Kill SINGLE_PTRACE and use SINGLE_SUSPEND which has almost the same semantic.

single_thread_set() is modified to explicitly indicated when waiting until
sibling threads are parked is required.  This is obviously not required if
a traced thread is switching away from a CPU after handling a STOP signal.

ok claudio@

3 files changed, 10 insertions, 14 deletions

diff --git a/sys/kern/kern_exec.c b/sys/kern/kern_exec.c
index 8f5e05aac67..192d5e66ff6 100644
--- a/sys/kern/kern_exec.c
+++ b/sys/kern/kern_exec.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_exec.c,v 1.219 2020/10/15 16:31:11 cheloha Exp $	*/
+/*	$OpenBSD: kern_exec.c,v 1.220 2021/03/08 10:12:05 mpi Exp $	*/
 /*	$NetBSD: kern_exec.c,v 1.75 1996/02/09 18:59:28 christos Exp $	*/
 
 /*-
@@ -432,7 +432,7 @@ sys_execve(struct proc *p, void *v, register_t *retval)
 	 * we're committed: any further errors will kill the process, so
 	 * kill the other threads now.
 	 */
-	single_thread_set(p, SINGLE_EXIT, 0);
+	single_thread_set(p, SINGLE_EXIT, 1);
 
 	/*
 	 * Prepare vmspace for remapping. Note that uvmspace_exec can replace
diff --git a/sys/kern/kern_exit.c b/sys/kern/kern_exit.c
index cbb116e6dcc..fa72891271e 100644
--- a/sys/kern/kern_exit.c
+++ b/sys/kern/kern_exit.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_exit.c,v 1.196 2021/02/15 09:35:59 mpi Exp $	*/
+/*	$OpenBSD: kern_exit.c,v 1.197 2021/03/08 10:12:05 mpi Exp $	*/
 /*	$NetBSD: kern_exit.c,v 1.39 1996/04/22 01:38:25 christos Exp $	*/
 
 /*
@@ -136,7 +136,7 @@ exit1(struct proc *p, int xexit, int xsig, int flags)
 	} else {
 		/* nope, multi-threaded */
 		if (flags == EXIT_NORMAL)
-			single_thread_set(p, SINGLE_EXIT, 0);
+			single_thread_set(p, SINGLE_EXIT, 1);
 		else if (flags == EXIT_THREAD)
 			single_thread_check(p, 0);
 	}
diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
index 8f957beab20..d4f87e7c68f 100644
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_sig.c,v 1.274 2021/03/04 09:02:37 mpi Exp $	*/
+/*	$OpenBSD: kern_sig.c,v 1.275 2021/03/08 10:12:05 mpi Exp $	*/
 /*	$NetBSD: kern_sig.c,v 1.54 1996/04/22 01:38:32 christos Exp $	*/
 
 /*
@@ -1490,7 +1490,7 @@ sigexit(struct proc *p, int signum)
 
 		/* if there are other threads, pause them */
 		if (P_HASSIBLING(p))
-			single_thread_set(p, SINGLE_SUSPEND, 0);
+			single_thread_set(p, SINGLE_SUSPEND, 1);
 
 		if (coredump(p) == 0)
 			signum |= WCOREFLAG;
@@ -2000,14 +2000,12 @@ single_thread_check(struct proc *p, int deep)
  * where the other threads should stop:
  *  - SINGLE_SUSPEND: stop wherever they are, will later either be told to exit
  *    (by setting to SINGLE_EXIT) or be released (via single_thread_clear())
- *  - SINGLE_PTRACE: stop wherever they are, will wait for them to stop
- *    later (via single_thread_wait()) and released as with SINGLE_SUSPEND
  *  - SINGLE_UNWIND: just unwind to kernel boundary, will be told to exit
  *    or released as with SINGLE_SUSPEND
  *  - SINGLE_EXIT: unwind to kernel boundary and exit
  */
 int
-single_thread_set(struct proc *p, enum single_thread_mode mode, int deep)
+single_thread_set(struct proc *p, enum single_thread_mode mode, int wait)
 {
 	struct process *pr = p->p_p;
 	struct proc *q;
@@ -2016,7 +2014,7 @@ single_thread_set(struct proc *p, enum single_thread_mode mode, int deep)
 	KASSERT(curproc == p);
 
 	SCHED_LOCK(s);
-	error = single_thread_check_locked(p, deep, s);
+	error = single_thread_check_locked(p, (mode == SINGLE_UNWIND), s);
 	if (error) {
 		SCHED_UNLOCK(s);
 		return error;
@@ -2024,7 +2022,6 @@ single_thread_set(struct proc *p, enum single_thread_mode mode, int deep)
 
 	switch (mode) {
 	case SINGLE_SUSPEND:
-	case SINGLE_PTRACE:
 		break;
 	case SINGLE_UNWIND:
 		atomic_setbits_int(&pr->ps_flags, PS_SINGLEUNWIND);
@@ -2063,8 +2060,7 @@ single_thread_set(struct proc *p, enum single_thread_mode mode, int deep)
 			/* if it's not interruptible, then just have to wait */
 			if (q->p_flag & P_SINTR) {
 				/* merely need to suspend?  just stop it */
-				if (mode == SINGLE_SUSPEND ||
-				    mode == SINGLE_PTRACE) {
+				if (mode == SINGLE_SUSPEND) {
 					q->p_stat = SSTOP;
 					break;
 				}
@@ -2089,7 +2085,7 @@ single_thread_set(struct proc *p, enum single_thread_mode mode, int deep)
 	}
 	SCHED_UNLOCK(s);
 
-	if (mode != SINGLE_PTRACE)
+	if (wait)
 		single_thread_wait(pr, 1);
 
 	return 0;