linux-kernel - [PATCH v4 04/20] futex: Consolidate pure pi_state

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Date:   Thu, 29 Dec 2016 11:13:30 -0500
From:   Waiman Long <longman@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Jonathan Corbet <corbet@....net>
Cc:     linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        Mike Galbraith <umgwanakikbuti@...il.com>,
        Scott J Norton <scott.norton@....com>,
        Waiman Long <longman@...hat.com>
Subject: [PATCH v4 04/20] futex: Consolidate pure pi_state_list add & delete codes to helpers

Two new helper functions (task_pi_list_add & task_pi_list_del)
are created to consolidate all the pure pi_state_list addition and
insertion codes. The set_owner argument in task_pi_list_add() will
be needed in a later patch.

Signed-off-by: Waiman Long <longman@...hat.com>
---
 kernel/futex.c | 64 +++++++++++++++++++++++++++++++++++-----------------------
 1 file changed, 39 insertions(+), 25 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index 7590c7d..ccec962 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -822,6 +822,39 @@ static inline int get_futex_value(u32 *dest, u32 __user *from)
 /*
  * PI code:
  */
+
+/**
+ * task_pi_list_add - add futex state object to a task's pi_state_list
+ * @task : task structure
+ * @state: futex state object
+ */
+static inline void task_pi_list_add(struct task_struct *task,
+				    struct futex_state *state)
+{
+	raw_spin_lock_irq(&task->pi_lock);
+	WARN_ON(!list_empty(&state->list));
+	list_add(&state->list, &task->pi_state_list);
+	state->owner = task;
+	raw_spin_unlock_irq(&task->pi_lock);
+}
+
+/**
+ * task_pi_list_del - delete futex state object from a task's pi_state_list
+ * @state: futex state object
+ * @warn : warn if list is empty when set
+ */
+static inline void task_pi_list_del(struct futex_state *state, const bool warn)
+{
+	struct task_struct *task = state->owner;
+
+	raw_spin_lock_irq(&task->pi_lock);
+	if (warn)
+		WARN_ON(list_empty(&state->list));
+	list_del_init(&state->list);
+	state->owner = NULL;
+	raw_spin_unlock_irq(&task->pi_lock);
+}
+
 static int refill_futex_state_cache(void)
 {
 	struct futex_state *state;
@@ -874,9 +907,7 @@ static void put_futex_state(struct futex_state *state)
 	 * and has cleaned up the futex state already
 	 */
 	if (state->owner) {
-		raw_spin_lock_irq(&state->owner->pi_lock);
-		list_del_init(&state->list);
-		raw_spin_unlock_irq(&state->owner->pi_lock);
+		task_pi_list_del(state, false);
 
 		rt_mutex_proxy_unlock(&state->pi_mutex, state->owner);
 	}
@@ -1397,16 +1428,8 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this,
 		return ret;
 	}
 
-	raw_spin_lock(&pi_state->owner->pi_lock);
-	WARN_ON(list_empty(&pi_state->list));
-	list_del_init(&pi_state->list);
-	raw_spin_unlock(&pi_state->owner->pi_lock);
-
-	raw_spin_lock(&new_owner->pi_lock);
-	WARN_ON(!list_empty(&pi_state->list));
-	list_add(&pi_state->list, &new_owner->pi_state_list);
-	pi_state->owner = new_owner;
-	raw_spin_unlock(&new_owner->pi_lock);
+	task_pi_list_del(pi_state, true);
+	task_pi_list_add(new_owner, pi_state);
 
 	raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
 
@@ -2211,19 +2234,10 @@ static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
 	 * We fixed up user space. Now we need to fix the pi_state
 	 * itself.
 	 */
-	if (pi_state->owner != NULL) {
-		raw_spin_lock_irq(&pi_state->owner->pi_lock);
-		WARN_ON(list_empty(&pi_state->list));
-		list_del_init(&pi_state->list);
-		raw_spin_unlock_irq(&pi_state->owner->pi_lock);
-	}
+	if (pi_state->owner != NULL)
+		task_pi_list_del(pi_state, true);
 
-	pi_state->owner = newowner;
-
-	raw_spin_lock_irq(&newowner->pi_lock);
-	WARN_ON(!list_empty(&pi_state->list));
-	list_add(&pi_state->list, &newowner->pi_state_list);
-	raw_spin_unlock_irq(&newowner->pi_lock);
+	task_pi_list_add(newowner, pi_state);
 	return 0;
 
 	/*
-- 
1.8.3.1