Date: Fri, 28 Dec 2018 02:14:28 +0100 From: Willem Jan Withagen <wjw@digiware.nl> To: FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Using kqueue with aio_read/write Message-ID: <8753521a-4555-ec2a-5efc-dee2660b4d9b@digiware.nl>
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Hi,
Im trying to understand why I cannot get so code to work.
This is the smallest extract I can make to show my problem.
I would expect the kevent() call to return every timeo tick.
Even if I tell it NOT to time-out I get these spurts of errors
Since there is nothing to trigger the AIO-event, I would expect kqueue
to hold indefinitly.
But it does not generate anything other than errors
And instead it repeatedly complains that there is a permission error:
get_events_kevent: EV_Error(1) kevent(): Operation not permitted
But I'm not getting where that would the case...
Surely a pilot error, but I do overlook it al the time.
So suggestions are welcome.
Thanx,
--WjW
#include <aio.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/event.h>
#include <unistd.h>
#define BUFFER_SIZE 512
#define MAX_EVENTS 32
#define FILENAME "/tmp/aio_test"
char filename[256];
int fd;
int done = 0;
void get_events_kevent(int fd, int kq)
{
printf("get_events function fd = %d, kq = %d\n", fd, kq);
int i = 0, errcnt = 0, err, ret, reterr, rev;
int search = 1;
int timeout_ms = 10;
struct timespec timeo = {
timeout_ms / 1000,
(timeout_ms % 1000) * 1000 * 1000
};
struct kevent filter[16];
struct kevent changed[16];
EV_SET(&filter[0], fd, EVFILT_AIO,
EV_ADD,
0, 0, 0 );
while (!done) {
printf("+");
rev = kevent(kq, filter, 1, changed, 16, 0); //&timeo);
if (rev < 0) {
perror("kevent error");
} else if (rev == 0) {
printf("T");
} else {
printf("rev(%d)\n", rev);
if (changed[0].flags == EV_ERROR) {
errno = changed[0].data;
printf( "%s: EV_Error(%d) kevent(): %s\n", __func__, errno,
strerror(errno));
memset(&changed[0], 0, sizeof(struct kevent));
} else {
err = aio_error((struct aiocb*)changed[0].udata);
ret = aio_return((struct aiocb*)changed[0].udata);
if (ret < 0 )
reterr = errno;
if (err != 0) {
printf( "%s: slot: %d, Error(%d) at aio_error():
%s\n", __func__, i, err, strerror (err));
errcnt++;
if (errcnt > 50) {
exit(3);
}
}
}
}
}
}
int main()
{
(void) strcpy(filename, FILENAME);
unlink(filename);
fd = open(filename, O_CREAT | O_RDWR, S_IRUSR | S_IWUSR);
if (fd == -1) {
printf( "%s: Error at open(): %s\n", __func__, strerror(errno));
exit(1);
}
int kq = kqueue();
if (fd == -1) {
printf( "%s: Error at kqueue(): %s\n", __func__, strerror(errno));
exit(1);
}
get_events_kevent( fd, kq);
close(kq);
close(fd);
return 0;
}
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