return prio;
}
+/*
+ * Update the waiter->tree copy of the sort keys.
+ */
static __always_inline void
waiter_update_prio(struct rt_mutex_waiter *waiter, struct task_struct *task)
{
- waiter->prio = __waiter_prio(task);
- waiter->deadline = task->dl.deadline;
+ lockdep_assert_held(&waiter->lock->wait_lock);
+ lockdep_assert(RB_EMPTY_NODE(&waiter->tree.entry));
+
+ waiter->tree.prio = __waiter_prio(task);
+ waiter->tree.deadline = task->dl.deadline;
+}
+
+/*
+ * Update the waiter->pi_tree copy of the sort keys (from the tree copy).
+ */
+static __always_inline void
+waiter_clone_prio(struct rt_mutex_waiter *waiter, struct task_struct *task)
+{
+ lockdep_assert_held(&waiter->lock->wait_lock);
+ lockdep_assert_held(&task->pi_lock);
+ lockdep_assert(RB_EMPTY_NODE(&waiter->pi_tree.entry));
+
+ waiter->pi_tree.prio = waiter->tree.prio;
+ waiter->pi_tree.deadline = waiter->tree.deadline;
}
/*
- * Only use with rt_mutex_waiter_{less,equal}()
+ * Only use with rt_waiter_node_{less,equal}()
*/
+#define task_to_waiter_node(p) \
+ &(struct rt_waiter_node){ .prio = __waiter_prio(p), .deadline = (p)->dl.deadline }
#define task_to_waiter(p) \
- &(struct rt_mutex_waiter){ .prio = __waiter_prio(p), .deadline = (p)->dl.deadline }
+ &(struct rt_mutex_waiter){ .tree = *task_to_waiter_node(p) }
-static __always_inline int rt_mutex_waiter_less(struct rt_mutex_waiter *left,
- struct rt_mutex_waiter *right)
+static __always_inline int rt_waiter_node_less(struct rt_waiter_node *left,
+ struct rt_waiter_node *right)
{
if (left->prio < right->prio)
return 1;
return 0;
}
-static __always_inline int rt_mutex_waiter_equal(struct rt_mutex_waiter *left,
- struct rt_mutex_waiter *right)
+static __always_inline int rt_waiter_node_equal(struct rt_waiter_node *left,
+ struct rt_waiter_node *right)
{
if (left->prio != right->prio)
return 0;
static inline bool rt_mutex_steal(struct rt_mutex_waiter *waiter,
struct rt_mutex_waiter *top_waiter)
{
- if (rt_mutex_waiter_less(waiter, top_waiter))
+ if (rt_waiter_node_less(&waiter->tree, &top_waiter->tree))
return true;
#ifdef RT_MUTEX_BUILD_SPINLOCKS
* Note that RT tasks are excluded from same priority (lateral)
* steals to prevent the introduction of an unbounded latency.
*/
- if (rt_prio(waiter->prio) || dl_prio(waiter->prio))
+ if (rt_prio(waiter->tree.prio) || dl_prio(waiter->tree.prio))
return false;
- return rt_mutex_waiter_equal(waiter, top_waiter);
+ return rt_waiter_node_equal(&waiter->tree, &top_waiter->tree);
#else
return false;
#endif
}
#define __node_2_waiter(node) \
- rb_entry((node), struct rt_mutex_waiter, tree_entry)
+ rb_entry((node), struct rt_mutex_waiter, tree.entry)
static __always_inline bool __waiter_less(struct rb_node *a, const struct rb_node *b)
{
struct rt_mutex_waiter *aw = __node_2_waiter(a);
struct rt_mutex_waiter *bw = __node_2_waiter(b);
- if (rt_mutex_waiter_less(aw, bw))
+ if (rt_waiter_node_less(&aw->tree, &bw->tree))
return 1;
if (!build_ww_mutex())
return 0;
- if (rt_mutex_waiter_less(bw, aw))
+ if (rt_waiter_node_less(&bw->tree, &aw->tree))
return 0;
/* NOTE: relies on waiter->ww_ctx being set before insertion */
static __always_inline void
rt_mutex_enqueue(struct rt_mutex_base *lock, struct rt_mutex_waiter *waiter)
{
- rb_add_cached(&waiter->tree_entry, &lock->waiters, __waiter_less);
+ lockdep_assert_held(&lock->wait_lock);
+
+ rb_add_cached(&waiter->tree.entry, &lock->waiters, __waiter_less);
}
static __always_inline void
rt_mutex_dequeue(struct rt_mutex_base *lock, struct rt_mutex_waiter *waiter)
{
- if (RB_EMPTY_NODE(&waiter->tree_entry))
+ lockdep_assert_held(&lock->wait_lock);
+
+ if (RB_EMPTY_NODE(&waiter->tree.entry))
return;
- rb_erase_cached(&waiter->tree_entry, &lock->waiters);
- RB_CLEAR_NODE(&waiter->tree_entry);
+ rb_erase_cached(&waiter->tree.entry, &lock->waiters);
+ RB_CLEAR_NODE(&waiter->tree.entry);
}
-#define __node_2_pi_waiter(node) \
- rb_entry((node), struct rt_mutex_waiter, pi_tree_entry)
+#define __node_2_rt_node(node) \
+ rb_entry((node), struct rt_waiter_node, entry)
-static __always_inline bool
-__pi_waiter_less(struct rb_node *a, const struct rb_node *b)
+static __always_inline bool __pi_waiter_less(struct rb_node *a, const struct rb_node *b)
{
- return rt_mutex_waiter_less(__node_2_pi_waiter(a), __node_2_pi_waiter(b));
+ return rt_waiter_node_less(__node_2_rt_node(a), __node_2_rt_node(b));
}
static __always_inline void
rt_mutex_enqueue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter)
{
- rb_add_cached(&waiter->pi_tree_entry, &task->pi_waiters, __pi_waiter_less);
+ lockdep_assert_held(&task->pi_lock);
+
+ rb_add_cached(&waiter->pi_tree.entry, &task->pi_waiters, __pi_waiter_less);
}
static __always_inline void
rt_mutex_dequeue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter)
{
- if (RB_EMPTY_NODE(&waiter->pi_tree_entry))
+ lockdep_assert_held(&task->pi_lock);
+
+ if (RB_EMPTY_NODE(&waiter->pi_tree.entry))
return;
- rb_erase_cached(&waiter->pi_tree_entry, &task->pi_waiters);
- RB_CLEAR_NODE(&waiter->pi_tree_entry);
+ rb_erase_cached(&waiter->pi_tree.entry, &task->pi_waiters);
+ RB_CLEAR_NODE(&waiter->pi_tree.entry);
}
-static __always_inline void rt_mutex_adjust_prio(struct task_struct *p)
+static __always_inline void rt_mutex_adjust_prio(struct rt_mutex_base *lock,
+ struct task_struct *p)
{
struct task_struct *pi_task = NULL;
+ lockdep_assert_held(&lock->wait_lock);
+ lockdep_assert(rt_mutex_owner(lock) == p);
lockdep_assert_held(&p->pi_lock);
if (task_has_pi_waiters(p))
* Chain walk basics and protection scope
*
* [R] refcount on task
- * [P] task->pi_lock held
+ * [Pn] task->pi_lock held
* [L] rtmutex->wait_lock held
*
+ * Normal locking order:
+ *
+ * rtmutex->wait_lock
+ * task->pi_lock
+ *
* Step Description Protected by
* function arguments:
* @task [R]
* again:
* loop_sanity_check();
* retry:
- * [1] lock(task->pi_lock); [R] acquire [P]
- * [2] waiter = task->pi_blocked_on; [P]
- * [3] check_exit_conditions_1(); [P]
- * [4] lock = waiter->lock; [P]
- * [5] if (!try_lock(lock->wait_lock)) { [P] try to acquire [L]
- * unlock(task->pi_lock); release [P]
+ * [1] lock(task->pi_lock); [R] acquire [P1]
+ * [2] waiter = task->pi_blocked_on; [P1]
+ * [3] check_exit_conditions_1(); [P1]
+ * [4] lock = waiter->lock; [P1]
+ * [5] if (!try_lock(lock->wait_lock)) { [P1] try to acquire [L]
+ * unlock(task->pi_lock); release [P1]
* goto retry;
* }
- * [6] check_exit_conditions_2(); [P] + [L]
- * [7] requeue_lock_waiter(lock, waiter); [P] + [L]
- * [8] unlock(task->pi_lock); release [P]
+ * [6] check_exit_conditions_2(); [P1] + [L]
+ * [7] requeue_lock_waiter(lock, waiter); [P1] + [L]
+ * [8] unlock(task->pi_lock); release [P1]
* put_task_struct(task); release [R]
* [9] check_exit_conditions_3(); [L]
* [10] task = owner(lock); [L]
* get_task_struct(task); [L] acquire [R]
- * lock(task->pi_lock); [L] acquire [P]
- * [11] requeue_pi_waiter(tsk, waiters(lock));[P] + [L]
- * [12] check_exit_conditions_4(); [P] + [L]
- * [13] unlock(task->pi_lock); release [P]
+ * lock(task->pi_lock); [L] acquire [P2]
+ * [11] requeue_pi_waiter(tsk, waiters(lock));[P2] + [L]
+ * [12] check_exit_conditions_4(); [P2] + [L]
+ * [13] unlock(task->pi_lock); release [P2]
* unlock(lock->wait_lock); release [L]
* goto again;
+ *
+ * Where P1 is the blocking task and P2 is the lock owner; going up one step
+ * the owner becomes the next blocked task etc..
+ *
+*
*/
static int __sched rt_mutex_adjust_prio_chain(struct task_struct *task,
enum rtmutex_chainwalk chwalk,
* enabled we continue, but stop the requeueing in the chain
* walk.
*/
- if (rt_mutex_waiter_equal(waiter, task_to_waiter(task))) {
+ if (rt_waiter_node_equal(&waiter->tree, task_to_waiter_node(task))) {
if (!detect_deadlock)
goto out_unlock_pi;
else
}
/*
- * [4] Get the next lock
+ * [4] Get the next lock; per holding task->pi_lock we can't unblock
+ * and guarantee @lock's existence.
*/
lock = waiter->lock;
/*
* [5] We need to trylock here as we are holding task->pi_lock,
* which is the reverse lock order versus the other rtmutex
* operations.
+ *
+ * Per the above, holding task->pi_lock guarantees lock exists, so
+ * inverting this lock order is infeasible from a life-time
+ * perspective.
*/
if (!raw_spin_trylock(&lock->wait_lock)) {
raw_spin_unlock_irq(&task->pi_lock);
* or
*
* DL CBS enforcement advancing the effective deadline.
- *
- * Even though pi_waiters also uses these fields, and that tree is only
- * updated in [11], we can do this here, since we hold [L], which
- * serializes all pi_waiters access and rb_erase() does not care about
- * the values of the node being removed.
*/
waiter_update_prio(waiter, task);
rt_mutex_enqueue(lock, waiter);
- /* [8] Release the task */
+ /*
+ * [8] Release the (blocking) task in preparation for
+ * taking the owner task in [10].
+ *
+ * Since we hold lock->waiter_lock, task cannot unblock, even if we
+ * release task->pi_lock.
+ */
raw_spin_unlock(&task->pi_lock);
put_task_struct(task);
return 0;
}
- /* [10] Grab the next task, i.e. the owner of @lock */
+ /*
+ * [10] Grab the next task, i.e. the owner of @lock
+ *
+ * Per holding lock->wait_lock and checking for !owner above, there
+ * must be an owner and it cannot go away.
+ */
task = get_task_struct(rt_mutex_owner(lock));
raw_spin_lock(&task->pi_lock);
* and adjust the priority of the owner.
*/
rt_mutex_dequeue_pi(task, prerequeue_top_waiter);
+ waiter_clone_prio(waiter, task);
rt_mutex_enqueue_pi(task, waiter);
- rt_mutex_adjust_prio(task);
+ rt_mutex_adjust_prio(lock, task);
} else if (prerequeue_top_waiter == waiter) {
/*
*/
rt_mutex_dequeue_pi(task, waiter);
waiter = rt_mutex_top_waiter(lock);
+ waiter_clone_prio(waiter, task);
rt_mutex_enqueue_pi(task, waiter);
- rt_mutex_adjust_prio(task);
+ rt_mutex_adjust_prio(lock, task);
} else {
/*
* Nothing changed. No need to do any priority
waiter->task = task;
waiter->lock = lock;
waiter_update_prio(waiter, task);
+ waiter_clone_prio(waiter, task);
/* Get the top priority waiter on the lock */
if (rt_mutex_has_waiters(lock))
rt_mutex_dequeue_pi(owner, top_waiter);
rt_mutex_enqueue_pi(owner, waiter);
- rt_mutex_adjust_prio(owner);
+ rt_mutex_adjust_prio(lock, owner);
if (owner->pi_blocked_on)
chain_walk = 1;
} else if (rt_mutex_cond_detect_deadlock(waiter, chwalk)) {
{
struct rt_mutex_waiter *waiter;
+ lockdep_assert_held(&lock->wait_lock);
+
raw_spin_lock(¤t->pi_lock);
waiter = rt_mutex_top_waiter(lock);
* task unblocks.
*/
rt_mutex_dequeue_pi(current, waiter);
- rt_mutex_adjust_prio(current);
+ rt_mutex_adjust_prio(lock, current);
/*
* As we are waking up the top waiter, and the waiter stays
if (rt_mutex_has_waiters(lock))
rt_mutex_enqueue_pi(owner, rt_mutex_top_waiter(lock));
- rt_mutex_adjust_prio(owner);
+ rt_mutex_adjust_prio(lock, owner);
/* Store the lock on which owner is blocked or NULL */
next_lock = task_blocked_on_lock(owner);
#include <linux/rtmutex.h>
#include <linux/sched/wake_q.h>
+
+/*
+ * This is a helper for the struct rt_mutex_waiter below. A waiter goes in two
+ * separate trees and they need their own copy of the sort keys because of
+ * different locking requirements.
+ *
+ * @entry: rbtree node to enqueue into the waiters tree
+ * @prio: Priority of the waiter
+ * @deadline: Deadline of the waiter if applicable
+ *
+ * See rt_waiter_node_less() and waiter_*_prio().
+ */
+struct rt_waiter_node {
+ struct rb_node entry;
+ int prio;
+ u64 deadline;
+};
+
/*
* This is the control structure for tasks blocked on a rt_mutex,
* which is allocated on the kernel stack on of the blocked task.
*
- * @tree_entry: pi node to enqueue into the mutex waiters tree
- * @pi_tree_entry: pi node to enqueue into the mutex owner waiters tree
+ * @tree: node to enqueue into the mutex waiters tree
+ * @pi_tree: node to enqueue into the mutex owner waiters tree
* @task: task reference to the blocked task
* @lock: Pointer to the rt_mutex on which the waiter blocks
* @wake_state: Wakeup state to use (TASK_NORMAL or TASK_RTLOCK_WAIT)
- * @prio: Priority of the waiter
- * @deadline: Deadline of the waiter if applicable
* @ww_ctx: WW context pointer
+ *
+ * @tree is ordered by @lock->wait_lock
+ * @pi_tree is ordered by rt_mutex_owner(@lock)->pi_lock
*/
struct rt_mutex_waiter {
- struct rb_node tree_entry;
- struct rb_node pi_tree_entry;
+ struct rt_waiter_node tree;
+ struct rt_waiter_node pi_tree;
struct task_struct *task;
struct rt_mutex_base *lock;
unsigned int wake_state;
- int prio;
- u64 deadline;
struct ww_acquire_ctx *ww_ctx;
};
{
struct rb_node *leftmost = rb_first_cached(&lock->waiters);
- return rb_entry(leftmost, struct rt_mutex_waiter, tree_entry) == waiter;
+ return rb_entry(leftmost, struct rt_mutex_waiter, tree.entry) == waiter;
}
static inline struct rt_mutex_waiter *rt_mutex_top_waiter(struct rt_mutex_base *lock)
struct rb_node *leftmost = rb_first_cached(&lock->waiters);
struct rt_mutex_waiter *w = NULL;
+ lockdep_assert_held(&lock->wait_lock);
+
if (leftmost) {
- w = rb_entry(leftmost, struct rt_mutex_waiter, tree_entry);
+ w = rb_entry(leftmost, struct rt_mutex_waiter, tree.entry);
BUG_ON(w->lock != lock);
}
return w;
static inline struct rt_mutex_waiter *task_top_pi_waiter(struct task_struct *p)
{
+ lockdep_assert_held(&p->pi_lock);
+
return rb_entry(p->pi_waiters.rb_leftmost, struct rt_mutex_waiter,
- pi_tree_entry);
+ pi_tree.entry);
}
#define RT_MUTEX_HAS_WAITERS 1UL
static inline void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
{
debug_rt_mutex_init_waiter(waiter);
- RB_CLEAR_NODE(&waiter->pi_tree_entry);
- RB_CLEAR_NODE(&waiter->tree_entry);
+ RB_CLEAR_NODE(&waiter->pi_tree.entry);
+ RB_CLEAR_NODE(&waiter->tree.entry);
waiter->wake_state = TASK_NORMAL;
waiter->task = NULL;
}
projects / thirdparty / kernel / stable.git / commitdiff
