CVS commit: src/sys/kern

[Jaromir Dolecek]

Module Name:    src
Committed By:   jdolecek
Date:           Tue Jan 26 19:09:18 UTC 2021

Modified Files:
        src/sys/kern: kern_event.c

Log Message:
call f_touch with kq_lock held, and without KERNEL_LOCK() - for this
adjust EVFILT_USER, which is the only filter actually using that hook

kqueue_scan() now doesn't need to exit/enter the kq_lock when calling
f_touch, which removes another possible race

part of PR kern/50094


To generate a diff of this commit:
cvs rdiff -u -r1.115 -r1.116 src/sys/kern/kern_event.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.


Modified files:

Index: src/sys/kern/kern_event.c
diff -u src/sys/kern/kern_event.c:1.115 src/sys/kern/kern_event.c:1.116
--- src/sys/kern/kern_event.c:1.115	Mon Jan 25 19:57:05 2021
+++ src/sys/kern/kern_event.c	Tue Jan 26 19:09:18 2021
@@ -1,4 +1,4 @@
-/*	$NetBSD: kern_event.c,v 1.115 2021/01/25 19:57:05 jdolecek Exp $	*/
+/*	$NetBSD: kern_event.c,v 1.116 2021/01/26 19:09:18 jdolecek Exp $	*/
 
 /*-
  * Copyright (c) 2008, 2009 The NetBSD Foundation, Inc.
@@ -59,7 +59,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_event.c,v 1.115 2021/01/25 19:57:05 jdolecek Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_event.c,v 1.116 2021/01/26 19:09:18 jdolecek Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -838,7 +838,8 @@ filt_usertouch(struct knote *kn, struct 
 	struct kqueue *kq = kn->kn_kq;
 	int ffctrl;
 
-	mutex_spin_enter(&kq->kq_lock);
+	KASSERT(mutex_owned(&kq->kq_lock));
+
 	switch (type) {
 	case EVENT_REGISTER:
 		if (kev->fflags & NOTE_TRIGGER)
@@ -889,7 +890,6 @@ filt_usertouch(struct knote *kn, struct 
 		panic("filt_usertouch() - invalid type (%ld)", type);
 		break;
 	}
-	mutex_spin_exit(&kq->kq_lock);
 }
 
 /*
@@ -925,7 +925,6 @@ const struct filterops seltrue_filtops =
 	.f_attach = NULL,
 	.f_detach = filt_seltruedetach,
 	.f_event = filt_seltrue,
-	.f_touch = NULL,
 };
 
 int
@@ -1276,9 +1275,9 @@ kqueue_register(struct kqueue *kq, struc
 	kn->kn_kevent.udata = kev->udata;
 	KASSERT(kn->kn_fop != NULL);
 	if (!kn->kn_fop->f_isfd && kn->kn_fop->f_touch != NULL) {
-		KERNEL_LOCK(1, NULL);			/* XXXSMP */
+		mutex_spin_enter(&kq->kq_lock);
 		(*kn->kn_fop->f_touch)(kn, kev, EVENT_REGISTER);
-		KERNEL_UNLOCK_ONE(NULL);		/* XXXSMP */
+		mutex_spin_exit(&kq->kq_lock);
 	} else {
 		kn->kn_sfflags = kev->fflags;
 		kn->kn_sdata = kev->data;
@@ -1529,11 +1528,7 @@ relock:
 				kn->kn_fop->f_touch != NULL);
 		/* XXXAD should be got from f_event if !oneshot. */
 		if (touch) {
-			mutex_spin_exit(&kq->kq_lock);
-			KERNEL_LOCK(1, NULL);		/* XXXSMP */
 			(*kn->kn_fop->f_touch)(kn, kevp, EVENT_PROCESS);
-			KERNEL_UNLOCK_ONE(NULL);	/* XXXSMP */
-			mutex_spin_enter(&kq->kq_lock);
 		} else {
 			*kevp = kn->kn_kevent;
 		}