Hello, I would like to propose chaging behaviour of pthread_cond_wait().
POSIX states as follows about pthread_cond_wait(): If a signal is delivered to a thread waiting for a condition variable, upon return from the signal handler the thread resumes waiting for the condition variable as if it was not interrupted, or it returns zero due to spurious wakeup. cygwin 2.7.0 employs the latter behaviour, while Debian GNU/Linux and FreeBSD employ the former one. Of course, this is not a cygwin bug. However, IMHO, it is better to have the compatibility with the other major platforms. Because of this difference, iperf 2.0.5 is not terminated normally in cygwin 2.7.0. In client mode, iperf 2.0.5 does not stop after measurement automatically. It needs ^C to stop it. In server mode, iperf 2.0.5 can not stop even by ^C. Simple test case, attached (pt.c), reproduces this problem. I know this test case (and iperf 2.0.5) is essentially unsafe because pthread functions are called from signal handler. But, anyway it works in Debian GNU/Linux and FreeBSD. The test case acts as follows in Debian GNU/Linux and FreeBSD. % gcc pt.c -lpthread; ./a.out Thread 1 Alarm 2 Thread 3 % However, in cygwin, it acs as: % gcc pt.c; ./a.exe Thread 1 (Deadlock: ^C is needed to terminate.) % I would like to propose a patch attached (pthread.patch), for the above reason. With this patch, iperf 2.0.5 as well as the test case works fine. -- Takashi Yano <takashi.y...@nifty.ne.jp>
#include <stdio.h>
#include <unistd.h>
#include <pthread.h>
#include <signal.h>
pthread_mutex_t m = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t c;
int flag = 0;
#define N 2
void sig_handler(int sig)
{
pthread_mutex_lock(&m);
flag ++;
pthread_cond_signal(&c);
printf("Alarm %d\n", flag); fflush(stdout);
pthread_mutex_unlock(&m);
}
void *thread_main(void *args)
{
int i;
for (i=0; i<N; i++) {
pthread_mutex_lock(&m);
flag ++;
pthread_cond_signal(&c);
printf("Thread %d\n", flag); fflush(stdout);
pthread_mutex_unlock(&m);
usleep(2000000);
}
return NULL;
}
int main()
{
pthread_t t;
signal(SIGALRM, sig_handler);
pthread_cond_init(&c, NULL);
pthread_create(&t, NULL, thread_main, NULL);
alarm(1);
pthread_mutex_lock(&m);
while (flag < N+1) {
pthread_cond_wait(&c, &m);
}
pthread_mutex_unlock(&m);
return 0;
}
pthread.patch
Description: Binary data
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