===== arch/i386/kernel/ptrace.c 1.28 vs edited =====
--- 1.28/arch/i386/kernel/ptrace.c	2004-11-22 09:44:52 -08:00
+++ edited/arch/i386/kernel/ptrace.c	2004-12-29 16:42:04 -08:00
@@ -142,18 +142,31 @@
 {
 	long eflags;
 
+	/*
+	 * Always set TIF_SINGLESTEP - this guarantees that 
+	 * we single-step system calls etc.. 
+	 */
 	set_tsk_thread_flag(child, TIF_SINGLESTEP);
+
+	/*
+	 * If TF was already set, don't do anything else
+	 */
 	eflags = get_stack_long(child, EFL_OFFSET);
+	if (flags & TRAP_FLAG)
+		return;
 	put_stack_long(child, EFL_OFFSET, eflags | TRAP_FLAG);
 	child->ptrace |= PT_DTRACE;
 }
 
 static void clear_singlestep(struct task_struct *child)
 {
+	/* Always clear TIF_SINGLESTEP... */
+	clear_tsk_thread_flag(child, TIF_SINGLESTEP);
+
+	/* But touch TF only if it was set by us.. */
 	if (child->ptrace & PT_DTRACE) {
 		long eflags;
 
-		clear_tsk_thread_flag(child, TIF_SINGLESTEP);
 		eflags = get_stack_long(child, EFL_OFFSET);
 		put_stack_long(child, EFL_OFFSET, eflags & ~TRAP_FLAG);
 		child->ptrace &= ~PT_DTRACE;