On 29/10/21(Fri) 10:50, Anton Lindqvist wrote:
> On Fri, Oct 29, 2021 at 09:13:58AM +0100, Larry Hynes wrote:
> > Hi
> >
> > In last two snapshots I installed, poll seems to hang in certain
> > circumstances.
> >
> > Here's a reproducer, from Leah Neukirchen (cc'ed on this mail):
Thanks, do you agree to license it under ISC, as in
/usr/share/misc/license.template, so we can put it in src/regress?
> >
> > ------
> >
> > #include <stdio.h>
> > #include <poll.h>
> > #include <unistd.h>
> >
> > int
> > main()
> > {
> > struct pollfd fds[1];
> >
> > fds[0].fd = 0;
> > fds[0].events = POLLIN | POLLHUP;
> > close(0);
> >
> > printf("%d\n", poll(fds, 1, -1));
> > printf("%d\n", fds[0].revents & POLLNVAL);
> > }
> >
> > ------
> >
> > When compiled and run, that should hang on latest snap. It would be
> > expected to return immediately with POLLNVAL set.
>
> I think poll() needs similar handling as select() recently gained.
> Caution, only compile tested.
Here's a simpler fix, do not sleep at all if we already have something
to report.
This works for me, ok?
Index: kern/sys_generic.c
===================================================================
RCS file: /cvs/src/sys/kern/sys_generic.c,v
retrieving revision 1.138
diff -u -p -r1.138 sys_generic.c
--- kern/sys_generic.c 24 Oct 2021 11:23:22 -0000 1.138
+++ kern/sys_generic.c 29 Oct 2021 12:26:48 -0000
@@ -1155,6 +1155,8 @@ doppoll(struct proc *p, struct pollfd *f
/* Register kqueue events */
*retval = ppollregister(p, pl, nfds, &nevents);
+ if (*retval != 0)
+ goto done;
/*
* The poll/select family of syscalls has been designed to
