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Here's a testcase, compile with gcc -g -O2 pthreads_relwait.c -o
pthreads_relwait.exe -lpthread
The testcase should succeed (return 0), and print into the console that it
waited for one second (or more). But when compiled against winpthreads it
returns early, usually a few milliseconds before the deadline (as measured by
QPC).
Tested on a fairly recent (a few months old) i686 mingw-w64 from MSYS2.
Just in case ML eats the attachment, here's the source code:
==================pthreads_relwait.c=====================
#include <stdio.h>
#include <stdint.h>
#include <time.h>
#include <pthread.h>
#include <Windows.h>
#define USEC_PER_SEC 1000000
int func()
{
LARGE_INTEGER freq;
double usec_per_tick;
LARGE_INTEGER ticks;
if (!QueryPerformanceFrequency (&freq) || freq.QuadPart == 0)
return 1;
usec_per_tick = (double) USEC_PER_SEC / freq.QuadPart;
int64_t start;
LARGE_INTEGER start_ticks;
int64_t until;
pthread_mutex_t mutex;
if (pthread_mutex_init (&mutex, NULL) != 0)
return 2;
pthread_condattr_t attr;
pthread_cond_t cond;
pthread_condattr_init (&attr);
if (pthread_cond_init (&cond, &attr) != 0)
return 3;
pthread_condattr_destroy (&attr);
if (!QueryPerformanceCounter (&ticks))
return 4;
start = (int64_t) (ticks.QuadPart * usec_per_tick);
start_ticks = ticks;
until = start + 1000000 /* now + 1 second */;
pthread_mutex_lock (&mutex);
struct timespec ts;
int status = 0;
do
{
int64_t now;
int64_t relative;
if (!QueryPerformanceCounter (&ticks))
return 5;
now = (int64_t) (ticks.QuadPart * usec_per_tick);
if (until <= now)
break;
relative = until - now;
ts.tv_sec = relative / 1000000;
ts.tv_nsec = (relative % 1000000) * 1000;
status = pthread_cond_timedwait_relative_np (&cond,
&mutex,
&ts);
if (status != ETIMEDOUT && status != 0)
{
printf ("status %d\n", status);
return 6;
}
} while (status == 0);
int64_t after;
LARGE_INTEGER after_ticks;
if (!QueryPerformanceCounter (&ticks))
return 7;
after = (int64_t) (ticks.QuadPart * usec_per_tick);
after_ticks = ticks;
pthread_mutex_unlock (&mutex);
LARGE_INTEGER diff_ticks;
diff_ticks.QuadPart = after_ticks.QuadPart - start_ticks.QuadPart;
printf ("started at\n%lld\n"
", ended at\n%lld\n"
", aimed at\n%lld\n"
", difference is\n%lld\n",
start, after, until, after - until);
printf ("started at\n%lld ticks\n"
", ended at\n%lld ticks\n"
", difference is\n%lld ticks\n"
", with\n%lld ticks per second that is %f seconds)\n",
start_ticks, after_ticks, diff_ticks.QuadPart,
freq.QuadPart,
(double) diff_ticks.QuadPart / (double) freq.QuadPart);
if (after < until)
return 8;
pthread_cond_destroy (&cond);
pthread_mutex_destroy (&mutex);
}
int
main (int argc, char **argv)
{
int status = func ();
if (status != 0)
printf ("Non-zero exit code %d\n", status);
return 0;
}
========================================================
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#include <stdio.h>
#include <stdint.h>
#include <time.h>
#include <pthread.h>
#include <Windows.h>
#define USEC_PER_SEC 1000000
int func()
{
LARGE_INTEGER freq;
double usec_per_tick;
LARGE_INTEGER ticks;
if (!QueryPerformanceFrequency (&freq) || freq.QuadPart == 0)
return 1;
usec_per_tick = (double) USEC_PER_SEC / freq.QuadPart;
int64_t start;
LARGE_INTEGER start_ticks;
int64_t until;
pthread_mutex_t mutex;
if (pthread_mutex_init (&mutex, NULL) != 0)
return 2;
pthread_condattr_t attr;
pthread_cond_t cond;
pthread_condattr_init (&attr);
if (pthread_cond_init (&cond, &attr) != 0)
return 3;
pthread_condattr_destroy (&attr);
if (!QueryPerformanceCounter (&ticks))
return 4;
start = (int64_t) (ticks.QuadPart * usec_per_tick);
start_ticks = ticks;
until = start + 1000000 /* now + 1 second */;
pthread_mutex_lock (&mutex);
struct timespec ts;
int status = 0;
do
{
int64_t now;
int64_t relative;
if (!QueryPerformanceCounter (&ticks))
return 5;
now = (int64_t) (ticks.QuadPart * usec_per_tick);
if (until <= now)
break;
relative = until - now;
ts.tv_sec = relative / 1000000;
ts.tv_nsec = (relative % 1000000) * 1000;
status = pthread_cond_timedwait_relative_np (&cond,
&mutex,
&ts);
if (status != ETIMEDOUT && status != 0)
{
printf ("status %d\n", status);
return 6;
}
} while (status == 0);
int64_t after;
LARGE_INTEGER after_ticks;
if (!QueryPerformanceCounter (&ticks))
return 7;
after = (int64_t) (ticks.QuadPart * usec_per_tick);
after_ticks = ticks;
pthread_mutex_unlock (&mutex);
LARGE_INTEGER diff_ticks;
diff_ticks.QuadPart = after_ticks.QuadPart - start_ticks.QuadPart;
printf ("started at\n%lld\n"
", ended at\n%lld\n"
", aimed at\n%lld\n"
", difference is\n%lld\n",
start, after, until, after - until);
printf ("started at\n%lld ticks\n"
", ended at\n%lld ticks\n"
", difference is\n%lld ticks\n"
", with\n%lld ticks per second that is %f seconds)\n",
start_ticks, after_ticks, diff_ticks.QuadPart,
freq.QuadPart,
(double) diff_ticks.QuadPart / (double) freq.QuadPart);
if (after < until)
return 8;
pthread_cond_destroy (&cond);
pthread_mutex_destroy (&mutex);
}
int
main (int argc, char **argv)
{
int status = func ();
if (status != 0)
printf ("Non-zero exit code %d\n", status);
return 0;
}
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