1 files changed, 27 insertions, 18 deletions

diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 46ef3fd0663..72cec9ecd96 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -294,7 +294,7 @@ static inline int do_exception(struct pt_regs *regs, int access)
 	down_read(&mm->mmap_sem);
 
 #ifdef CONFIG_PGSTE
-	if (test_tsk_thread_flag(current, TIF_SIE) && S390_lowcore.gmap) {
+	if ((current->flags & PF_VCPU) && S390_lowcore.gmap) {
 		address = __gmap_fault(address,
 				     (struct gmap *) S390_lowcore.gmap);
 		if (address == -EFAULT) {
@@ -549,19 +549,15 @@ static void pfault_interrupt(struct ext_code ext_code,
 	if ((subcode & 0xff00) != __SUBCODE_MASK)
 		return;
 	kstat_cpu(smp_processor_id()).irqs[EXTINT_PFL]++;
-	if (subcode & 0x0080) {
-		/* Get the token (= pid of the affected task). */
-		pid = sizeof(void *) == 4 ? param32 : param64;
-		rcu_read_lock();
-		tsk = find_task_by_pid_ns(pid, &init_pid_ns);
-		if (tsk)
-			get_task_struct(tsk);
-		rcu_read_unlock();
-		if (!tsk)
-			return;
-	} else {
-		tsk = current;
-	}
+	/* Get the token (= pid of the affected task). */
+	pid = sizeof(void *) == 4 ? param32 : param64;
+	rcu_read_lock();
+	tsk = find_task_by_pid_ns(pid, &init_pid_ns);
+	if (tsk)
+		get_task_struct(tsk);
+	rcu_read_unlock();
+	if (!tsk)
+		return;
 	spin_lock(&pfault_lock);
 	if (subcode & 0x0080) {
 		/* signal bit is set -> a page has been swapped in by VM */
@@ -574,6 +570,7 @@ static void pfault_interrupt(struct ext_code ext_code,
 			tsk->thread.pfault_wait = 0;
 			list_del(&tsk->thread.list);
 			wake_up_process(tsk);
+			put_task_struct(tsk);
 		} else {
 			/* Completion interrupt was faster than initial
 			 * interrupt. Set pfault_wait to -1 so the initial
@@ -585,24 +582,35 @@ static void pfault_interrupt(struct ext_code ext_code,
 			if (tsk->state == TASK_RUNNING)
 				tsk->thread.pfault_wait = -1;
 		}
-		put_task_struct(tsk);
 	} else {
 		/* signal bit not set -> a real page is missing. */
-		if (tsk->thread.pfault_wait == -1) {
+		if (WARN_ON_ONCE(tsk != current))
+			goto out;
+		if (tsk->thread.pfault_wait == 1) {
+			/* Already on the list with a reference: put to sleep */
+			__set_task_state(tsk, TASK_UNINTERRUPTIBLE);
+			set_tsk_need_resched(tsk);
+		} else if (tsk->thread.pfault_wait == -1) {
 			/* Completion interrupt was faster than the initial
 			 * interrupt (pfault_wait == -1). Set pfault_wait
 			 * back to zero and exit. */
 			tsk->thread.pfault_wait = 0;
 		} else {
 			/* Initial interrupt arrived before completion
-			 * interrupt. Let the task sleep. */
+			 * interrupt. Let the task sleep.
+			 * An extra task reference is needed since a different
+			 * cpu may set the task state to TASK_RUNNING again
+			 * before the scheduler is reached. */
+			get_task_struct(tsk);
 			tsk->thread.pfault_wait = 1;
 			list_add(&tsk->thread.list, &pfault_list);
-			set_task_state(tsk, TASK_UNINTERRUPTIBLE);
+			__set_task_state(tsk, TASK_UNINTERRUPTIBLE);
 			set_tsk_need_resched(tsk);
 		}
 	}
+out:
 	spin_unlock(&pfault_lock);
+	put_task_struct(tsk);
 }
 
 static int __cpuinit pfault_cpu_notify(struct notifier_block *self,
@@ -620,6 +628,7 @@ static int __cpuinit pfault_cpu_notify(struct notifier_block *self,
 			list_del(&thread->list);
 			tsk = container_of(thread, struct task_struct, thread);
 			wake_up_process(tsk);
+			put_task_struct(tsk);
 		}
 		spin_unlock_irq(&pfault_lock);
 		break;