diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c
index 88b26af..7407c2c 100644
--- a/sys/kern/kern_descrip.c
+++ b/sys/kern/kern_descrip.c
@@ -131,6 +131,72 @@ static int	fill_socket_info(struct socket *so, struct kinfo_file *kif);
 static int	fill_vnode_info(struct vnode *vp, struct kinfo_file *kif);
 static int	getmaxfd(struct proc *p);
 
+
+#include <machine/cpu.h>
+
+static inline bool
+seq_in_modify(seq_t seqp)
+{
+
+	return (seqp & 1);
+}
+
+static inline void
+seq_write_begin(seq_t *seqp)
+{
+
+	MPASS(!seq_in_modify(*seqp));
+	(*seqp)++;
+	wmb();
+}
+
+static inline void
+seq_write_end(seq_t *seqp)
+{
+
+	wmb();
+	(*seqp)++;
+	MPASS(!seq_in_modify(*seqp));
+}
+
+static __inline seq_t
+seq_read(seq_t *seqp)
+{
+	seq_t ret;
+
+	for (;;) {
+		rmb();
+		ret = *seqp;
+		if (seq_in_modify(ret)) {
+			cpu_spinwait();
+			continue;
+		}
+		break;
+	}
+	rmb();
+
+	return (ret);
+}
+
+
+static inline seq_t
+seq_consistent_nomb(seq_t *seqp, seq_t oldseqp)
+{
+
+	MPASS(!seq_in_modify(oldseqp));
+	return (*seqp == oldseqp);
+}
+
+static inline seq_t
+seq_consistent(seq_t *seqp, seq_t oldseqp)
+{
+
+	rmb();
+	return (seq_consistent_nomb(seqp, oldseqp));
+}
+
+#define fd_seq(fdp, fd)	(&(fdp)->fd_ofiles[(fd)].fde_seq)
+
 /*
  * Each process has:
  *
@@ -301,9 +367,11 @@ fdfree(struct filedesc *fdp, int fd)
 	struct filedescent *fde;
 
 	fde = &fdp->fd_ofiles[fd];
+	seq_write_begin(&fde->fde_seq);
 	filecaps_free(&fde->fde_caps);
-	bzero(fde, sizeof(*fde));
+	bzero(fde_change(fde), fde_change_size);
 	fdunused(fdp, fd);
+	seq_write_end(&fde->fde_seq);
 }
 
 /*
@@ -878,8 +946,9 @@ do_dup(struct thread *td, int flags, int old, int new,
 	/*
 	 * Duplicate the source descriptor.
 	 */
+	seq_write_begin(&newfde->fde_seq);
 	filecaps_free(&newfde->fde_caps);
-	*newfde = *oldfde;
+	memcpy(fde_change(newfde), fde_change(oldfde), fde_change_size);
 	filecaps_copy(&oldfde->fde_caps, &newfde->fde_caps);
 	if ((flags & DUP_CLOEXEC) != 0)
 		newfde->fde_flags = oldfde->fde_flags | UF_EXCLOSE;
@@ -887,6 +956,7 @@ do_dup(struct thread *td, int flags, int old, int new,
 		newfde->fde_flags = oldfde->fde_flags & ~UF_EXCLOSE;
 	if (new > fdp->fd_lastfile)
 		fdp->fd_lastfile = new;
+	seq_write_end(&newfde->fde_seq);
 	*retval = new;
 
 	if (delfp != NULL) {
@@ -1753,6 +1823,7 @@ finstall(struct thread *td, struct file *fp, int *fd, int flags,
 	}
 	fhold(fp);
 	fde = &fdp->fd_ofiles[*fd];
+	seq_write_begin(&fde->fde_seq);
 	fde->fde_file = fp;
 	if ((flags & O_CLOEXEC) != 0)
 		fde->fde_flags |= UF_EXCLOSE;
@@ -1760,6 +1831,7 @@ finstall(struct thread *td, struct file *fp, int *fd, int flags,
 		filecaps_move(fcaps, &fde->fde_caps);
 	else
 		filecaps_fill(&fde->fde_caps);
+	seq_write_end(&fde->fde_seq);
 	FILEDESC_XUNLOCK(fdp);
 	return (0);
 }
@@ -2313,6 +2385,8 @@ fget_unlocked(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
 	cap_rights_t haverights;
 	int error;
 #endif
+	struct filedescent fde;
+	seq_t seq;
 
 	/*
 	 * Avoid reads reordering and then a first access to the
@@ -2329,19 +2403,21 @@ fget_unlocked(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
 	 * due to preemption.
 	 */
 	for (;;) {
-		fp = fdp->fd_ofiles[fd].fde_file;
+		seq = seq_read(fd_seq(fdp, fd));
+		fde = fdp->fd_ofiles[fd];
+		fp = fde.fde_file;
 		if (fp == NULL)
 			return (EBADF);
 #ifdef CAPABILITIES
-		haverights = *cap_rights(fdp, fd);
+		haverights = fde.fde_rights;
 		if (needrightsp != NULL) {
 			error = cap_check(&haverights, needrightsp);
-			if (error != 0)
-				return (error);
-			if (cap_rights_is_set(needrightsp, CAP_FCNTL)) {
+			if (error == 0 && cap_rights_is_set(needrightsp, CAP_FCNTL))
 				error = cap_fcntl_check(fdp, fd, needfcntl);
-				if (error != 0)
-					return (error);
+			if (error != 0) {
+				if (!seq_consistent(fd_seq(fdp, fd), seq))
+					continue;
+				return (error);
 			}
 		}
 #endif
@@ -2354,7 +2430,7 @@ fget_unlocked(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
 		 */
 		if (atomic_cmpset_acq_int(&fp->f_count, count, count + 1) != 1)
 			continue;
-		if (fp == fdp->fd_ofiles[fd].fde_file)
+		if (seq_consistent_nomb(fd_seq(fdp, fd), seq))
 			break;
 		fdrop(fp, curthread);
 	}
diff --git a/sys/sys/filedesc.h b/sys/sys/filedesc.h
index 516ef1b..84b38f2 100644
--- a/sys/sys/filedesc.h
+++ b/sys/sys/filedesc.h
@@ -42,6 +42,8 @@
 
 #include <machine/_limits.h>
 
+typedef uint32_t	seq_t;
+
 struct filecaps {
 	cap_rights_t	 fc_rights;	/* per-descriptor capability rights */
 	u_long		*fc_ioctls;	/* per-descriptor allowed ioctls */
@@ -50,6 +52,7 @@ struct filecaps {
 };
 
 struct filedescent {
+	seq_t		 fde_seq;
 	struct file	*fde_file;		/* file structure for open file */
 	struct filecaps	 fde_caps;		/* per-descriptor rights */
 	uint8_t		 fde_flags;		/* per-process open file flags */
@@ -58,6 +61,8 @@ struct filedescent {
 #define	fde_fcntls	fde_caps.fc_fcntls
 #define	fde_ioctls	fde_caps.fc_ioctls
 #define	fde_nioctls	fde_caps.fc_nioctls
+#define fde_change(fde)	((char *)(fde) + sizeof(seq_t))
+#define fde_change_size	(sizeof(struct filedescent) - sizeof(seq_t))
 
 /*
  * This structure is used for the management of descriptors.  It may be