From 6f6c955aa53337c1979eefeae185c14e9dda5fe0 Mon Sep 17 00:00:00 2001
From: Thierry Strudel <tstrudel@google.com>
Date: Tue, 22 Dec 2015 10:13:14 -0800
Subject: [PATCH] Revert "android/lowmemorykiller: Ignore tasks with freed mm"

This reverts commit 05d5ad4d0af90e05d63da7945282c7f5dc18f682.

Change-Id: Ib5770b5b38f123116322507646ae9bce6c3c186a
---
 arch/arm/include/asm/thread_info.h        |  2 +-
 drivers/staging/android/lowmemorykiller.c | 10 ++--------
 include/linux/sched.h                     |  2 +-
 kernel/exit.c                             |  6 +-----
 kernel/fork.c                             |  5 +----
 5 files changed, 6 insertions(+), 19 deletions(-)

diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index 100773a78179..b15392e5c0d7 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -161,7 +161,7 @@ extern int vfp_restore_user_hwstate(struct user_vfp __user *,
 #define TIF_USING_IWMMXT	17
 #define TIF_MEMDIE		18	/* is terminating due to OOM killer */
 #define TIF_RESTORE_SIGMASK	20
-#define TIF_MM_RELEASED		23	/* task MM has been released */
+#define TIF_SWITCH_MM		22	/* deferred switch_mm */
 
 #define _TIF_SIGPENDING		(1 << TIF_SIGPENDING)
 #define _TIF_NEED_RESCHED	(1 << TIF_NEED_RESCHED)
diff --git a/drivers/staging/android/lowmemorykiller.c b/drivers/staging/android/lowmemorykiller.c
index c39d563da06d..d4775b5cc999 100644
--- a/drivers/staging/android/lowmemorykiller.c
+++ b/drivers/staging/android/lowmemorykiller.c
@@ -151,10 +151,6 @@ static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
 		if (tsk->flags & PF_KTHREAD)
 			continue;
 
-		/* if task no longer has any memory ignore it */
-		if (test_task_flag(tsk, TIF_MM_RELEASED))
-			continue;
-
 		if (time_before_eq(jiffies, lowmem_deathpending_timeout)) {
 			if (test_task_flag(tsk, TIF_MEMDIE)) {
 				rcu_read_unlock();
@@ -212,14 +208,12 @@ static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
 		set_tsk_thread_flag(selected, TIF_MEMDIE);
 		send_sig(SIGKILL, selected, 0);
 		rem -= selected_tasksize;
-		rcu_read_unlock();
 		/* give the system time to free up the memory */
 		msleep_interruptible(20);
-	} else
-		rcu_read_unlock();
-
+	}
 	lowmem_print(4, "lowmem_shrink %lu, %x, return %d\n",
 		     nr_to_scan, sc->gfp_mask, rem);
+	rcu_read_unlock();
 	mutex_unlock(&scan_mutex);
 	return rem;
 }
diff --git a/include/linux/sched.h b/include/linux/sched.h
index e145e7e98bfb..eeb1c821c2f0 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2411,7 +2411,7 @@ static inline void mmdrop(struct mm_struct * mm)
 }
 
 /* mmput gets rid of the mappings and all user-space */
-extern int mmput(struct mm_struct *);
+extern void mmput(struct mm_struct *);
 /* Grab a reference to a task's mm, if it is not already going away */
 extern struct mm_struct *get_task_mm(struct task_struct *task);
 /*
diff --git a/kernel/exit.c b/kernel/exit.c
index 4767d4fc1afb..4ca44ff50260 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -409,7 +409,6 @@ static void exit_mm(struct task_struct * tsk)
 {
 	struct mm_struct *mm = tsk->mm;
 	struct core_state *core_state;
-	int mm_released;
 
 	mm_release(tsk, mm);
 	if (!mm)
@@ -455,10 +454,7 @@ static void exit_mm(struct task_struct * tsk)
 	enter_lazy_tlb(mm, current);
 	task_unlock(tsk);
 	mm_update_next_owner(mm);
-
-	mm_released = mmput(mm);
-	if (mm_released)
-		set_tsk_thread_flag(tsk, TIF_MM_RELEASED);
+	mmput(mm);
 }
 
 /*
diff --git a/kernel/fork.c b/kernel/fork.c
index cad09317184b..5772298ebef1 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -630,9 +630,8 @@ EXPORT_SYMBOL_GPL(__mmdrop);
 /*
  * Decrement the use count and release all resources for an mm.
  */
-int mmput(struct mm_struct *mm)
+void mmput(struct mm_struct *mm)
 {
-	int mm_freed = 0;
 	might_sleep();
 
 	if (atomic_dec_and_test(&mm->mm_users)) {
@@ -650,9 +649,7 @@ int mmput(struct mm_struct *mm)
 		if (mm->binfmt)
 			module_put(mm->binfmt->module);
 		mmdrop(mm);
-		mm_freed = 1;
 	}
-	return mm_freed;
 }
 EXPORT_SYMBOL_GPL(mmput);