On Tue, Jul 24, 2001 at 09:13:18PM +0200, Ralf S. Engelschall wrote:
> On Mon, Jul 23, 2001, Shawn Wagner wrote:
>
> >
> > With some more debugging, it looks like using hard syscall wrappers is the
> > problem. Turning that off makes everything work for me, at least (Linux
> > 2.2). With them, pth_sched_eventmanager() isn't always detecting fd i/o with
> > a timeout correctly and was exiting early instead of waiting for an event to
> > happen. This is annoying, since one of the threads does gethostbyaddr()'s,
> > which I didn't want possibly blocking the whole server. But at least it's
> > not aborting now.
>
> Hhmm... so you think it is not a semantical bug in the scheduler, but
> instead a side-effect of some syscalls. What happens if you use the soft
> syscall wrappers? Do you have a _SMALL_ test application at hand which I
> can use to deterministically reproduce the problem?
>
I've narrowed it down further. The problem seemed to be happening after
trying to connect to a port that's not listening (An auth/ident lookup, in
this case). I found a bug in my code returning the wrong value when
this happens, so a later select was done on a closed fd. After fixing
that, everything's working good... and I have no idea why this wasn't
happening all the time instead of just with hard syscalls.
The error in my code revealed that the select done in pth_sched_eventmanager()
doesn't deal well with errors besides EINTR (EBADF in my case). The test
program below aborts no matter the syscall setting.
--
Shawn Wagner
[EMAIL PROTECTED]
#include <pth.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
void *thread_select(void *x) {
fd_set r;
struct timeval t;
FD_ZERO(&r);
/* Nice high number that shouldn't be open */
FD_SET(50, &r);
t.tv_sec = 5;
t.tv_usec = 0;
if (pth_select(51, &r, NULL, NULL, &t) < 0)
perror("pth_select");
printf("Never reached.\n");
return NULL;
}
int main(void) {
pth_t child;
pth_attr_t s_attr;
pth_init();
s_attr = pth_attr_new();
pth_attr_set(s_attr, PTH_ATTR_NAME, "select");
child = pth_spawn(s_attr, thread_select, NULL);
pth_join(child, NULL);
return EXIT_SUCCESS;
}
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