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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-09-08 01:01:14 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-09-08 01:01:14 -0300
commite5fd91f1ef340da553f7a79da9540c3db711c937 (patch)
treeb11842027dc6641da63f4bcc524f8678263304a3 /kernel/futex.c
parent2a9b0348e685a63d97486f6749622b61e9e3292f (diff)
Linux-libre 4.2-gnu
Diffstat (limited to 'kernel/futex.c')
-rw-r--r--kernel/futex.c72
1 files changed, 48 insertions, 24 deletions
diff --git a/kernel/futex.c b/kernel/futex.c
index 2579e407f..c4a182f53 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1090,9 +1090,11 @@ static void __unqueue_futex(struct futex_q *q)
/*
* The hash bucket lock must be held when this is called.
- * Afterwards, the futex_q must not be accessed.
+ * Afterwards, the futex_q must not be accessed. Callers
+ * must ensure to later call wake_up_q() for the actual
+ * wakeups to occur.
*/
-static void wake_futex(struct futex_q *q)
+static void mark_wake_futex(struct wake_q_head *wake_q, struct futex_q *q)
{
struct task_struct *p = q->task;
@@ -1100,14 +1102,10 @@ static void wake_futex(struct futex_q *q)
return;
/*
- * We set q->lock_ptr = NULL _before_ we wake up the task. If
- * a non-futex wake up happens on another CPU then the task
- * might exit and p would dereference a non-existing task
- * struct. Prevent this by holding a reference on p across the
- * wake up.
+ * Queue the task for later wakeup for after we've released
+ * the hb->lock. wake_q_add() grabs reference to p.
*/
- get_task_struct(p);
-
+ wake_q_add(wake_q, p);
__unqueue_futex(q);
/*
* The waiting task can free the futex_q as soon as
@@ -1117,16 +1115,16 @@ static void wake_futex(struct futex_q *q)
*/
smp_wmb();
q->lock_ptr = NULL;
-
- wake_up_state(p, TASK_NORMAL);
- put_task_struct(p);
}
-static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
+static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this,
+ struct futex_hash_bucket *hb)
{
struct task_struct *new_owner;
struct futex_pi_state *pi_state = this->pi_state;
u32 uninitialized_var(curval), newval;
+ WAKE_Q(wake_q);
+ bool deboost;
int ret = 0;
if (!pi_state)
@@ -1178,7 +1176,19 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
raw_spin_unlock_irq(&new_owner->pi_lock);
raw_spin_unlock(&pi_state->pi_mutex.wait_lock);
- rt_mutex_unlock(&pi_state->pi_mutex);
+
+ deboost = rt_mutex_futex_unlock(&pi_state->pi_mutex, &wake_q);
+
+ /*
+ * First unlock HB so the waiter does not spin on it once he got woken
+ * up. Second wake up the waiter before the priority is adjusted. If we
+ * deboost first (and lose our higher priority), then the task might get
+ * scheduled away before the wake up can take place.
+ */
+ spin_unlock(&hb->lock);
+ wake_up_q(&wake_q);
+ if (deboost)
+ rt_mutex_adjust_prio(current);
return 0;
}
@@ -1217,6 +1227,7 @@ futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset)
struct futex_q *this, *next;
union futex_key key = FUTEX_KEY_INIT;
int ret;
+ WAKE_Q(wake_q);
if (!bitset)
return -EINVAL;
@@ -1244,13 +1255,14 @@ futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset)
if (!(this->bitset & bitset))
continue;
- wake_futex(this);
+ mark_wake_futex(&wake_q, this);
if (++ret >= nr_wake)
break;
}
}
spin_unlock(&hb->lock);
+ wake_up_q(&wake_q);
out_put_key:
put_futex_key(&key);
out:
@@ -1269,6 +1281,7 @@ futex_wake_op(u32 __user *uaddr1, unsigned int flags, u32 __user *uaddr2,
struct futex_hash_bucket *hb1, *hb2;
struct futex_q *this, *next;
int ret, op_ret;
+ WAKE_Q(wake_q);
retry:
ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, VERIFY_READ);
@@ -1320,7 +1333,7 @@ retry_private:
ret = -EINVAL;
goto out_unlock;
}
- wake_futex(this);
+ mark_wake_futex(&wake_q, this);
if (++ret >= nr_wake)
break;
}
@@ -1334,7 +1347,7 @@ retry_private:
ret = -EINVAL;
goto out_unlock;
}
- wake_futex(this);
+ mark_wake_futex(&wake_q, this);
if (++op_ret >= nr_wake2)
break;
}
@@ -1344,6 +1357,7 @@ retry_private:
out_unlock:
double_unlock_hb(hb1, hb2);
+ wake_up_q(&wake_q);
out_put_keys:
put_futex_key(&key2);
out_put_key1:
@@ -1503,6 +1517,7 @@ static int futex_requeue(u32 __user *uaddr1, unsigned int flags,
struct futex_pi_state *pi_state = NULL;
struct futex_hash_bucket *hb1, *hb2;
struct futex_q *this, *next;
+ WAKE_Q(wake_q);
if (requeue_pi) {
/*
@@ -1679,7 +1694,7 @@ retry_private:
* woken by futex_unlock_pi().
*/
if (++task_count <= nr_wake && !requeue_pi) {
- wake_futex(this);
+ mark_wake_futex(&wake_q, this);
continue;
}
@@ -1719,6 +1734,7 @@ retry_private:
out_unlock:
free_pi_state(pi_state);
double_unlock_hb(hb1, hb2);
+ wake_up_q(&wake_q);
hb_waiters_dec(hb2);
/*
@@ -2055,7 +2071,7 @@ static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q,
{
/*
* The task state is guaranteed to be set before another task can
- * wake it. set_current_state() is implemented using set_mb() and
+ * wake it. set_current_state() is implemented using smp_store_mb() and
* queue_me() calls spin_unlock() upon completion, both serializing
* access to the hash list and forcing another memory barrier.
*/
@@ -2063,11 +2079,8 @@ static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q,
queue_me(q, hb);
/* Arm the timer */
- if (timeout) {
+ if (timeout)
hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS);
- if (!hrtimer_active(&timeout->timer))
- timeout->task = NULL;
- }
/*
* If we have been removed from the hash list, then another task
@@ -2412,13 +2425,23 @@ retry:
*/
match = futex_top_waiter(hb, &key);
if (match) {
- ret = wake_futex_pi(uaddr, uval, match);
+ ret = wake_futex_pi(uaddr, uval, match, hb);
+ /*
+ * In case of success wake_futex_pi dropped the hash
+ * bucket lock.
+ */
+ if (!ret)
+ goto out_putkey;
/*
* The atomic access to the futex value generated a
* pagefault, so retry the user-access and the wakeup:
*/
if (ret == -EFAULT)
goto pi_faulted;
+ /*
+ * wake_futex_pi has detected invalid state. Tell user
+ * space.
+ */
goto out_unlock;
}
@@ -2439,6 +2462,7 @@ retry:
out_unlock:
spin_unlock(&hb->lock);
+out_putkey:
put_futex_key(&key);
return ret;