From: Heiko Carstens <heiko.carstens@de.ibm.com>
Date: Mon, 11 Sep 2017 11:24:23 +0200
Subject: s390/guarded storage: simplify task exit handling
Git-commit: 7b83c6297d2fc7350997e86188df84c27fd59530
Patch-mainline: v4.15-rc1
References: bsc#1203254 LTC#199911

Free data structures required for guarded storage 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>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 arch/s390/include/asm/processor.h  |    4 ++--
 arch/s390/kernel/guarded_storage.c |    9 +++------
 arch/s390/kernel/process.c         |    3 +--
 3 files changed, 6 insertions(+), 10 deletions(-)

--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -220,8 +220,8 @@ void show_cacheinfo(struct seq_file *m);
 /* Free all resources held by a thread. */
 extern void release_thread(struct task_struct *);
 
-/* Free guarded storage control block for current */
-void exit_thread_gs(void);
+/* Free guarded storage control block */
+void guarded_storage_release(struct task_struct *tsk);
 
 unsigned long get_wchan(struct task_struct *p);
 #define task_pt_regs(tsk) ((struct pt_regs *) \
--- a/arch/s390/kernel/guarded_storage.c
+++ b/arch/s390/kernel/guarded_storage.c
@@ -11,13 +11,10 @@
 #include <asm/guarded_storage.h>
 #include "entry.h"
 
-void exit_thread_gs(void)
+void guarded_storage_release(struct task_struct *tsk)
 {
-	preempt_disable();
-	kfree(current->thread.gs_cb);
-	kfree(current->thread.gs_bc_cb);
-	current->thread.gs_cb = current->thread.gs_bc_cb = NULL;
-	preempt_enable();
+	kfree(tsk->thread.gs_cb);
+	kfree(tsk->thread.gs_bc_cb);
 }
 
 static int gs_enable(void)
--- a/arch/s390/kernel/process.c
+++ b/arch/s390/kernel/process.c
@@ -48,8 +48,6 @@ extern void kernel_thread_starter(void);
  */
 void exit_thread(struct task_struct *tsk)
 {
-	if (tsk == current)
-		exit_thread_gs();
 }
 
 void flush_thread(void)
@@ -63,6 +61,7 @@ void release_thread(struct task_struct *
 void arch_release_task_struct(struct task_struct *tsk)
 {
 	runtime_instr_release(tsk);
+	guarded_storage_release(tsk);
 }
 
 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)