diff --git a/sys/kern/kern_ktrace.c b/sys/kern/kern_ktrace.c
index a377001760b9..1dfc237dda37 100644
--- a/sys/kern/kern_ktrace.c
+++ b/sys/kern/kern_ktrace.c
@@ -807,7 +807,7 @@ ktr_psig(int sig, sig_t action, const sigset_t *mask,
 }
 
 void
-ktr_csw(int out, int user)
+ktr_csw(int out, int user, const struct syncobj *syncobj)
 {
 	lwp_t *l = curlwp;
 	struct proc *p = l->l_proc;
@@ -819,9 +819,11 @@ ktr_csw(int out, int user)
 
 	/*
 	 * Don't record context switches resulting from blocking on
-	 * locks; it's too easy to get duff results.
+	 * locks; the results are not useful, and the mutex may be in a
+	 * softint, which would lead us to ktealloc in softint context,
+	 * which is forbidden.
 	 */
-	if (l->l_syncobj == &mutex_syncobj || l->l_syncobj == &rw_syncobj)
+	if (syncobj == &mutex_syncobj || syncobj == &rw_syncobj)
 		return;
 
 	/*
diff --git a/sys/kern/kern_sleepq.c b/sys/kern/kern_sleepq.c
index c5c86e5a755b..23b5635fd726 100644
--- a/sys/kern/kern_sleepq.c
+++ b/sys/kern/kern_sleepq.c
@@ -309,6 +309,7 @@ sleepq_block(int timo, bool catch_p)
 	lwp_t *l = curlwp;
 	bool early = false;
 	int biglocks = l->l_biglocks;
+	struct syncobj *syncobj = l->l_syncobj;
 
 	KASSERTMSG(l->l_blcnt == 0, "unexpectedly acquired %d biglocks",
 	    l->l_blcnt);
@@ -321,7 +322,7 @@ sleepq_block(int timo, bool catch_p)
 	 */
 	l->l_biglocks = -1;
 
-	ktrcsw(1, 0);
+	ktrcsw(1, 0, syncobj);
 
 	/*
 	 * If sleeping interruptably, check for pending signals, exits or
@@ -408,7 +409,7 @@ sleepq_block(int timo, bool catch_p)
 		}
 	}
 
-	ktrcsw(0, 0);
+	ktrcsw(0, 0, syncobj);
 	KASSERTMSG(l->l_blcnt == 0, "unexpectedly acquired %d biglocks",
 	    l->l_blcnt);
 	if (__predict_false(biglocks != 0)) {
diff --git a/sys/sys/ktrace.h b/sys/sys/ktrace.h
index 0a74223b9dcb..18a0fea03380 100644
--- a/sys/sys/ktrace.h
+++ b/sys/sys/ktrace.h
@@ -297,6 +297,8 @@ __END_DECLS
 
 #else
 
+struct syncobj;
+
 void ktrinit(void);
 void ktrderef(struct proc *);
 void ktradref(struct proc *);
@@ -307,7 +309,7 @@ extern int ktrace_on;
 int ktruser(const char *, void *, size_t, int);
 bool ktr_point(int);
 
-void ktr_csw(int, int);
+void ktr_csw(int, int, const struct syncobj *);
 void ktr_emul(void);
 void ktr_geniov(int, enum uio_rw, struct iovec *, size_t, int);
 void ktr_genio(int, enum uio_rw, const void *, size_t, int);
@@ -349,10 +351,10 @@ ktrpoint(int fac)
 }
 
 static __inline void
-ktrcsw(int a, int b)
+ktrcsw(int a, int b, const struct syncobj *c)
 {
 	if (__predict_false(ktrace_on))
-		ktr_csw(a, b);
+		ktr_csw(a, b, c);
 }
 
 static __inline void