The initial kd_lookup() in kcovopen() is redundant as kcov is a cloning

device. Turn it into an assertion instead to better state the expected
semantics of D_CLONE.

Prompted after a discussion with visa@

diff --git a/sys/dev/kcov.c b/sys/dev/kcov.c
index 0a130fd..5db7e76 100644 (file)
--- a/sys/dev/kcov.c
+++ b/sys/dev/kcov.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: kcov.c,v 1.42 2021/12/27 15:38:25 anton Exp $ */
+/*     $OpenBSD: kcov.c,v 1.43 2021/12/28 17:50:10 anton Exp $ */
 
 /*
  * Copyright (c) 2018 Anton Lindqvist <anton@openbsd.org>
@@ -53,7 +53,7 @@
 struct kcov_dev {
        int              kd_state;      /* [M] */
        int              kd_mode;       /* [M] */
-       int              kd_unit;       /* [I] device minor */
+       int              kd_unit;       /* [I] D_CLONE unique device minor */
        int              kd_intr;       /* [M] currently used in interrupt */
        uintptr_t       *kd_buf;        /* [a] traced coverage */
        size_t           kd_nmemb;      /* [I] */
@@ -290,21 +290,13 @@ kcovopen(dev_t dev, int flag, int mode, struct proc *p)
 {
        struct kcov_dev *kd;
 
-       mtx_enter(&kcov_mtx);
-
-       if (kd_lookup(minor(dev)) != NULL) {
-               mtx_leave(&kcov_mtx);
-               return (EBUSY);
-       }
-
-       if (kcov_cold)
-               kcov_cold = 0;
-
-       mtx_leave(&kcov_mtx);
        kd = malloc(sizeof(*kd), M_SUBPROC, M_WAITOK | M_ZERO);
        kd->kd_unit = minor(dev);
        mtx_enter(&kcov_mtx);
+       KASSERT(kd_lookup(kd->kd_unit) == NULL);
        TAILQ_INSERT_TAIL(&kd_list, kd, kd_entry);
+       if (kcov_cold)
+               kcov_cold = 0;
        mtx_leave(&kcov_mtx);
        return (0);
 }