[src/trunk]: src/sys/kern Consistently reference kn->kn_data only within the ...

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

details:   https://anonhg.NetBSD.org/src/rev/a63b21f15434
branches:  trunk
changeset: 1023827:a63b21f15434
user:      thorpej <thorpej%NetBSD.org@localhost>
date:      Mon Sep 27 00:40:49 2021 +0000

description:
Consistently reference kn->kn_data only within the lock perimeter in
the filtops f_event() callback.

diffstat:

 sys/kern/sys_eventfd.c |  12 ++++++++----
 sys/kern/sys_timerfd.c |   8 +++++---
 sys/kern/tty.c         |   8 +++++---
 3 files changed, 18 insertions(+), 10 deletions(-)

diffs (141 lines):

diff -r 4752f98e2341 -r a63b21f15434 sys/kern/sys_eventfd.c
--- a/sys/kern/sys_eventfd.c    Sun Sep 26 23:37:40 2021 +0000
+++ b/sys/kern/sys_eventfd.c    Mon Sep 27 00:40:49 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sys_eventfd.c,v 1.6 2021/09/26 03:42:54 thorpej Exp $  */
+/*     $NetBSD: sys_eventfd.c,v 1.7 2021/09/27 00:40:49 thorpej Exp $  */
 
 /*-
  * Copyright (c) 2020 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sys_eventfd.c,v 1.6 2021/09/26 03:42:54 thorpej Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sys_eventfd.c,v 1.7 2021/09/27 00:40:49 thorpej Exp $");
 
 /*
  * eventfd
@@ -408,6 +408,7 @@
 eventfd_filt_read(struct knote * const kn, long const hint)
 {
        struct eventfd * const efd = ((file_t *)kn->kn_obj)->f_eventfd;
+       int rv;
 
        if (hint & NOTE_SUBMIT) {
                KASSERT(mutex_owned(&efd->efd_lock));
@@ -416,12 +417,13 @@
        }
 
        kn->kn_data = (int64_t)efd->efd_val;
+       rv = (eventfd_t)kn->kn_data > 0;
 
        if ((hint & NOTE_SUBMIT) == 0) {
                mutex_exit(&efd->efd_lock);
        }
 
-       return (eventfd_t)kn->kn_data > 0;
+       return rv;
 }
 
 static const struct filterops eventfd_read_filterops = {
@@ -445,6 +447,7 @@
 eventfd_filt_write(struct knote * const kn, long const hint)
 {
        struct eventfd * const efd = ((file_t *)kn->kn_obj)->f_eventfd;
+       int rv;
 
        if (hint & NOTE_SUBMIT) {
                KASSERT(mutex_owned(&efd->efd_lock));
@@ -453,12 +456,13 @@
        }
 
        kn->kn_data = (int64_t)efd->efd_val;
+       rv = (eventfd_t)kn->kn_data < EVENTFD_MAXVAL;
 
        if ((hint & NOTE_SUBMIT) == 0) {
                mutex_exit(&efd->efd_lock);
        }
 
-       return (eventfd_t)kn->kn_data < EVENTFD_MAXVAL;
+       return rv;
 }
 
 static const struct filterops eventfd_write_filterops = {
diff -r 4752f98e2341 -r a63b21f15434 sys/kern/sys_timerfd.c
--- a/sys/kern/sys_timerfd.c    Sun Sep 26 23:37:40 2021 +0000
+++ b/sys/kern/sys_timerfd.c    Mon Sep 27 00:40:49 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sys_timerfd.c,v 1.5 2021/09/26 03:42:54 thorpej Exp $  */
+/*     $NetBSD: sys_timerfd.c,v 1.6 2021/09/27 00:40:49 thorpej Exp $  */
 
 /*-
  * Copyright (c) 2020 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sys_timerfd.c,v 1.5 2021/09/26 03:42:54 thorpej Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sys_timerfd.c,v 1.6 2021/09/27 00:40:49 thorpej Exp $");
 
 /*
  * timerfd
@@ -404,6 +404,7 @@
 timerfd_filt_read(struct knote * const kn, long const hint)
 {
        struct timerfd * const tfd = ((file_t *)kn->kn_obj)->f_timerfd;
+       int rv;
 
        if (hint & NOTE_SUBMIT) {
                KASSERT(itimer_lock_held());
@@ -412,12 +413,13 @@
        }
 
        kn->kn_data = (int64_t)timerfd_fire_count(tfd);
+       rv = kn->kn_data != 0;
 
        if ((hint & NOTE_SUBMIT) == 0) {
                itimer_unlock();
        }
 
-       return kn->kn_data != 0;
+       return rv;
 }
 
 static const struct filterops timerfd_read_filterops = {
diff -r 4752f98e2341 -r a63b21f15434 sys/kern/tty.c
--- a/sys/kern/tty.c    Sun Sep 26 23:37:40 2021 +0000
+++ b/sys/kern/tty.c    Mon Sep 27 00:40:49 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: tty.c,v 1.296 2021/09/26 01:16:10 thorpej Exp $        */
+/*     $NetBSD: tty.c,v 1.297 2021/09/27 00:40:49 thorpej Exp $        */
 
 /*-
  * Copyright (c) 2008, 2020 The NetBSD Foundation, Inc.
@@ -63,7 +63,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: tty.c,v 1.296 2021/09/26 01:16:10 thorpej Exp $");
+__KERNEL_RCSID(0, "$NetBSD: tty.c,v 1.297 2021/09/27 00:40:49 thorpej Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_compat_netbsd.h"
@@ -1477,14 +1477,16 @@
 filt_ttyread(struct knote *kn, long hint)
 {
        struct tty      *tp;
+       int rv;
 
        tp = kn->kn_hook;
        if ((hint & NOTE_SUBMIT) == 0)
                mutex_spin_enter(&tty_lock);
        kn->kn_data = ttnread(tp);
+       rv = kn->kn_data > 0;
        if ((hint & NOTE_SUBMIT) == 0)
                mutex_spin_exit(&tty_lock);
-       return (kn->kn_data > 0);
+       return rv;
 }
 
 static void