s390/runtime instrumentation: simplify task exit handling

BugLink: http://bugs.launchpad.net/bugs/1745046

commit 8d9047f8 upstream.

Free data structures required for runtime instrumentation from
arch_release_task_struct(). This allows to simplify the code a bit,
and also makes the semantics a bit easier: arch_release_task_struct()
is never called from the task that is being removed.

In addition this allows to get rid of exit_thread() in a later patch.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

arch/s390/include/asm/runtime_instr.h

@@ -85,6 +85,8 @@ static inline void restore_ri_cb(struct runtime_instr_cb *cb_next,
 		load_runtime_instr_cb(&runtime_instr_empty_cb);
 }
 
-void exit_thread_runtime_instr(void);
+struct task_struct;
+
+void runtime_instr_release(struct task_struct *tsk);
 
 #endif /* _RUNTIME_INSTR_H */

arch/s390/kernel/process.c

@@ -72,7 +72,6 @@ extern void kernel_thread_starter(void);
  */
 void exit_thread(void)
 {
-	exit_thread_runtime_instr();
 }
 
 void flush_thread(void)
@@ -87,6 +86,7 @@ void arch_release_task_struct(struct task_struct *tsk)
 {
 	/* Free either the floating-point or the vector register save area */
 	kfree(tsk->thread.fpu.regs);
+	runtime_instr_release(tsk);
 }
 
 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)

arch/s390/kernel/runtime_instr.c

@@ -18,11 +18,24 @@
 /* empty control block to disable RI by loading it */
 struct runtime_instr_cb runtime_instr_empty_cb;
 
+void runtime_instr_release(struct task_struct *tsk)
+{
+	kfree(tsk->thread.ri_cb);
+}
+
 static void disable_runtime_instr(void)
 {
-	struct pt_regs *regs = task_pt_regs(current);
+	struct task_struct *task = current;
+	struct pt_regs *regs;
 
+	if (!task->thread.ri_cb)
+		return;
+	regs = task_pt_regs(task);
+	preempt_disable();
 	load_runtime_instr_cb(&runtime_instr_empty_cb);
+	kfree(task->thread.ri_cb);
+	task->thread.ri_cb = NULL;
+	preempt_enable();
 
 	/*
 	 * Make sure the RI bit is deleted from the PSW. If the user did not
@@ -43,19 +56,6 @@ static void init_runtime_instr_cb(struct runtime_instr_cb *cb)
 	cb->valid = 1;
 }
 
-void exit_thread_runtime_instr(void)
-{
-	struct task_struct *task = current;
-
-	preempt_disable();
-	if (!task->thread.ri_cb)
-		return;
-	disable_runtime_instr();
-	kfree(task->thread.ri_cb);
-	task->thread.ri_cb = NULL;
-	preempt_enable();
-}
-
 SYSCALL_DEFINE1(s390_runtime_instr, int, command)
 {
 	struct runtime_instr_cb *cb;
@@ -64,7 +64,7 @@ SYSCALL_DEFINE1(s390_runtime_instr, int, command)
 		return -EOPNOTSUPP;
 
 	if (command == S390_RUNTIME_INSTR_STOP) {
-		exit_thread_runtime_instr();
+		disable_runtime_instr();
 		return 0;
 	}