.h>
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#if USE_SETALARM
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static void cause_alarm(minix_timer_t *tp);
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/*===========================================================================*
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* do_setalarm *
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*===========================================================================*/
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int do_setalarm(struct proc * caller, message * m_ptr)
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{
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/* A process requests a synchronous alarm, or wants to cancel its alarm. */
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long exp_time; /* expiration time for this alarm */
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int use_abs_time; /* use absolute or relative time */
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minix_timer_t *tp; /* the process' timer structure */
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clock_t uptime; /* placeholder for current uptime */
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/* Extract shared parameters from the request message. */
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exp_time = m_ptr->m_lsys_krn_sys_setalarm.exp_time; /* alarm's expiration time */
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use_abs_time = m_ptr->m_lsys_krn_sys_setalarm.abs_time; /* flag for absolute time */
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if (! (priv(caller)->s_flags & SYS_PROC)) return(EPERM);
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/* Get the timer structure and set the parameters for this alarm. */
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tp = &(priv(caller)->s_alarm_timer);
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tmr_arg(tp)->ta_int = caller->p_endpoint;
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tp->tmr_func = cause_alarm;
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/* Return the ticks left on the previous alarm. */
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uptime = get_monotonic();
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if (tp->tmr_exp_time == TMR_NEVER) {
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m_ptr->m_lsys_krn_sys_setalarm.time_left = TMR_NEVER;
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} else if (uptime < tp->tmr_exp_time) {
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m_ptr->m_lsys_krn_sys_setalarm.time_left = (tp->tmr_exp_time - uptime);
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} else {
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m_ptr->m_lsys_krn_sys_setalarm.time_left = 0;
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}
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/* For the caller's convenience, also return the current time. */
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m_ptr->m_lsys_krn_sys_setalarm.uptime = uptime;
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/* Finally, (re)set the timer depending on the expiration time. */
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if (exp_time == 0) {
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reset_kernel_timer(tp);
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} else {
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tp->tmr_exp_time = (use_abs_time) ? exp_time : exp_time + get_monotonic();
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set_kernel_timer(tp, tp->tmr_exp_time, tp->tmr_func);
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}
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return(OK);
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}
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/*===========================================================================*
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* cause_alarm *
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*===========================================================================*/
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static void cause_alarm(minix_timer_t *tp)
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{
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/* Routine called if a timer goes off and the process requested a synchronous
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* alarm. The process number is stored in timer argument 'ta_int'. Notify that
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* process with a notification message from CLOCK.
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*/
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endpoint_t proc_nr_e = tmr_arg(tp)->ta_int; /* get process number */
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mini_notify(proc_addr(CLOCK), proc_nr_e); /* notify process */
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}
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#endif /* USE_SETALARM */
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