diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 03dc39f9..1795eb5f 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -965,7 +965,7 @@ void ptrace_report_signal(struct thread *thread, int sig)
 	proc->status = PS_TRACED;
 #endif /* POSTK_DEBUG_TEMP_FIX_41 */
 	thread->status = PS_TRACED;
-	proc->ptrace &= ~PT_TRACE_SYSCALL_MASK;
+	proc->ptrace &= ~PT_TRACE_SYSCALL;
 	if (sig == SIGSTOP || sig == SIGTSTP ||
 			sig == SIGTTIN || sig == SIGTTOU) {
 		proc->signal_flags |= SIGNAL_STOP_STOPPED;
diff --git a/arch/x86/kernel/syscall.c b/arch/x86/kernel/syscall.c
index aa4d8e52..f36a681e 100644
--- a/arch/x86/kernel/syscall.c
+++ b/arch/x86/kernel/syscall.c
@@ -537,7 +537,7 @@ void ptrace_report_signal(struct thread *thread, int sig)
 	/* Transition thread state */
 	proc->status = PS_TRACED;
 	thread->status = PS_TRACED;
-	proc->ptrace &= ~PT_TRACE_SYSCALL_MASK;
+	proc->ptrace &= ~PT_TRACE_SYSCALL;
 	if (sig == SIGSTOP || sig == SIGTSTP ||
 			sig == SIGTTIN || sig == SIGTTOU) {
 		proc->signal_flags |= SIGNAL_STOP_STOPPED;
diff --git a/kernel/include/process.h b/kernel/include/process.h
index 349827ed..445031ce 100644
--- a/kernel/include/process.h
+++ b/kernel/include/process.h
@@ -78,9 +78,7 @@
 // struct process.ptrace
 #define PT_TRACED 0x80     /* The process is ptraced */
 #define PT_TRACE_EXEC 0x100 /* Trace execve(2) */
-#define PT_TRACE_SYSCALL_ENTER 0x200 /* Trace syscall enter */
-#define PT_TRACE_SYSCALL_EXIT  0x400 /* Trace syscall exit */
-#define PT_TRACE_SYSCALL_MASK  (PT_TRACE_SYSCALL_ENTER | PT_TRACE_SYSCALL_EXIT)
+#define PT_TRACE_SYSCALL 0x200 /* Trace syscall enter */
 
 // ptrace(2) request
 #define	PTRACE_TRACEME 0
diff --git a/kernel/syscall.c b/kernel/syscall.c
index 489229f3..4a7dcd9a 100644
--- a/kernel/syscall.c
+++ b/kernel/syscall.c
@@ -2005,28 +2005,11 @@ static int ptrace_report_exec(struct thread *thread)
 	return 0;
 }
 
-
-static void ptrace_syscall_enter(struct thread *thread)
-{
-	int ptrace = thread->proc->ptrace;
-	struct mcs_rwlock_node_irqsave lock;
-
-	if (ptrace & PT_TRACE_SYSCALL_ENTER) {
-		int sig = (SIGTRAP | ((ptrace & PTRACE_O_TRACESYSGOOD) ? 0x80 : 0));
-		ptrace_report_signal(thread, sig);
-		mcs_rwlock_writer_lock(&thread->proc->update_lock, &lock);
-		if (thread->proc->ptrace & PT_TRACE_SYSCALL_ENTER) {
-			thread->proc->ptrace |= PT_TRACE_SYSCALL_EXIT;
-		}
-		mcs_rwlock_writer_unlock(&thread->proc->update_lock, &lock);
-	}
-}
-
-static void ptrace_syscall_exit(struct thread *thread)
+static void ptrace_syscall_event(struct thread *thread)
 {
 	int ptrace = thread->proc->ptrace;
 
-	if (ptrace & PT_TRACE_SYSCALL_EXIT) {
+	if (ptrace & PT_TRACE_SYSCALL) {
 		int sig = (SIGTRAP | ((ptrace & PTRACE_O_TRACESYSGOOD) ? 0x80 : 0));
 		ptrace_report_signal(thread, sig);
 	}
@@ -2076,7 +2059,7 @@ static int ptrace_report_clone(struct thread *thread, struct thread *new, int ev
 	thread->proc->status = PS_TRACED;
 	thread->status = PS_TRACED;
 	thread->proc->ptrace_eventmsg = new->tid;
-	thread->proc->ptrace &= ~PT_TRACE_SYSCALL_MASK;
+	thread->proc->ptrace &= ~PT_TRACE_SYSCALL; /** ??? **/
 	parent_pid = thread->proc->parent->pid;
 	mcs_rwlock_writer_unlock_noirq(&thread->proc->update_lock, &lock);
 
@@ -2275,7 +2258,7 @@ SYSCALL_DECLARE(execve)
 
 	if (cpu_local_var(current)->proc->ptrace) {
 		ihk_mc_syscall_ret(ctx) = 0;
-		ptrace_syscall_exit(cpu_local_var(current));
+		ptrace_syscall_event(cpu_local_var(current));
 	}
 
 	/* Unmap all memory areas of the process, userspace will be gone */
@@ -5682,9 +5665,9 @@ static int ptrace_wakeup_sig(int pid, long request, long data) {
 			set_single_step(child);
 		}
 		mcs_rwlock_writer_lock(&child->proc->update_lock, &lock);
-		child->proc->ptrace &= ~PT_TRACE_SYSCALL_MASK;
+		child->proc->ptrace &= ~PT_TRACE_SYSCALL;
 		if (request == PTRACE_SYSCALL) {
-			child->proc->ptrace |= PT_TRACE_SYSCALL_ENTER;
+			child->proc->ptrace |= PT_TRACE_SYSCALL;
 		}
 		mcs_rwlock_writer_unlock(&child->proc->update_lock, &lock);
 		if(data != 0 && data != SIGSTOP) {
@@ -9985,7 +9968,7 @@ long syscall(int num, ihk_mc_user_context_t *ctx)
 
 	if (cpu_local_var(current)->proc->ptrace) {
 		ihk_mc_syscall_ret(ctx) = -ENOSYS;
-		ptrace_syscall_enter(cpu_local_var(current));
+		ptrace_syscall_event(cpu_local_var(current));
 		num = ihk_mc_syscall_number(ctx);
 	}
 
@@ -10032,7 +10015,7 @@ long syscall(int num, ihk_mc_user_context_t *ctx)
 
 	if (cpu_local_var(current)->proc->ptrace && l != -ENOSYS) {
 		ihk_mc_syscall_ret(ctx) = l;
-		ptrace_syscall_exit(cpu_local_var(current));
+		ptrace_syscall_event(cpu_local_var(current));
 		l = ihk_mc_syscall_ret(ctx);
 	}