This adds EVFILT_EXCEPT handler for pipes. It is a subset of
EVFILT_READ; it triggers on EOF only. This captures the POLLHUP
condition of pipe_poll(), used with select(2)'s exceptfds and when
poll(2) has events without (POLLIN | POLLRDNORM | POLLOUT | POLLWRNORM).
OK?
Index: kern/sys_pipe.c
===================================================================
RCS file: src/sys/kern/sys_pipe.c,v
retrieving revision 1.129
diff -u -p -r1.129 sys_pipe.c
--- kern/sys_pipe.c 24 Oct 2021 06:59:54 -0000 1.129
+++ kern/sys_pipe.c 6 Dec 2021 16:04:55 -0000
@@ -85,6 +85,10 @@ int filt_pipewrite(struct knote *kn, lon
int filt_pipewritemodify(struct kevent *kev, struct knote *kn);
int filt_pipewriteprocess(struct knote *kn, struct kevent *kev);
int filt_pipewrite_common(struct knote *kn, struct pipe *rpipe);
+int filt_pipeexcept(struct knote *kn, long hint);
+int filt_pipeexceptmodify(struct kevent *kev, struct knote *kn);
+int filt_pipeexceptprocess(struct knote *kn, struct kevent *kev);
+int filt_pipeexcept_common(struct knote *kn, struct pipe *rpipe);
const struct filterops pipe_rfiltops = {
.f_flags = FILTEROP_ISFD | FILTEROP_MPSAFE,
@@ -104,6 +108,15 @@ const struct filterops pipe_wfiltops = {
.f_process = filt_pipewriteprocess,
};
+const struct filterops pipe_efiltops = {
+ .f_flags = FILTEROP_ISFD | FILTEROP_MPSAFE,
+ .f_attach = NULL,
+ .f_detach = filt_pipedetach,
+ .f_event = filt_pipeexcept,
+ .f_modify = filt_pipeexceptmodify,
+ .f_process = filt_pipeexceptprocess,
+};
+
/*
* Default pipe buffer size(s), this can be kind-of large now because pipe
* space is pageable. The pipe code will try to maintain locality of
@@ -908,6 +921,11 @@ pipe_kqfilter(struct file *fp, struct kn
kn->kn_hook = wpipe;
klist_insert_locked(&wpipe->pipe_sel.si_note, kn);
break;
+ case EVFILT_EXCEPT:
+ kn->kn_fop = &pipe_efiltops;
+ kn->kn_hook = rpipe;
+ klist_insert_locked(&rpipe->pipe_sel.si_note, kn);
+ break;
default:
error = EINVAL;
}
@@ -1047,6 +1065,65 @@ filt_pipewriteprocess(struct knote *kn,
return (active);
}
+int
+filt_pipeexcept_common(struct knote *kn, struct pipe *rpipe)
+{
+ struct pipe *wpipe;
+
+ rw_assert_wrlock(rpipe->pipe_lock);
+
+ wpipe = pipe_peer(rpipe);
+
+ if ((rpipe->pipe_state & PIPE_EOF) || wpipe == NULL) {
+ kn->kn_flags |= EV_EOF;
+ if (kn->kn_flags & __EV_POLL)
+ kn->kn_flags |= __EV_HUP;
+ return (1);
+ }
+
+ return (0);
+}
+
+int
+filt_pipeexcept(struct knote *kn, long hint)
+{
+ struct pipe *rpipe = kn->kn_fp->f_data;
+
+ return (filt_pipeexcept_common(kn, rpipe));
+}
+
+int
+filt_pipeexceptmodify(struct kevent *kev, struct knote *kn)
+{
+ struct pipe *rpipe = kn->kn_fp->f_data;
+ int active;
+
+ rw_enter_write(rpipe->pipe_lock);
+ knote_modify(kev, kn);
+ active = filt_pipeexcept_common(kn, rpipe);
+ rw_exit_write(rpipe->pipe_lock);
+
+ return (active);
+}
+
+int
+filt_pipeexceptprocess(struct knote *kn, struct kevent *kev)
+{
+ struct pipe *rpipe = kn->kn_fp->f_data;
+ int active;
+
+ rw_enter_write(rpipe->pipe_lock);
+ if (kev != NULL && (kn->kn_flags & EV_ONESHOT))
+ active = 1;
+ else
+ active = filt_pipeexcept_common(kn, rpipe);
+ if (active)
+ knote_submit(kn, kev);
+ rw_exit_write(rpipe->pipe_lock);
+
+ return (active);
+}
+
void
pipe_init(void)
{
