[src/trunk]: src/sys/kern If we go to allocate and find someone else has at t...

[dholland <dholland%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/193715be66ef
branches:  trunk
changeset: 356025:193715be66ef
user:      dholland <dholland%NetBSD.org@localhost>
date:      Mon Aug 28 04:57:11 2017 +0000

description:
If we go to allocate and find someone else has at the same time, don't
trigger a refcount leak of the other guy's object. From mjg@freebsd.

While here also remove a bogus use of lbolt on the same path.

diffstat:

 sys/kern/kern_ktrace.c |  61 ++++++++++++++++++++++++-------------------------
 1 files changed, 30 insertions(+), 31 deletions(-)

diffs (111 lines):

diff -r 04fd7d2a3377 -r 193715be66ef sys/kern/kern_ktrace.c
--- a/sys/kern/kern_ktrace.c    Mon Aug 28 01:34:52 2017 +0000
+++ b/sys/kern/kern_ktrace.c    Mon Aug 28 04:57:11 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_ktrace.c,v 1.171 2017/07/28 15:16:39 riastradh Exp $      */
+/*     $NetBSD: kern_ktrace.c,v 1.172 2017/08/28 04:57:11 dholland Exp $       */
 
 /*-
  * Copyright (c) 2006, 2007, 2008 The NetBSD Foundation, Inc.
@@ -61,7 +61,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_ktrace.c,v 1.171 2017/07/28 15:16:39 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_ktrace.c,v 1.172 2017/08/28 04:57:11 dholland Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -985,7 +985,7 @@
 {
        struct proc *p;
        struct pgrp *pg;
-       struct ktr_desc *ktd = NULL;
+       struct ktr_desc *ktd = NULL, *nktd;
        file_t *fp = *fpp;
        int ret = 0;
        int error = 0;
@@ -1015,22 +1015,22 @@
                ktd = ktd_lookup(fp);
                mutex_exit(&ktrace_lock);
                if (ktd == NULL) {
-                       ktd = kmem_alloc(sizeof(*ktd), KM_SLEEP);
-                       TAILQ_INIT(&ktd->ktd_queue);
-                       callout_init(&ktd->ktd_wakch, CALLOUT_MPSAFE);
-                       cv_init(&ktd->ktd_cv, "ktrwait");
-                       cv_init(&ktd->ktd_sync_cv, "ktrsync");
-                       ktd->ktd_flags = 0;
-                       ktd->ktd_qcount = 0;
-                       ktd->ktd_error = 0;
-                       ktd->ktd_errcnt = 0;
-                       ktd->ktd_delayqcnt = ktd_delayqcnt;
-                       ktd->ktd_wakedelay = mstohz(ktd_wakedelay);
-                       ktd->ktd_intrwakdl = mstohz(ktd_intrwakdl);
-                       ktd->ktd_ref = 0;
-                       ktd->ktd_fp = fp;
+                       nktd = kmem_alloc(sizeof(*nktd), KM_SLEEP);
+                       TAILQ_INIT(&nktd->ktd_queue);
+                       callout_init(&nktd->ktd_wakch, CALLOUT_MPSAFE);
+                       cv_init(&nktd->ktd_cv, "ktrwait");
+                       cv_init(&nktd->ktd_sync_cv, "ktrsync");
+                       nktd->ktd_flags = 0;
+                       nktd->ktd_qcount = 0;
+                       nktd->ktd_error = 0;
+                       nktd->ktd_errcnt = 0;
+                       nktd->ktd_delayqcnt = ktd_delayqcnt;
+                       nktd->ktd_wakedelay = mstohz(ktd_wakedelay);
+                       nktd->ktd_intrwakdl = mstohz(ktd_intrwakdl);
+                       nktd->ktd_ref = 0;
+                       nktd->ktd_fp = fp;
                        mutex_enter(&ktrace_lock);
-                       ktdref(ktd);
+                       ktdref(nktd);
                        mutex_exit(&ktrace_lock);
 
                        /*
@@ -1038,16 +1038,16 @@
                         * whether ktruss or ktrace.
                         */
                        if (fp->f_type == DTYPE_PIPE)
-                               ktd->ktd_flags |= KTDF_INTERACTIVE;
+                               nktd->ktd_flags |= KTDF_INTERACTIVE;
 
                        mutex_enter(&fp->f_lock);
                        fp->f_count++;
                        mutex_exit(&fp->f_lock);
                        error = kthread_create(PRI_NONE, KTHREAD_MPSAFE, NULL,
-                           ktrace_thread, ktd, &ktd->ktd_lwp, "ktrace");
+                           ktrace_thread, nktd, &nktd->ktd_lwp, "ktrace");
                        if (error != 0) {
-                               kmem_free(ktd, sizeof(*ktd));
-                               ktd = NULL;
+                               kmem_free(nktd, sizeof(*nktd));
+                               nktd = NULL;
                                mutex_enter(&fp->f_lock);
                                fp->f_count--;
                                mutex_exit(&fp->f_lock);
@@ -1055,16 +1055,15 @@
                        }
 
                        mutex_enter(&ktrace_lock);
-                       if (ktd_lookup(fp) != NULL) {
-                               ktdrel(ktd);
-                               ktd = NULL;
-                       } else
-                               TAILQ_INSERT_TAIL(&ktdq, ktd, ktd_list);
-                       if (ktd == NULL)
-                               cv_wait(&lbolt, &ktrace_lock);
+                       ktd = ktd_lookup(fp);
+                       if (ktd != NULL) {
+                               ktdrel(nktd);
+                               nktd = NULL;
+                       } else {
+                               TAILQ_INSERT_TAIL(&ktdq, nktd, ktd_list);
+                               ktd = nktd;
+                       }
                        mutex_exit(&ktrace_lock);
-                       if (ktd == NULL)
-                               goto done;
                }
                break;