[src/trunk]: src/sys Refactor sigswitch()

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

details:   https://anonhg.NetBSD.org/src/rev/fd8e3d06d020
branches:  trunk
changeset: 455278:fd8e3d06d020
user:      kamil <kamil%NetBSD.org@localhost>
date:      Sat Oct 12 19:57:09 2019 +0000

description:
Refactor sigswitch()

Make the function static as it is now local to kern_sig.c.

Rename the 'relock' argument to 'proc_lock_held' as it is more verbose.
This was suggested by mjg@freebsd. While there this flips the users between
true<->false.

Add additional KASSERT(9) calls here to validate whethe proc_lock is used
accordingly.

diffstat:

 sys/kern/kern_sig.c |  38 +++++++++++++++++++++++---------------
 sys/sys/signalvar.h |   3 +--
 2 files changed, 24 insertions(+), 17 deletions(-)

diffs (174 lines):

diff -r c610775a4cc7 -r fd8e3d06d020 sys/kern/kern_sig.c
--- a/sys/kern/kern_sig.c       Sat Oct 12 19:38:57 2019 +0000
+++ b/sys/kern/kern_sig.c       Sat Oct 12 19:57:09 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_sig.c,v 1.368 2019/10/12 10:55:23 kamil Exp $     */
+/*     $NetBSD: kern_sig.c,v 1.369 2019/10/12 19:57:09 kamil Exp $     */
 
 /*-
  * Copyright (c) 2006, 2007, 2008 The NetBSD Foundation, Inc.
@@ -70,7 +70,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_sig.c,v 1.368 2019/10/12 10:55:23 kamil Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_sig.c,v 1.369 2019/10/12 19:57:09 kamil Exp $");
 
 #include "opt_ptrace.h"
 #include "opt_dtrace.h"
@@ -125,6 +125,7 @@
 static int     sigpost(struct lwp *, sig_t, int, int);
 static int     sigput(sigpend_t *, struct proc *, ksiginfo_t *);
 static int     sigunwait(struct proc *, const ksiginfo_t *);
+static void    sigswitch(int, int, bool);
 
 static void    sigacts_poolpage_free(struct pool *, void *);
 static void    *sigacts_poolpage_alloc(struct pool *, int);
@@ -931,7 +932,7 @@
         * The process is already stopping.
         */
        if ((p->p_sflag & PS_STOPPING) != 0) {
-               sigswitch(0, p->p_xsig, false);
+               sigswitch(0, p->p_xsig, true);
                mutex_enter(proc_lock);
                mutex_enter(p->p_lock);
                goto repeat; /* XXX */
@@ -949,7 +950,7 @@
                p->p_sigctx.ps_faked = true;
                p->p_sigctx.ps_lwp = ksi->ksi_lid;
                p->p_sigctx.ps_info = ksi->ksi_info;
-               sigswitch(0, signo, false);
+               sigswitch(0, signo, true);
 
                if (ktrpoint(KTR_PSIG)) {
                        if (p->p_emul->e_ktrpsig)
@@ -1641,7 +1642,7 @@
         * The process is already stopping.
         */
        if ((p->p_sflag & PS_STOPPING) != 0) {
-               sigswitch(0, p->p_xsig, false);
+               sigswitch(0, p->p_xsig, true);
                mutex_enter(proc_lock);
                mutex_enter(p->p_lock);
                goto repeat; /* XXX */
@@ -1666,7 +1667,7 @@
        p->p_sigctx.ps_lwp = ksi.ksi_lid;
        p->p_sigctx.ps_info = ksi.ksi_info;
 
-       sigswitch(0, signo, false);
+       sigswitch(0, signo, true);
 
        if (code == TRAP_CHLD) {
                mutex_enter(proc_lock);
@@ -1686,8 +1687,8 @@
 /*
  * Stop the current process and switch away when being stopped or traced.
  */
-void
-sigswitch(int ppmask, int signo, bool relock)
+static void
+sigswitch(int ppmask, int signo, bool proc_lock_held)
 {
        struct lwp *l = curlwp;
        struct proc *p = l->l_proc;
@@ -1697,6 +1698,12 @@
        KASSERT(l->l_stat == LSONPROC);
        KASSERT(p->p_nrlwps > 0);
 
+       if (proc_lock_held) {
+               KASSERT(mutex_owned(proc_lock));
+       } else {
+               KASSERT(!mutex_owned(proc_lock));
+       }
+
        /*
         * If we are exiting, demise now.
         *
@@ -1704,7 +1711,7 @@
         */
        if (__predict_false(ISSET(p->p_sflag, PS_WEXIT))) {
                mutex_exit(p->p_lock);
-               if (!relock) {
+               if (proc_lock_held) {
                        mutex_exit(proc_lock);
                }
                lwp_exit(l);
@@ -1728,7 +1735,7 @@
         * a new signal, then signal the parent.
         */
        if ((p->p_sflag & PS_STOPPING) != 0) {
-               if (relock && !mutex_tryenter(proc_lock)) {
+               if (!proc_lock_held && !mutex_tryenter(proc_lock)) {
                        mutex_exit(p->p_lock);
                        mutex_enter(proc_lock);
                        mutex_enter(p->p_lock);
@@ -1748,6 +1755,7 @@
        /*
         * Unlock and switch away.
         */
+       KASSERT(!mutex_owned(proc_lock));
        KERNEL_UNLOCK_ALL(l, &biglocks);
        if (p->p_stat == SSTOP || (p->p_sflag & PS_STOPPING) != 0) {
                p->p_nrlwps--;
@@ -1837,7 +1845,7 @@
                 * we awaken, check for a signal from the debugger.
                 */
                if (p->p_stat == SSTOP || (p->p_sflag & PS_STOPPING) != 0) {
-                       sigswitch(PS_NOCLDSTOP, 0, true);
+                       sigswitch(PS_NOCLDSTOP, 0, false);
                        mutex_enter(p->p_lock);
                        signo = sigchecktrace();
                } else if (p->p_stat == SACTIVE)
@@ -1909,7 +1917,7 @@
                        p->p_xsig = signo;
 
                        /* Handling of signal trace */
-                       sigswitch(0, signo, true);
+                       sigswitch(0, signo, false);
                        mutex_enter(p->p_lock);
 
                        /* Check for a signal from the debugger. */
@@ -1966,7 +1974,7 @@
                                p->p_xsig = signo;
                                p->p_sflag &= ~PS_CONTINUED;
                                signo = 0;
-                               sigswitch(PS_NOCLDSTOP, p->p_xsig, true);
+                               sigswitch(PS_NOCLDSTOP, p->p_xsig, false);
                                mutex_enter(p->p_lock);
                        } else if (prop & SA_IGNORE) {
                                /*
@@ -2519,7 +2527,7 @@
         * The process is already stopping.
         */
        if ((p->p_sflag & PS_STOPPING) != 0) {
-               sigswitch(0, p->p_xsig, true);
+               sigswitch(0, p->p_xsig, false);
                mutex_enter(p->p_lock);
                goto repeat; /* XXX */
        }
@@ -2532,7 +2540,7 @@
        p->p_xsig = signo;
        p->p_sigctx.ps_lwp = ksi.ksi_lid;
        p->p_sigctx.ps_info = ksi.ksi_info;
-       sigswitch(0, signo, true);
+       sigswitch(0, signo, false);
 
        if (ktrpoint(KTR_PSIG)) {
                if (p->p_emul->e_ktrpsig)
diff -r c610775a4cc7 -r fd8e3d06d020 sys/sys/signalvar.h
--- a/sys/sys/signalvar.h       Sat Oct 12 19:38:57 2019 +0000
+++ b/sys/sys/signalvar.h       Sat Oct 12 19:57:09 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: signalvar.h,v 1.96 2019/09/30 21:13:33 kamil Exp $     */
+/*     $NetBSD: signalvar.h,v 1.97 2019/10/12 19:57:09 kamil Exp $     */
 
 /*
  * Copyright (c) 1991, 1993
@@ -153,7 +153,6 @@
 int    killpg1(struct lwp *, struct ksiginfo *, int, int);
 void   proc_unstop(struct proc *p);
 void   eventswitch(int, int, int);
-void   sigswitch(int, int, bool);
 
 
 int    sigaction1(struct lwp *, int, const struct sigaction *,