[PATCH] Remove TCB_FOLLOWFORK

[Denys Vlasenko]

Hi,

TCB_FOLLOWFORK flag seems to be unnecessary, because we either follow
all [v]forks/clones or don't follow any, therefore global variable
followfork is an already existing indicator of what we want to do.

This patch drops all setting/clearing of TCB_FOLLOWFORK bit,
and replaces checks for this bit by checks of followfork value.

In internal_fork, check is moved to in front of if(), since
the check is needed on both "entering" and "exiting" branch.

Please review.
-- 
vda



diff -d -urpN strace.5/defs.h strace.6/defs.h
--- strace.5/defs.h	2011-06-21 20:26:28.000000000 +0200
+++ strace.6/defs.h	2011-06-22 13:31:45.323884488 +0200
@@ -401,7 +401,6 @@ struct tcb {
 #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_FOLLOWFORK	00400	/* Process should have forks followed */
 #define TCB_REPRINT	01000	/* We should reprint this syscall on exit */
 #define TCB_FILTERED	02000	/* This system call has been filtered out */
 #ifdef LINUX
diff -d -urpN strace.5/process.c strace.6/process.c
--- strace.5/process.c	2011-06-22 00:20:26.130712767 +0200
+++ strace.6/process.c	2011-06-22 13:37:06.210864935 +0200
@@ -495,7 +495,6 @@ internal_fork(struct tcb *tcp)
 			return 0;
 		if (!followfork)
 			return 0;
-		tcp->flags |= TCB_FOLLOWFORK;
 		if (syserror(tcp))
 			return 0;
 		tcpchild = alloctcb(tcp->u_rval);
@@ -796,7 +795,6 @@ handle_new_child(struct tcb *tcp, int pi
 	else
 #endif /* CLONE_PTRACE */
 	{
-		tcp->flags |= TCB_FOLLOWFORK;
 		tcpchild = alloctcb(pid);
 	}
 
@@ -892,10 +890,10 @@ internal_fork(struct tcb *tcp)
 	   == (PTRACE_O_TRACECLONE | PTRACE_O_TRACEFORK | PTRACE_O_TRACEVFORK))
 		return 0;
 
+	if (!followfork)
+		return 0;
+
 	if (entering(tcp)) {
-		tcp->flags &= ~TCB_FOLLOWFORK;
-		if (!followfork)
-			return 0;
 		/*
 		 * In occasion of using PTRACE_O_TRACECLONE, we won't see the
 		 * new child if clone is called with flag CLONE_UNTRACED, so
@@ -904,15 +902,11 @@ internal_fork(struct tcb *tcp)
 		if ((sysent[tcp->scno].sys_func == sys_clone) &&
 		    (tcp->u_arg[ARG_FLAGS] & CLONE_UNTRACED))
 			return 0;
-		tcp->flags |= TCB_FOLLOWFORK;
 		setbpt(tcp);
 	} else {
 		int pid;
 		int bpt;
 
-		if (!(tcp->flags & TCB_FOLLOWFORK))
-			return 0;
-
 		bpt = tcp->flags & TCB_BPTSET;
 
 		if (syserror(tcp)) {
@@ -944,17 +938,18 @@ internal_fork(struct tcb *tcp)
 			dont_follow = 1;
 	}
 #endif
+
+	if (!followfork)
+		return 0;
+
 	if (entering(tcp)) {
-		if (!followfork || dont_follow)
+		if (dont_follow)
 			return 0;
-		tcp->flags |= TCB_FOLLOWFORK;
 		setbpt(tcp);
 	}
 	else {
 		int bpt = tcp->flags & TCB_BPTSET;
 
-		if (!(tcp->flags & TCB_FOLLOWFORK))
-			return 0;
 		if (bpt)
 			clearbpt(tcp);
 
@@ -962,7 +957,6 @@ internal_fork(struct tcb *tcp)
 			return 0;
 
 		pid = tcp->u_rval;
-		tcp->flags |= TCB_FOLLOWFORK;
 		tcpchild = alloctcb(pid);
 #ifdef SUNOS4
 #ifdef oldway
diff -d -urpN strace.5/strace.c strace.6/strace.c
--- strace.5/strace.c	2011-06-21 23:18:34.278875859 +0200
+++ strace.6/strace.c	2011-06-21 23:36:06.105405997 +0200
@@ -480,7 +480,7 @@ startup_attach(void)
 						++nerr;
 					else if (tid != tcbtab[tcbi]->pid) {
 						tcp = alloctcb(tid);
-						tcp->flags |= TCB_ATTACHED|TCB_CLONE_THREAD|TCB_FOLLOWFORK;
+						tcp->flags |= TCB_ATTACHED|TCB_CLONE_THREAD;
 						tcbtab[tcbi]->nclone_threads++;
 						tcp->parent = tcbtab[tcbi];
 					}