futex: Provide and use pi_state_update_owner()

Updating pi_state::owner is done at several places with the same
code. Provide a function for it and use that at the obvious places.

This is also a preparation for a bug fix to avoid yet another copy of the
same code or alternatively introducing a completely unpenetratable mess of
gotos.

Originally-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org

diff --git a/kernel/futex.c b/kernel/futex.c
index 5dc8f89..7837f9e 100644 (file)
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -763,6 +763,29 @@ static struct futex_pi_state *alloc_pi_state(void)
        return pi_state;
 }
 
+static void pi_state_update_owner(struct futex_pi_state *pi_state,
+                                 struct task_struct *new_owner)
+{
+       struct task_struct *old_owner = pi_state->owner;
+
+       lockdep_assert_held(&pi_state->pi_mutex.wait_lock);
+
+       if (old_owner) {
+               raw_spin_lock(&old_owner->pi_lock);
+               WARN_ON(list_empty(&pi_state->list));
+               list_del_init(&pi_state->list);
+               raw_spin_unlock(&old_owner->pi_lock);
+       }
+
+       if (new_owner) {
+               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);
+       }
+}
+
 static void get_pi_state(struct futex_pi_state *pi_state)
 {
        WARN_ON_ONCE(!refcount_inc_not_zero(&pi_state->refcount));
@@ -1521,26 +1544,15 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_pi_state *pi_
                        ret = -EINVAL;
        }
 
-       if (ret)
-               goto out_unlock;
-
-       /*
-        * This is a point of no return; once we modify the uval there is no
-        * going back and subsequent operations must not fail.
-        */
-
-       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);
-
-       postunlock = __rt_mutex_futex_unlock(&pi_state->pi_mutex, &wake_q);
+       if (!ret) {
+               /*
+                * This is a point of no return; once we modified the uval
+                * there is no going back and subsequent operations must
+                * not fail.
+                */
+               pi_state_update_owner(pi_state, new_owner);
+               postunlock = __rt_mutex_futex_unlock(&pi_state->pi_mutex, &wake_q);
+       }
 
 out_unlock:
        raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
@@ -2433,19 +2445,7 @@ retry:
         * We fixed up user space. Now we need to fix the pi_state
         * itself.
         */
-       if (pi_state->owner != NULL) {
-               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);
-       }
-
-       pi_state->owner = newowner;
-
-       raw_spin_lock(&newowner->pi_lock);
-       WARN_ON(!list_empty(&pi_state->list));
-       list_add(&pi_state->list, &newowner->pi_state_list);
-       raw_spin_unlock(&newowner->pi_lock);
+       pi_state_update_owner(pi_state, newowner);
        raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
 
        return argowner == current;