[src/trunk]: src/sys/kern Allow attaching for write, but return no events.

[christos <christos%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/3ac6eeb1ad5f
branches:  trunk
changeset: 357887:3ac6eeb1ad5f
user:      christos <christos%NetBSD.org@localhost>
date:      Fri Dec 01 19:05:49 2017 +0000

description:
Allow attaching for write, but return no events.

diffstat:

 sys/kern/subr_cprng.c |  91 +++++++++++++++++++++++++++++++++-----------------
 1 files changed, 59 insertions(+), 32 deletions(-)

diffs (126 lines):

diff -r 141c205ca29b -r 3ac6eeb1ad5f sys/kern/subr_cprng.c
--- a/sys/kern/subr_cprng.c     Fri Dec 01 19:04:19 2017 +0000
+++ b/sys/kern/subr_cprng.c     Fri Dec 01 19:05:49 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: subr_cprng.c,v 1.28 2017/10/25 08:12:39 maya Exp $ */
+/*     $NetBSD: subr_cprng.c,v 1.29 2017/12/01 19:05:49 christos Exp $ */
 
 /*-
  * Copyright (c) 2011-2013 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: subr_cprng.c,v 1.28 2017/10/25 08:12:39 maya Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_cprng.c,v 1.29 2017/12/01 19:05:49 christos Exp $");
 
 #include <sys/param.h>
 #include <sys/types.h>
@@ -253,35 +253,6 @@
        return result;
 }
 
-static void    filt_cprng_detach(struct knote *);
-static int     filt_cprng_event(struct knote *, long);
-
-static const struct filterops cprng_filtops = {
-       .f_isfd = 1,
-       .f_attach = NULL,
-       .f_detach = filt_cprng_detach,
-       .f_event = filt_cprng_event,
-};
-
-int
-cprng_strong_kqfilter(struct cprng_strong *cprng, struct knote *kn)
-{
-
-       switch (kn->kn_filter) {
-       case EVFILT_READ:
-               kn->kn_fop = &cprng_filtops;
-               kn->kn_hook = cprng;
-               mutex_enter(&cprng->cs_lock);
-               SLIST_INSERT_HEAD(&cprng->cs_selq.sel_klist, kn, kn_selnext);
-               mutex_exit(&cprng->cs_lock);
-               return 0;
-
-       case EVFILT_WRITE:
-       default:
-               return EINVAL;
-       }
-}
-
 static void
 filt_cprng_detach(struct knote *kn)
 {
@@ -293,7 +264,7 @@
 }
 
 static int
-filt_cprng_event(struct knote *kn, long hint)
+filt_cprng_read_event(struct knote *kn, long hint)
 {
        struct cprng_strong *const cprng = kn->kn_hook;
        int ret;
@@ -316,6 +287,62 @@
        return ret;
 }
 
+static int
+filt_cprng_write_event(struct knote *kn, long hint)
+{
+       struct cprng_strong *const cprng = kn->kn_hook;
+
+       if (hint == NOTE_SUBMIT)
+               KASSERT(mutex_owned(&cprng->cs_lock));
+       else
+               mutex_enter(&cprng->cs_lock);
+
+       kn->kn_data = 0;
+
+       if (hint == NOTE_SUBMIT)
+               KASSERT(mutex_owned(&cprng->cs_lock));
+       else
+               mutex_exit(&cprng->cs_lock);
+
+       return 0;
+}
+
+static const struct filterops cprng_read_filtops = {
+       .f_isfd = 1,
+       .f_attach = NULL,
+       .f_detach = filt_cprng_detach,
+       .f_event = filt_cprng_read_event,
+};
+
+static const struct filterops cprng_write_filtops = {
+       .f_isfd = 1,
+       .f_attach = NULL,
+       .f_detach = filt_cprng_detach,
+       .f_event = filt_cprng_write_event,
+};
+
+int
+cprng_strong_kqfilter(struct cprng_strong *cprng, struct knote *kn)
+{
+
+       switch (kn->kn_filter) {
+       case EVFILT_READ:
+               kn->kn_fop = &cprng_read_filtops;
+               break;
+       case EVFILT_WRITE:
+               kn->kn_fop = &cprng_write_filtops;
+               break;
+       default:
+               return EINVAL;
+       }
+
+       kn->kn_hook = cprng;
+       mutex_enter(&cprng->cs_lock);
+       SLIST_INSERT_HEAD(&cprng->cs_selq.sel_klist, kn, kn_selnext);
+       mutex_exit(&cprng->cs_lock);
+       return 0;
+}
+
 int
 cprng_strong_poll(struct cprng_strong *cprng, int events)
 {