lowmemorykiller: maintain LMK rbtree with signal->adj_node

Currently, we maintain LMK rbtree with task->adj_node. However, when
handling oom_score_adj change case, we may del/add a non-leader task
to the RB tree, which is not as expected.

This patch we maintain the LMK rbtree with task->signal->adj_node.
Since signal_struct is shared between main task and threads, we can
avoid non-leader thread adding to tree.

Change-Id: I3ba9e740e03ab04c25497a1cc2c870f051bd5b07
Signed-off-by: Hong-Mei Li <a21834@motorola.com>
Reviewed-on: http://gerrit.mot.com/754225
SME-Granted: SME Approvals Granted
SLTApproved: Slta Waiver <sltawvr@motorola.com>
Tested-by: Jira Key <jirakey@motorola.com>
Reviewed-by: Zhi-Ming Yuan <a14194@motorola.com>
Reviewed-by: Yi-Wei Zhao <gbjc64@motorola.com>
Submit-Approved: Jira Key <jirakey@motorola.com>
(cherry picked from commit b40634023f9152c6232de9acb80108e0af7e4075)
Signed-off-by: Abdul Salam <salamab@motorola.com>
Reviewed-on: http://gerrit.mot.com/766107
Reviewed-by: Sudharsan Yettapu <sudharsan.yettapu@motorola.com>
Reviewed-by: Ravikumar Vembu <raviv@motorola.com>
(cherry picked from commit f3abd37ce3b4d36ae05cfc1c5cd10e5a3f584e7f)
Reviewed-on: http://gerrit.mot.com/768302

1 files changed, 24 insertions, 12 deletions

diff --git a/drivers/staging/android/lowmemorykiller.c b/drivers/staging/android/lowmemorykiller.c
index c6ee61ca4a6..f68459a36db 100644
--- a/drivers/staging/android/lowmemorykiller.c
+++ b/drivers/staging/android/lowmemorykiller.c
@@ -420,11 +420,14 @@ static const struct kparam_array __param_arr_adj = {
 #ifdef CONFIG_ANDROID_LMK_ADJ_RBTREE
 DEFINE_SPINLOCK(lmk_lock);
 struct rb_root tasks_scoreadj = RB_ROOT;
+/*
+ * Makesure to invoke the function with holding sighand->siglock
+ */
 void add_2_adj_tree(struct task_struct *task)
 {
 	struct rb_node **link;
 	struct rb_node *parent = NULL;
-	struct task_struct *task_entry;
+	struct signal_struct *sig_entry;
 	s64 key = task->signal->oom_score_adj;
 
 	/*
@@ -434,25 +437,28 @@ void add_2_adj_tree(struct task_struct *task)
 	link =  &tasks_scoreadj.rb_node;
 	while (*link) {
 		parent = *link;
-		task_entry = rb_entry(parent, struct task_struct, adj_node);
+		sig_entry = rb_entry(parent, struct signal_struct, adj_node);
 
-		if (key < task_entry->signal->oom_score_adj)
+		if (key < sig_entry->oom_score_adj)
 			link = &parent->rb_right;
 		else
 			link = &parent->rb_left;
 	}
 
-	rb_link_node(&task->adj_node, parent, link);
-	rb_insert_color(&task->adj_node, &tasks_scoreadj);
+	rb_link_node(&task->signal->adj_node, parent, link);
+	rb_insert_color(&task->signal->adj_node, &tasks_scoreadj);
 	spin_unlock(&lmk_lock);
 }
 
+/*
+ * Makesure to invoke the function with holding sighand->siglock
+ */
 void delete_from_adj_tree(struct task_struct *task)
 {
 	spin_lock(&lmk_lock);
-	if (!RB_EMPTY_NODE(&task->adj_node)) {
-		rb_erase(&task->adj_node, &tasks_scoreadj);
-		RB_CLEAR_NODE(&task->adj_node);
+	if (!RB_EMPTY_NODE(&task->signal->adj_node)) {
+		rb_erase(&task->signal->adj_node, &tasks_scoreadj);
+		RB_CLEAR_NODE(&task->signal->adj_node);
 	}
 	spin_unlock(&lmk_lock);
 }
@@ -461,20 +467,23 @@ void delete_from_adj_tree(struct task_struct *task)
 static struct task_struct *pick_next_from_adj_tree(struct task_struct *task)
 {
 	struct rb_node *next;
+	struct signal_struct *next_tsk_sig;
 
 	spin_lock(&lmk_lock);
-	next = rb_next(&task->adj_node);
+	next = rb_next(&task->signal->adj_node);
 	spin_unlock(&lmk_lock);
 
 	if (!next)
 		return NULL;
 
-	 return rb_entry(next, struct task_struct, adj_node);
+	next_tsk_sig = rb_entry(next, struct signal_struct, adj_node);
+	return next_tsk_sig->curr_target->group_leader;
 }
 
 static struct task_struct *pick_first_task(void)
 {
 	struct rb_node *left;
+	struct signal_struct *first_tsk_sig;
 
 	spin_lock(&lmk_lock);
 	left = rb_first(&tasks_scoreadj);
@@ -483,12 +492,14 @@ static struct task_struct *pick_first_task(void)
 	if (!left)
 		return NULL;
 
-	return rb_entry(left, struct task_struct, adj_node);
+	first_tsk_sig = rb_entry(left, struct signal_struct, adj_node);
+	return first_tsk_sig->curr_target->group_leader;
 }
 
 static struct task_struct *pick_last_task(void)
 {
 	struct rb_node *right;
+	struct signal_struct *last_tsk_sig;
 
 	spin_lock(&lmk_lock);
 	right = rb_last(&tasks_scoreadj);
@@ -497,7 +508,8 @@ static struct task_struct *pick_last_task(void)
 	if (!right)
 		return NULL;
 
-	return rb_entry(right, struct task_struct, adj_node);
+	last_tsk_sig = rb_entry(right, struct signal_struct, adj_node);
+	return last_tsk_sig->curr_target->group_leader;
 }
 #endif