[src/trunk]: src/sys Implement a simple psref leak detector

[ozaki-r <ozaki-r%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/2bea9a2f032a
branches:  trunk
changeset: 455940:2bea9a2f032a
user:      ozaki-r <ozaki-r%NetBSD.org@localhost>
date:      Fri Apr 19 01:52:55 2019 +0000

description:
Implement a simple psref leak detector

It detects leaks by counting up the number of held psref by an LWP and checking
its zeroness at the end of syscalls and softint handlers.  For the counter, a
unused field of struct lwp is reused.

The detector runs only if DIAGNOSTIC is turned on.

diffstat:

 sys/kern/kern_lwp.c                      |   5 +++--
 sys/kern/kern_softint.c                  |   7 +++++--
 sys/kern/subr_psref.c                    |  17 +++++++++++++++--
 sys/rump/kern/lib/libsysproxy/sysproxy.c |   5 +++--
 sys/sys/lwp.h                            |   4 ++--
 sys/sys/userret.h                        |   3 ++-
 6 files changed, 30 insertions(+), 11 deletions(-)

diffs (167 lines):

diff -r 635f5818a0cc -r 2bea9a2f032a sys/kern/kern_lwp.c
--- a/sys/kern/kern_lwp.c       Thu Apr 18 22:49:08 2019 +0000
+++ b/sys/kern/kern_lwp.c       Fri Apr 19 01:52:55 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_lwp.c,v 1.196 2019/03/01 09:02:03 hannken Exp $   */
+/*     $NetBSD: kern_lwp.c,v 1.197 2019/04/19 01:52:55 ozaki-r Exp $   */
 
 /*-
  * Copyright (c) 2001, 2006, 2007, 2008, 2009 The NetBSD Foundation, Inc.
@@ -211,7 +211,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_lwp.c,v 1.196 2019/03/01 09:02:03 hannken Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_lwp.c,v 1.197 2019/04/19 01:52:55 ozaki-r Exp $");
 
 #include "opt_ddb.h"
 #include "opt_lockdebug.h"
@@ -836,6 +836,7 @@
        l2->l_flag = 0;
        l2->l_pflag = LP_MPSAFE;
        TAILQ_INIT(&l2->l_ld_locks);
+       l2->l_psrefs = 0;
 
        /*
         * For vfork, borrow parent's lwpctl context if it exists.
diff -r 635f5818a0cc -r 2bea9a2f032a sys/kern/kern_softint.c
--- a/sys/kern/kern_softint.c   Thu Apr 18 22:49:08 2019 +0000
+++ b/sys/kern/kern_softint.c   Fri Apr 19 01:52:55 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_softint.c,v 1.45 2017/12/28 03:39:48 msaitoh Exp $        */
+/*     $NetBSD: kern_softint.c,v 1.46 2019/04/19 01:52:55 ozaki-r Exp $        */
 
 /*-
  * Copyright (c) 2007, 2008 The NetBSD Foundation, Inc.
@@ -170,7 +170,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_softint.c,v 1.45 2017/12/28 03:39:48 msaitoh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_softint.c,v 1.46 2019/04/19 01:52:55 ozaki-r Exp $");
 
 #include <sys/param.h>
 #include <sys/proc.h>
@@ -595,6 +595,9 @@
                KASSERTMSG(curcpu()->ci_mtx_count == 0,
                    "%s: ci_mtx_count (%d) != 0, sh_func %p\n",
                    __func__, curcpu()->ci_mtx_count, sh->sh_func);
+               /* Diagnostic: check that psrefs have not leaked. */
+               KASSERTMSG(l->l_psrefs == 0, "%s: l_psrefs=%d, sh_func=%p\n",
+                   __func__, l->l_psrefs, sh->sh_func);
 
                (void)splhigh();
                KASSERT((sh->sh_flags & SOFTINT_ACTIVE) != 0);
diff -r 635f5818a0cc -r 2bea9a2f032a sys/kern/subr_psref.c
--- a/sys/kern/subr_psref.c     Thu Apr 18 22:49:08 2019 +0000
+++ b/sys/kern/subr_psref.c     Fri Apr 19 01:52:55 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: subr_psref.c,v 1.11 2018/02/01 03:17:00 ozaki-r Exp $  */
+/*     $NetBSD: subr_psref.c,v 1.12 2019/04/19 01:52:55 ozaki-r Exp $  */
 
 /*-
  * Copyright (c) 2016 The NetBSD Foundation, Inc.
@@ -64,7 +64,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: subr_psref.c,v 1.11 2018/02/01 03:17:00 ozaki-r Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_psref.c,v 1.12 2019/04/19 01:52:55 ozaki-r Exp $");
 
 #include <sys/types.h>
 #include <sys/condvar.h>
@@ -278,6 +278,10 @@
        /* Release the CPU list and restore interrupts.  */
        percpu_putref(class->prc_percpu);
        splx(s);
+
+#ifdef DIAGNOSTIC
+       curlwp->l_psrefs++;
+#endif
 }
 
 /*
@@ -332,6 +336,11 @@
        percpu_putref(class->prc_percpu);
        splx(s);
 
+#ifdef DIAGNOSTIC
+       KASSERT(curlwp->l_psrefs > 0);
+       curlwp->l_psrefs--;
+#endif
+
        /* If someone is waiting for users to drain, notify 'em.  */
        if (__predict_false(target->prt_draining))
                cv_broadcast(&class->prc_cv);
@@ -388,6 +397,10 @@
        /* Release the CPU list and restore interrupts.  */
        percpu_putref(class->prc_percpu);
        splx(s);
+
+#ifdef DIAGNOSTIC
+       curlwp->l_psrefs++;
+#endif
 }
 
 /*
diff -r 635f5818a0cc -r 2bea9a2f032a sys/rump/kern/lib/libsysproxy/sysproxy.c
--- a/sys/rump/kern/lib/libsysproxy/sysproxy.c  Thu Apr 18 22:49:08 2019 +0000
+++ b/sys/rump/kern/lib/libsysproxy/sysproxy.c  Fri Apr 19 01:52:55 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sysproxy.c,v 1.5 2019/04/18 08:31:44 ozaki-r Exp $     */
+/*     $NetBSD: sysproxy.c,v 1.6 2019/04/19 01:52:55 ozaki-r Exp $     */
 
 /*
  * Copyright (c) 2010, 2011 Antti Kantee.  All Rights Reserved.
@@ -26,7 +26,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sysproxy.c,v 1.5 2019/04/18 08:31:44 ozaki-r Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sysproxy.c,v 1.6 2019/04/19 01:52:55 ozaki-r Exp $");
 
 #include <sys/param.h>
 #include <sys/filedesc.h>
@@ -77,6 +77,7 @@
        /* Sanity checks (from mi_userret) */
        LOCKDEBUG_BARRIER(NULL, 0);
        KASSERT(l->l_nopreempt == 0);
+       KASSERT(l->l_psrefs == 0);
 
        return rv;
 }
diff -r 635f5818a0cc -r 2bea9a2f032a sys/sys/lwp.h
--- a/sys/sys/lwp.h     Thu Apr 18 22:49:08 2019 +0000
+++ b/sys/sys/lwp.h     Fri Apr 19 01:52:55 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: lwp.h,v 1.181 2019/03/01 09:02:03 hannken Exp $        */
+/*     $NetBSD: lwp.h,v 1.182 2019/04/19 01:52:55 ozaki-r Exp $        */
 
 /*
  * Copyright (c) 2001, 2006, 2007, 2008, 2009, 2010
@@ -184,7 +184,7 @@
        u_int           l_cv_signalled; /* c: restarted by cv_signal() */
        u_short         l_shlocks;      /* !: lockdebug: shared locks held */
        u_short         l_exlocks;      /* !: lockdebug: excl. locks held */
-       u_short         l_unused;       /* !: unused */
+       u_short         l_psrefs;       /* !: count of psref held */
        u_short         l_blcnt;        /* !: count of kernel_lock held */
        int             l_nopreempt;    /* !: don't preempt me! */
        u_int           l_dopreempt;    /* s: kernel preemption pending */
diff -r 635f5818a0cc -r 2bea9a2f032a sys/sys/userret.h
--- a/sys/sys/userret.h Thu Apr 18 22:49:08 2019 +0000
+++ b/sys/sys/userret.h Fri Apr 19 01:52:55 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: userret.h,v 1.26 2013/04/07 07:54:53 kiyohara Exp $    */
+/*     $NetBSD: userret.h,v 1.27 2019/04/19 01:52:55 ozaki-r Exp $     */
 
 /*-
  * Copyright (c) 1998, 2000, 2003, 2006, 2008 The NetBSD Foundation, Inc.
@@ -114,6 +114,7 @@
 
        LOCKDEBUG_BARRIER(NULL, 0);
        KASSERT(l->l_nopreempt == 0);
+       KASSERT(l->l_psrefs == 0);
 }
 
 #endif /* !_SYS_USERRET_H_ */