cfd712b424
Now that clock_t is an unsigned value, we can also allow the system uptime to wrap. Essentially, instead of using (a <= b) to see if time a occurs no later than time b, we use (b - a <= CLOCK_MAX / 2). The latter value does not exist, so instead we add TMRDIFF_MAX for that purpose. We must therefore also avoid using values like 0 and LONG_MAX as special values for absolute times. This patch extends the libtimers interface so that it no longer uses 0 to indicate "no timeout". Similarly, TMR_NEVER is now used as special value only when otherwise a relative time difference would be used. A minix_timer structure is now considered in use when it has a watchdog function set, rather than when the absolute expiry time is not TMR_NEVER. A few new macros in <minix/timers.h> help with timer comparison and obtaining properties from a minix_timer structure. This patch also eliminates the union of timer arguments, instead using the only union element that is only used (the integer). This prevents potential problems with e.g. live update. The watchdog function prototype is changed to pass in the argument value rather than a pointer to the timer structure, since obtaining the argument value was the only current use of the timer structure anyway. The result is a somewhat friendlier timers API. The VFS select code required a few more invasive changes to restrict the timer value to the new maximum, effectively matching the timer code in PM. As a side effect, select(2) has been changed to reject invalid timeout values. That required a change to the test set, which relied on the previous, erroneous behavior. Finally, while we're rewriting significant chunks of the timer code anyway, also covert it to KNF and add a few more explanatory comments. Change-Id: Id43165c3fbb140b32b90be2cca7f68dd646ea72e
79 lines
2.7 KiB
C
79 lines
2.7 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(int proc_nr_e);
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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;
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use_abs_time = m_ptr->m_lsys_krn_sys_setalarm.abs_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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/* Return the ticks left on the previous alarm. */
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uptime = get_monotonic();
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if (!tmr_is_set(tp)) {
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m_ptr->m_lsys_krn_sys_setalarm.time_left = TMR_NEVER;
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} else if (tmr_is_first(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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/*
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* Finally, (re)set the timer depending on the expiration time. Note that
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* an absolute time of zero is as valid as any other absolute value, so only
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* a relative time value of zero resets the timer.
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*/
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if (!use_abs_time && exp_time == 0) {
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reset_kernel_timer(tp);
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} else {
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if (!use_abs_time)
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exp_time += uptime;
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set_kernel_timer(tp, exp_time, cause_alarm, caller->p_endpoint);
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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(int proc_nr_e)
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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 as the timer argument. Notify that
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* process with a notification message from CLOCK.
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*/
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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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