diff --git a/sys/dev/hwpmc/hwpmc_mod.c b/sys/dev/hwpmc/hwpmc_mod.c
--- a/sys/dev/hwpmc/hwpmc_mod.c
+++ b/sys/dev/hwpmc/hwpmc_mod.c
@@ -212,7 +212,6 @@
 static int	pmc_attach_one_process(struct proc *p, struct pmc *pm);
 static int	pmc_can_allocate_rowindex(struct proc *p, unsigned int ri,
     int cpu);
-static int	pmc_can_attach(struct pmc *pm, struct proc *p);
 static void	pmc_capture_user_callchain(int cpu, int soft,
     struct trapframe *tf);
 static void	pmc_cleanup(void);
@@ -1029,61 +1028,6 @@
 	}
 }
 
-/*
- * Check if PMC 'pm' may be attached to target process 't'.
- */
-
-static int
-pmc_can_attach(struct pmc *pm, struct proc *t)
-{
-	struct proc *o;		/* pmc owner */
-	struct ucred *oc, *tc;	/* owner, target credentials */
-	int decline_attach, i;
-
-	/*
-	 * A PMC's owner can always attach that PMC to itself.
-	 */
-
-	if ((o = pm->pm_owner->po_owner) == t)
-		return 0;
-
-	PROC_LOCK(o);
-	oc = o->p_ucred;
-	crhold(oc);
-	PROC_UNLOCK(o);
-
-	PROC_LOCK(t);
-	tc = t->p_ucred;
-	crhold(tc);
-	PROC_UNLOCK(t);
-
-	/*
-	 * The effective uid of the PMC owner should match at least one
-	 * of the {effective,real,saved} uids of the target process.
-	 */
-
-	decline_attach = oc->cr_uid != tc->cr_uid &&
-	    oc->cr_uid != tc->cr_svuid &&
-	    oc->cr_uid != tc->cr_ruid;
-
-	/*
-	 * Every one of the target's group ids, must be in the owner's
-	 * group list.
-	 */
-	for (i = 0; !decline_attach && i < tc->cr_ngroups; i++)
-		decline_attach = !groupmember(tc->cr_groups[i], oc);
-
-	/* check the read and saved gids too */
-	if (decline_attach == 0)
-		decline_attach = !groupmember(tc->cr_rgid, oc) ||
-		    !groupmember(tc->cr_svgid, oc);
-
-	crfree(tc);
-	crfree(oc);
-
-	return !decline_attach;
-}
-
 /*
  * Attach a process to a PMC.
  */
@@ -1401,38 +1345,26 @@
 	if (freepath != NULL)
 		free(freepath, M_TEMP);
 
-	PMCDBG4(PRC,EXC,1, "exec proc=%p (%d, %s) cred-changed=%d",
-	    p, p->p_pid, p->p_comm, pk->pm_credentialschanged);
-
-	if (pk->pm_credentialschanged == 0) /* no change */
-		return;
+	PMCDBG3(PRC,EXC,1, "exec proc=%p (%d, %s)", p, p->p_pid, p->p_comm);
 
 	/*
-	 * If the newly exec()'ed process has a different credential
-	 * than before, allow it to be the target of a PMC only if
-	 * the PMC's owner has sufficient privilege.
+	 * For each PMC attached to the newly exec()'ed target process, the
+	 * owning process must have sufficient privilege to re-attach. If the
+	 * target process has different credentials than before the exec, or is
+	 * otherwise not considered 'debuggable' by the owner in question (e.g.
+	 * P2_NOTRACE is set for the process), then we may be forced to detach
+	 * one or more PMCs.
+	 *
+	 * This is analogous to the call to p_candebug() in the
+	 * PMC_OP_PMCATTACH path.
 	 */
 	for (ri = 0; ri < md->pmd_npmc; ri++) {
-		if ((pm = pp->pp_pmcs[ri].pp_pmc) != NULL) {
-			if (pmc_can_attach(pm, td->td_proc) != 0) {
-				pmc_detach_one_process(td->td_proc, pm,
-				    PMC_FLAG_NONE);
-			}
-		}
-	}
-
-	KASSERT(pp->pp_refcnt >= 0 && pp->pp_refcnt <= md->pmd_npmc,
-	    ("[pmc,%d] Illegal ref count %u on pp %p", __LINE__,
-		pp->pp_refcnt, pp));
+		if ((pm = pp->pp_pmcs[ri].pp_pmc) == NULL)
+			continue;
 
-	/*
-	 * If this process is no longer the target of any
-	 * PMCs, we can remove the process entry and free
-	 * up space.
-	 */
-	if (pp->pp_refcnt == 0) {
-		pmc_remove_process_descriptor(pp);
-		pmc_destroy_process_descriptor(pp);
+		po = pm->pm_owner;
+		if (p_candebug(FIRST_THREAD_IN_PROC(po->po_owner), p) != 0)
+			pmc_detach_one_process(p, pm, PMC_FLAG_REMOVE);
 	}
 }
 
diff --git a/sys/kern/kern_exec.c b/sys/kern/kern_exec.c
--- a/sys/kern/kern_exec.c
+++ b/sys/kern/kern_exec.c
@@ -918,7 +918,6 @@
 	 */
 	if (PMC_SYSTEM_SAMPLING_ACTIVE() || PMC_PROC_IS_USING_PMCS(p)) {
 		VOP_UNLOCK(imgp->vp);
-		pe.pm_credentialschanged = credential_changing;
 		pe.pm_entryaddr = imgp->entry_addr;
 
 		PMC_CALL_HOOK_X(td, PMC_FN_PROCESS_EXEC, (void *) &pe);
diff --git a/sys/sys/pmckern.h b/sys/sys/pmckern.h
--- a/sys/sys/pmckern.h
+++ b/sys/sys/pmckern.h
@@ -75,7 +75,6 @@
 } ring_type_t;
 
 struct pmckern_procexec {
-	int		pm_credentialschanged;
 	uintfptr_t	pm_entryaddr;
 };