Index: share/man/man4/filemon.4
===================================================================
--- share/man/man4/filemon.4
+++ share/man/man4/filemon.4
@@ -31,7 +31,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd January 28, 2016
+.Dd February 29, 2016
 .Dt FILEMON 4
 .Os
 .Sh NAME
@@ -189,8 +189,3 @@
 Loading
 .Nm
 may reduce system performance for the noted syscalls.
-.Pp
-Only children of the set process are logged.
-Processes can escape being traced by double forking.
-This is not seen as a problem as the intended use is build monitoring, which
-does not make sense to have daemons for.
Index: sys/dev/filemon/filemon.c
===================================================================
--- sys/dev/filemon/filemon.c
+++ sys/dev/filemon/filemon.c
@@ -82,23 +82,26 @@
 MALLOC_DECLARE(M_FILEMON);
 MALLOC_DEFINE(M_FILEMON, "filemon", "File access monitor");
 
+struct filemon_proc {
+	TAILQ_ENTRY(filemon_proc) proc; /* List of procs for this filemon. */
+	struct proc *p;
+};
+
 struct filemon {
-	TAILQ_ENTRY(filemon) link;	/* Link into the in-use list. */
+	TAILQ_HEAD(, filemon_proc) procs; /* Pointer to list of procs. */
 	struct sx	lock;		/* Lock mutex for this filemon. */
 	struct file	*fp;		/* Output file pointer. */
-	struct proc     *p;		/* The process being monitored. */
 	char		fname1[MAXPATHLEN]; /* Temporary filename buffer. */
 	char		fname2[MAXPATHLEN]; /* Temporary filename buffer. */
 	char		msgbufr[1024];	/* Output message buffer. */
 };
 
-static TAILQ_HEAD(, filemon) filemons_inuse = TAILQ_HEAD_INITIALIZER(filemons_inuse);
-static TAILQ_HEAD(, filemon) filemons_free = TAILQ_HEAD_INITIALIZER(filemons_free);
-static struct sx access_lock;
-
 static struct cdev *filemon_dev;
 
-#include "filemon_lock.c"
+static void filemon_free(struct filemon *);
+static void filemon_track_process(struct filemon *, struct proc *);
+static void filemon_untrack_process(struct filemon *, struct proc *);
+
 #include "filemon_wrapper.c"
 
 static void
@@ -118,34 +121,135 @@
 }
 
 static void
-filemon_dtr(void *data)
+filemon_free(struct filemon *filemon)
 {
-	struct filemon *filemon = data;
+	size_t len;
+	struct timeval now;
+
+	if (filemon->fp != NULL) {
+		getmicrotime(&now);
+
+		len = snprintf(filemon->msgbufr,
+		    sizeof(filemon->msgbufr),
+		    "# Stop %ju.%06ju\n# Bye bye\n",
+		    (uintmax_t)now.tv_sec, (uintmax_t)now.tv_usec);
 
-	if (filemon != NULL) {
-		struct file *fp;
+		filemon_output(filemon, filemon->msgbufr, len);
+		fdrop(filemon->fp, curthread);
+	}
+
+	sx_xunlock(&filemon->lock);
+	sx_destroy(&filemon->lock);
+	free(filemon, M_FILEMON);
+}
+
+static void
+filemon_track_process(struct filemon *filemon, struct proc *p)
+{
+	struct filemon_proc *filemon_proc;
 
-		/* Follow same locking order as filemon_pid_check. */
-		filemon_lock_write();
-		sx_xlock(&filemon->lock);
+	sx_assert(&filemon->lock, SA_XLOCKED);
 
-		/* Remove from the in-use list. */
-		TAILQ_REMOVE(&filemons_inuse, filemon, link);
+	filemon_proc = malloc(sizeof(struct filemon_proc), M_FILEMON,
+	    M_WAITOK | M_ZERO);
+	filemon_proc->p = p;
+	TAILQ_INSERT_TAIL(&filemon->procs, filemon_proc, proc);
+}
 
-		fp = filemon->fp;
-		filemon->fp = NULL;
-		filemon->p = NULL;
+static void
+filemon_proc_free(struct filemon *filemon,
+    struct filemon_proc *filemon_proc)
+{
 
-		/* Add to the free list. */
-		TAILQ_INSERT_TAIL(&filemons_free, filemon, link);
+	TAILQ_REMOVE(&filemon->procs, filemon_proc, proc);
+	free(filemon_proc, M_FILEMON);
+}
+
+static void
+filemon_untrack_process(struct filemon *filemon, struct proc *p)
+{
+	struct filemon_proc *filemon_proc;
+
+	sx_assert(&filemon->lock, SA_XLOCKED);
+
+	TAILQ_FOREACH(filemon_proc, &filemon->procs, proc) {
+		if (filemon_proc->p == p) {
+			filemon_proc_free(filemon, filemon_proc);
+			break;
+		}
+	}
+}
+
+static int
+filemon_untrack_all_processes(void)
+{
+	int error;
+	struct filemon *filemon;
+	struct proc *p;
+
+	error = 0;
+	sx_slock(&allproc_lock);
+	FOREACH_PROC_IN_SYSTEM(p) {
+		PROC_LOCK(p);
+		if ((filemon = p->p_filemon) != NULL) {
+			if (sx_try_xlock(&filemon->lock)) {
+				p->p_filemon = NULL;
+				PROC_UNLOCK(p);
+				filemon_untrack_process(filemon, p);
+				sx_xunlock(&filemon->lock);
+			} else {
+				PROC_UNLOCK(p);
+				error = EBUSY;
+			}
+		} else
+			PROC_UNLOCK(p);
+	}
+	sx_sunlock(&allproc_lock);
+
+	return (error);
+}
 
-		/* Give up write access. */
-		sx_xunlock(&filemon->lock);
-		filemon_unlock_write();
+/*
+ * Invalidate the passed filemon in all processes.  Uses the filemon.procs
+ * list for efficiency.
+ */
+static void
+filemon_untrack_processes(struct filemon *filemon)
+{
+	struct filemon_proc *filemon_proc, *filemon_proc_tmp;
+	struct proc *p;
 
-		if (fp != NULL)
-			fdrop(fp, curthread);
+	sx_assert(&filemon->lock, SA_XLOCKED);
+
+	/*
+	 * Processes in this list won't go away while here since
+	 * filemon_event_process_exit() will lock on filemon->lock
+	 * which we hold.
+	 */
+	TAILQ_FOREACH_SAFE(filemon_proc, &filemon->procs, proc,
+	    filemon_proc_tmp) {
+		p = filemon_proc->p;
+		PROC_LOCK(p);
+		p->p_filemon = NULL;
+		PROC_UNLOCK(p);
+		filemon_proc_free(filemon, filemon_proc);
 	}
+
+	return;
+}
+
+/* The devfs file is being closed.  Untrace all processes and cleanup. */
+static void
+filemon_dtr(void *data)
+{
+	struct filemon *filemon = data;
+
+	if (filemon == NULL)
+		return;
+
+	sx_xlock(&filemon->lock);
+	filemon_untrack_processes(filemon);
+	filemon_free(filemon);
 }
 
 static int
@@ -178,11 +282,19 @@
 
 	/* Set the monitored process ID. */
 	case FILEMON_SET_PID:
+		/* Invalidate any existing processes already set. */
+		filemon_untrack_processes(filemon);
+
 		error = pget(*((pid_t *)data), PGET_CANDEBUG | PGET_NOTWEXIT,
 		    &p);
 		if (error == 0) {
-			filemon->p = p;
+			if (p->p_filemon != NULL)
+				error = EBUSY;
+			else
+				p->p_filemon = filemon;
 			PROC_UNLOCK(p);
+			if (error == 0)
+				filemon_track_process(filemon, p);
 		}
 		break;
 
@@ -199,35 +311,19 @@
 filemon_open(struct cdev *dev, int oflags __unused, int devtype __unused,
     struct thread *td __unused)
 {
+	int error;
 	struct filemon *filemon;
 
-	/* Get exclusive write access. */
-	filemon_lock_write();
-
-	if ((filemon = TAILQ_FIRST(&filemons_free)) != NULL)
-		TAILQ_REMOVE(&filemons_free, filemon, link);
-
-	/* Give up write access. */
-	filemon_unlock_write();
-
-	if (filemon == NULL) {
-		filemon = malloc(sizeof(struct filemon), M_FILEMON,
-		    M_WAITOK | M_ZERO);
-		sx_init(&filemon->lock, "filemon");
-	}
+	filemon = malloc(sizeof(struct filemon), M_FILEMON,
+	    M_WAITOK | M_ZERO);
+	sx_init(&filemon->lock, "filemon");
+	TAILQ_INIT(&filemon->procs);
 
-	devfs_set_cdevpriv(filemon, filemon_dtr);
+	error = devfs_set_cdevpriv(filemon, filemon_dtr);
+	if (error != 0)
+		filemon_free(filemon);
 
-	/* Get exclusive write access. */
-	filemon_lock_write();
-
-	/* Add to the in-use list. */
-	TAILQ_INSERT_TAIL(&filemons_inuse, filemon, link);
-
-	/* Give up write access. */
-	filemon_unlock_write();
-
-	return (0);
+	return (error);
 }
 
 static int
@@ -241,7 +337,6 @@
 static void
 filemon_load(void *dummy __unused)
 {
-	sx_init(&access_lock, "filemons_inuse");
 
 	/* Install the syscall wrappers. */
 	filemon_wrapper_install();
@@ -253,38 +348,15 @@
 static int
 filemon_unload(void)
 {
- 	struct filemon *filemon;
-	int error = 0;
-
-	/* Get exclusive write access. */
-	filemon_lock_write();
-
-	if (TAILQ_FIRST(&filemons_inuse) != NULL)
-		error = EBUSY;
-	else {
-		destroy_dev(filemon_dev);
-
-		/* Deinstall the syscall wrappers. */
-		filemon_wrapper_deinstall();
-	}
+	int error;
 
-	/* Give up write access. */
-	filemon_unlock_write();
-
-	if (error == 0) {
-		/* free() filemon structs free list. */
-		filemon_lock_write();
-		while ((filemon = TAILQ_FIRST(&filemons_free)) != NULL) {
-			TAILQ_REMOVE(&filemons_free, filemon, link);
-			sx_destroy(&filemon->lock);
-			free(filemon, M_FILEMON);
-		}
-		filemon_unlock_write();
-
-		sx_destroy(&access_lock);
-	}
+	destroy_dev(filemon_dev);
+	error = filemon_untrack_all_processes();
+	if (error != 0)
+		return (error);
+	filemon_wrapper_deinstall();
 
-	return (error);
+	return (0);
 }
 
 static int
@@ -301,6 +373,10 @@
 		error = filemon_unload();
 		break;
 
+	case MOD_QUIESCE:
+		error = filemon_untrack_all_processes();
+		break;
+
 	case MOD_SHUTDOWN:
 		break;
 
Index: sys/dev/filemon/filemon_lock.c
===================================================================
--- sys/dev/filemon/filemon_lock.c
+++ /dev/null
@@ -1,57 +0,0 @@
-/*-
- * Copyright (c) 2009-2011, Juniper Networks, Inc.
- * Copyright (c) 2015, EMC Corp.
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY JUNIPER NETWORKS AND CONTRIBUTORS ``AS IS'' AND
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED. IN NO EVENT SHALL JUNIPER NETWORKS OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
- * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
- * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- */
-
-#include <sys/cdefs.h>
-__FBSDID("$FreeBSD$");
-
-static __inline void
-filemon_lock_read(void)
-{
-
-	sx_slock(&access_lock);
-}
-
-static __inline void
-filemon_unlock_read(void)
-{
-
-	sx_sunlock(&access_lock);
-}
-
-static __inline void
-filemon_lock_write(void)
-{
-
-	sx_xlock(&access_lock);
-}
-
-static __inline void
-filemon_unlock_write(void)
-{
-
-	sx_xunlock(&access_lock);
-}
Index: sys/dev/filemon/filemon_wrapper.c
===================================================================
--- sys/dev/filemon/filemon_wrapper.c
+++ sys/dev/filemon/filemon_wrapper.c
@@ -69,26 +69,14 @@
 {
 	struct filemon *filemon;
 
-	filemon_lock_read();
-	if (TAILQ_EMPTY(&filemons_inuse)) {
-		filemon_unlock_read();
+	PROC_LOCK(p);
+	filemon = p->p_filemon;
+	PROC_UNLOCK(p);
+
+	if (filemon == NULL)
 		return (NULL);
-	}
-	sx_slock(&proctree_lock);
-	while (p->p_pid != 0) {
-		TAILQ_FOREACH(filemon, &filemons_inuse, link) {
-			if (p == filemon->p) {
-				sx_sunlock(&proctree_lock);
-				sx_xlock(&filemon->lock);
-				filemon_unlock_read();
-				return (filemon);
-			}
-		}
-		p = proc_realparent(p);
-	}
-	sx_sunlock(&proctree_lock);
-	filemon_unlock_read();
-	return (NULL);
+	sx_xlock(&filemon->lock);
+	return (filemon);
 }
 
 static int
@@ -407,10 +395,6 @@
 {
 	size_t len;
 	struct filemon *filemon;
-	struct timeval now;
-
-	/* Get timestamp before locking. */
-	getmicrotime(&now);
 
 	if ((filemon = filemon_pid_check(p)) != NULL) {
 		len = snprintf(filemon->msgbufr, sizeof(filemon->msgbufr),
@@ -418,16 +402,11 @@
 
 		filemon_output(filemon, filemon->msgbufr, len);
 
-		/* Check if the monitored process is about to exit. */
-		if (filemon->p == p) {
-			len = snprintf(filemon->msgbufr,
-			    sizeof(filemon->msgbufr),
-			    "# Stop %ju.%06ju\n# Bye bye\n",
-			    (uintmax_t)now.tv_sec, (uintmax_t)now.tv_usec);
+		PROC_LOCK(p);
+		p->p_filemon = NULL;
+		PROC_UNLOCK(p);
 
-			filemon_output(filemon, filemon->msgbufr, len);
-			filemon->p = NULL;
-		}
+		filemon_untrack_process(filemon, p);
 
 		sx_xunlock(&filemon->lock);
 	}
@@ -473,6 +452,12 @@
 
 		filemon_output(filemon, filemon->msgbufr, len);
 
+		PROC_LOCK(p2);
+		p2->p_filemon = filemon;
+		PROC_UNLOCK(p2);
+
+		filemon_track_process(filemon, p2);
+
 		sx_xunlock(&filemon->lock);
 	}
 }
Index: sys/kern/kern_proc.c
===================================================================
--- sys/kern/kern_proc.c
+++ sys/kern/kern_proc.c
@@ -249,6 +249,7 @@
 	EVENTHANDLER_INVOKE(process_init, p);
 	p->p_stats = pstats_alloc();
 	p->p_pgrp = NULL;
+	p->p_filemon = NULL;
 	SDT_PROBE3(proc, , init, return, p, size, flags);
 	return (0);
 }
Index: sys/sys/proc.h
===================================================================
--- sys/sys/proc.h
+++ sys/sys/proc.h
@@ -166,6 +166,7 @@
 struct kaudit_record;
 struct kdtrace_proc;
 struct kdtrace_thread;
+struct filemon;
 struct mqueue_notifier;
 struct nlminfo;
 struct p_sched;
@@ -630,6 +631,7 @@
 	 */
 	LIST_ENTRY(proc) p_orphan;	/* (e) List of orphan processes. */
 	LIST_HEAD(, proc) p_orphans;	/* (e) Pointer to list of orphans. */
+	struct filemon	*p_filemon;	/* (c) filemon-specific data. */
 };
 
 #define	p_session	p_pgrp->pg_session