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/* ptlinux.c -- portable timer implementation for linux */
/* IMPLEMENTATION NOTES (by Mark Nelson):
Unlike Windows, Linux has no system call to request a periodic callback,
so if Pt_Start() receives a callback parameter, it must create a thread
that wakes up periodically and calls the provided callback function.
If running as superuser, use setpriority() to renice thread to -20.
One could also set the timer thread to a real-time priority (SCHED_FIFO
and SCHED_RR), but this is dangerous for This is necessary because
if the callback hangs it'll never return. A more serious reason
is that the current scheduler implementation busy-waits instead
of sleeping when realtime threads request a sleep of <=2ms (as a way
to get around the 10ms granularity), which means the thread would never
let anyone else on the CPU.
CHANGE LOG
18-Jul-03 Roger Dannenberg -- Simplified code to set priority of timer
thread. Simplified implementation notes.
*/
/* stdlib, stdio, unistd, and sys/types were added because they appeared
* in a Gentoo patch, but I'm not sure why they are needed. -RBD
*/
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include "porttime.h"
#include "sys/time.h"
#include "sys/resource.h"
#include "sys/timeb.h"
#include "pthread.h"
#define TRUE 1
#define FALSE 0
static int time_started_flag = FALSE;
static struct timeb time_offset = {0, 0, 0, 0};
static pthread_t pt_thread_pid;
/* note that this is static data -- we only need one copy */
typedef struct {
int id;
int resolution;
PtCallback *callback;
void *userData;
} pt_callback_parameters;
static int pt_callback_proc_id = 0;
static void *Pt_CallbackProc(void *p)
{
pt_callback_parameters *parameters = (pt_callback_parameters *) p;
int mytime = 1;
/* to kill a process, just increment the pt_callback_proc_id */
/* printf("pt_callback_proc_id %d, id %d\n", pt_callback_proc_id,
parameters->id); */
if (geteuid() == 0) setpriority(PRIO_PROCESS, 0, -20);
while (pt_callback_proc_id == parameters->id) {
/* wait for a multiple of resolution ms */
struct timeval timeout;
int delay = mytime++ * parameters->resolution - Pt_Time();
if (delay < 0) delay = 0;
timeout.tv_sec = 0;
timeout.tv_usec = delay * 1000;
select(0, NULL, NULL, NULL, &timeout);
(*(parameters->callback))(Pt_Time(), parameters->userData);
}
/* printf("Pt_CallbackProc exiting\n"); */
// free(parameters);
return NULL;
}
PtError Pt_Start(int resolution, PtCallback *callback, void *userData)
{
if (time_started_flag) return ptNoError;
ftime(&time_offset); /* need this set before process runs */
if (callback) {
int res;
pt_callback_parameters *parms = (pt_callback_parameters *)
malloc(sizeof(pt_callback_parameters));
if (!parms) return ptInsufficientMemory;
parms->id = pt_callback_proc_id;
parms->resolution = resolution;
parms->callback = callback;
parms->userData = userData;
res = pthread_create(&pt_thread_pid, NULL,
Pt_CallbackProc, parms);
if (res != 0) return ptHostError;
}
time_started_flag = TRUE;
return ptNoError;
}
PtError Pt_Stop()
{
/* printf("Pt_Stop called\n"); */
pt_callback_proc_id++;
pthread_join(pt_thread_pid, NULL);
time_started_flag = FALSE;
return ptNoError;
}
int Pt_Started()
{
return time_started_flag;
}
PtTimestamp Pt_Time()
{
long seconds, milliseconds;
struct timeb now;
ftime(&now);
seconds = now.time - time_offset.time;
milliseconds = now.millitm - time_offset.millitm;
return seconds * 1000 + milliseconds;
}
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