Remove TCB_SUSPENDED constant and related code.

Since we no longer suspend waitpid'ing tracees, we have only one case when
we suspend tracee: when we pick up a new tracee created by clone/fork/vfork.

Background: on some other OSes, attach to child is done this way:
get fork's result (pid), loop ptrace(PTRACE_ATTACH) until you hook up
new process/thread. This is ugly and not safe, but what matters for us
is that it doesn't require suspending. Suspending is required
on Linux only, because on Linux attach to child is done differently.

On Linux, we use two methods of catching new tracee:
adding CLONE_THREAD bit to syscall (if needed, we change
[v]fork into clone before that), or using ptrace options.
In both cases, it may be so that new tracee appears before one which
created it returns from syscall. In this case, current code
suspends new tracee until its creator returns. Only then
strace can determine who is its parent (it needs child's pid for this,
which is visible in parent's [v]fork/clone result).
This is inherently racy. For example, what if SIGKILL kills
creator after it succeeded creating child, but before it returns?
Looks like we will have child suspended forever.

But after previous commit, we DO NOT NEED parent<->child link for anything.
Therefore we do not need suspending too. Bingo!

This patch removes suspending code. Now new tracees will be continued
right away. Next patch will remove tcp->parent member.

* defs.h: Remove TCB_SUSPENDED constant
* process.c (handle_new_child): Delete this function.
  (internal_fork): Do not call handle_new_child on syscall exit.
* strace.c (handle_ptrace_event): Delete this function.
  (trace): Do not suspend new child; remove all handling
  of now impossible TCB_SUSPENDED condition.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>

1 files changed, 0 insertions, 1 deletions

diff --git a/defs.h b/defs.h
index bd793a1..7356fe5 100644
--- a/defs.h
+++ b/defs.h
@@ -411,7 +411,6 @@ struct tcb {
 #define TCB_INUSE	00002	/* This table entry is in use */
 #define TCB_INSYSCALL	00004	/* A system call is in progress */
 #define TCB_ATTACHED	00010	/* Process is not our own child */
-#define TCB_SUSPENDED	00040	/* Process can not be allowed to resume just now */
 #define TCB_BPTSET	00100	/* "Breakpoint" set after fork(2) */
 #define TCB_SIGTRAPPED	00200	/* Process wanted to block SIGTRAP */
 #define TCB_REPRINT	01000	/* We should reprint this syscall on exit */