Release 4.15 kernel/locking/rtmutex.c
/*
* RT-Mutexes: simple blocking mutual exclusion locks with PI support
*
* started by Ingo Molnar and Thomas Gleixner.
*
* Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
* Copyright (C) 2005-2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
* Copyright (C) 2005 Kihon Technologies Inc., Steven Rostedt
* Copyright (C) 2006 Esben Nielsen
*
* See Documentation/locking/rt-mutex-design.txt for details.
*/
#include <linux/spinlock.h>
#include <linux/export.h>
#include <linux/sched/signal.h>
#include <linux/sched/rt.h>
#include <linux/sched/deadline.h>
#include <linux/sched/wake_q.h>
#include <linux/sched/debug.h>
#include <linux/timer.h>
#include "rtmutex_common.h"
/*
* lock->owner state tracking:
*
* lock->owner holds the task_struct pointer of the owner. Bit 0
* is used to keep track of the "lock has waiters" state.
*
* owner bit0
* NULL 0 lock is free (fast acquire possible)
* NULL 1 lock is free and has waiters and the top waiter
* is going to take the lock*
* taskpointer 0 lock is held (fast release possible)
* taskpointer 1 lock is held and has waiters**
*
* The fast atomic compare exchange based acquire and release is only
* possible when bit 0 of lock->owner is 0.
*
* (*) It also can be a transitional state when grabbing the lock
* with ->wait_lock is held. To prevent any fast path cmpxchg to the lock,
* we need to set the bit0 before looking at the lock, and the owner may be
* NULL in this small time, hence this can be a transitional state.
*
* (**) There is a small time when bit 0 is set but there are no
* waiters. This can happen when grabbing the lock in the slow path.
* To prevent a cmpxchg of the owner releasing the lock, we need to
* set this bit before looking at the lock.
*/
static void
rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner)
{
unsigned long val = (unsigned long)owner;
if (rt_mutex_has_waiters(lock))
val |= RT_MUTEX_HAS_WAITERS;
lock->owner = (struct task_struct *)val;
}
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static inline void clear_rt_mutex_waiters(struct rt_mutex *lock)
{
lock->owner = (struct task_struct *)
((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS);
}
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static void fixup_rt_mutex_waiters(struct rt_mutex *lock)
{
unsigned long owner, *p = (unsigned long *) &lock->owner;
if (rt_mutex_has_waiters(lock))
return;
/*
* The rbtree has no waiters enqueued, now make sure that the
* lock->owner still has the waiters bit set, otherwise the
* following can happen:
*
* CPU 0 CPU 1 CPU2
* l->owner=T1
* rt_mutex_lock(l)
* lock(l->lock)
* l->owner = T1 | HAS_WAITERS;
* enqueue(T2)
* boost()
* unlock(l->lock)
* block()
*
* rt_mutex_lock(l)
* lock(l->lock)
* l->owner = T1 | HAS_WAITERS;
* enqueue(T3)
* boost()
* unlock(l->lock)
* block()
* signal(->T2) signal(->T3)
* lock(l->lock)
* dequeue(T2)
* deboost()
* unlock(l->lock)
* lock(l->lock)
* dequeue(T3)
* ==> wait list is empty
* deboost()
* unlock(l->lock)
* lock(l->lock)
* fixup_rt_mutex_waiters()
* if (wait_list_empty(l) {
* l->owner = owner
* owner = l->owner & ~HAS_WAITERS;
* ==> l->owner = T1
* }
* lock(l->lock)
* rt_mutex_unlock(l) fixup_rt_mutex_waiters()
* if (wait_list_empty(l) {
* owner = l->owner & ~HAS_WAITERS;
* cmpxchg(l->owner, T1, NULL)
* ===> Success (l->owner = NULL)
*
* l->owner = owner
* ==> l->owner = T1
* }
*
* With the check for the waiter bit in place T3 on CPU2 will not
* overwrite. All tasks fiddling with the waiters bit are
* serialized by l->lock, so nothing else can modify the waiters
* bit. If the bit is set then nothing can change l->owner either
* so the simple RMW is safe. The cmpxchg() will simply fail if it
* happens in the middle of the RMW because the waiters bit is
* still set.
*/
owner = READ_ONCE(*p);
if (owner & RT_MUTEX_HAS_WAITERS)
WRITE_ONCE(*p, owner & ~RT_MUTEX_HAS_WAITERS);
}
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/*
* We can speed up the acquire/release, if there's no debugging state to be
* set up.
*/
#ifndef CONFIG_DEBUG_RT_MUTEXES
# define rt_mutex_cmpxchg_relaxed(l,c,n) (cmpxchg_relaxed(&l->owner, c, n) == c)
# define rt_mutex_cmpxchg_acquire(l,c,n) (cmpxchg_acquire(&l->owner, c, n) == c)
# define rt_mutex_cmpxchg_release(l,c,n) (cmpxchg_release(&l->owner, c, n) == c)
/*
* Callers must hold the ->wait_lock -- which is the whole purpose as we force
* all future threads that attempt to [Rmw] the lock to the slowpath. As such
* relaxed semantics suffice.
*/
static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
{
unsigned long owner, *p = (unsigned long *) &lock->owner;
do {
owner = *p;
} while (cmpxchg_relaxed(p, owner,
owner | RT_MUTEX_HAS_WAITERS) != owner);
}
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/*
* Safe fastpath aware unlock:
* 1) Clear the waiters bit
* 2) Drop lock->wait_lock
* 3) Try to unlock the lock with cmpxchg
*/
static inline bool unlock_rt_mutex_safe(struct rt_mutex *lock,
unsigned long flags)
__releases(lock->wait_lock)
{
struct task_struct *owner = rt_mutex_owner(lock);
clear_rt_mutex_waiters(lock);
raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
/*
* If a new waiter comes in between the unlock and the cmpxchg
* we have two situations:
*
* unlock(wait_lock);
* lock(wait_lock);
* cmpxchg(p, owner, 0) == owner
* mark_rt_mutex_waiters(lock);
* acquire(lock);
* or:
*
* unlock(wait_lock);
* lock(wait_lock);
* mark_rt_mutex_waiters(lock);
*
* cmpxchg(p, owner, 0) != owner
* enqueue_waiter();
* unlock(wait_lock);
* lock(wait_lock);
* wake waiter();
* unlock(wait_lock);
* lock(wait_lock);
* acquire(lock);
*/
return rt_mutex_cmpxchg_release(lock, owner, NULL);
}
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#else
# define rt_mutex_cmpxchg_relaxed(l,c,n) (0)
# define rt_mutex_cmpxchg_acquire(l,c,n) (0)
# define rt_mutex_cmpxchg_release(l,c,n) (0)
static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
{
lock->owner = (struct task_struct *)
((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS);
}
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/*
* Simple slow path only version: lock->owner is protected by lock->wait_lock.
*/
static inline bool unlock_rt_mutex_safe(struct rt_mutex *lock,
unsigned long flags)
__releases(lock->wait_lock)
{
lock->owner = NULL;
raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
return true;
}
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#endif
/*
* Only use with rt_mutex_waiter_{less,equal}()
*/
#define task_to_waiter(p) \
&(struct rt_mutex_waiter){ .prio = (p)->prio, .deadline = (p)->dl.deadline }
static inline int
rt_mutex_waiter_less(struct rt_mutex_waiter *left,
struct rt_mutex_waiter *right)
{
if (left->prio < right->prio)
return 1;
/*
* If both waiters have dl_prio(), we check the deadlines of the
* associated tasks.
* If left waiter has a dl_prio(), and we didn't return 1 above,
* then right waiter has a dl_prio() too.
*/
if (dl_prio(left->prio))
return dl_time_before(left->deadline, right->deadline);
return 0;
}
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static inline int
rt_mutex_waiter_equal(struct rt_mutex_waiter *left,
struct rt_mutex_waiter *right)
{
if (left->prio != right->prio)
return 0;
/*
* If both waiters have dl_prio(), we check the deadlines of the
* associated tasks.
* If left waiter has a dl_prio(), and we didn't return 0 above,
* then right waiter has a dl_prio() too.
*/
if (dl_prio(left->prio))
return left->deadline == right->deadline;
return 1;
}
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static void
rt_mutex_enqueue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter)
{
struct rb_node **link = &lock->waiters.rb_root.rb_node;
struct rb_node *parent = NULL;
struct rt_mutex_waiter *entry;
bool leftmost = true;
while (*link) {
parent = *link;
entry = rb_entry(parent, struct rt_mutex_waiter, tree_entry);
if (rt_mutex_waiter_less(waiter, entry)) {
link = &parent->rb_left;
} else {
link = &parent->rb_right;
leftmost = false;
}
}
rb_link_node(&waiter->tree_entry, parent, link);
rb_insert_color_cached(&waiter->tree_entry, &lock->waiters, leftmost);
}
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static void
rt_mutex_dequeue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter)
{
if (RB_EMPTY_NODE(&waiter->tree_entry))
return;
rb_erase_cached(&waiter->tree_entry, &lock->waiters);
RB_CLEAR_NODE(&waiter->tree_entry);
}
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static void
rt_mutex_enqueue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter)
{
struct rb_node **link = &task->pi_waiters.rb_root.rb_node;
struct rb_node *parent = NULL;
struct rt_mutex_waiter *entry;
bool leftmost = true;
while (*link) {
parent = *link;
entry = rb_entry(parent, struct rt_mutex_waiter, pi_tree_entry);
if (rt_mutex_waiter_less(waiter, entry)) {
link = &parent->rb_left;
} else {
link = &parent->rb_right;
leftmost = false;
}
}
rb_link_node(&waiter->pi_tree_entry, parent, link);
rb_insert_color_cached(&waiter->pi_tree_entry, &task->pi_waiters, leftmost);
}
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static void
rt_mutex_dequeue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter)
{
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);
}
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| Total | 48 | 100.00% | 3 | 100.00% |
static void rt_mutex_adjust_prio(struct task_struct *p)
{
struct task_struct *pi_task = NULL;
lockdep_assert_held(&p->pi_lock);
if (task_has_pi_waiters(p))
pi_task = task_top_pi_waiter(p)->task;
rt_mutex_setprio(p, pi_task);
}
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| Ingo Molnar | 15 | 30.61% | 1 | 20.00% |
| Xunlei Pang | 13 | 26.53% | 1 | 20.00% |
| Thomas Gleixner | 2 | 4.08% | 2 | 40.00% |
| Total | 49 | 100.00% | 5 | 100.00% |
/*
* Deadlock detection is conditional:
*
* If CONFIG_DEBUG_RT_MUTEXES=n, deadlock detection is only conducted
* if the detect argument is == RT_MUTEX_FULL_CHAINWALK.
*
* If CONFIG_DEBUG_RT_MUTEXES=y, deadlock detection is always
* conducted independent of the detect argument.
*
* If the waiter argument is NULL this indicates the deboost path and
* deadlock detection is disabled independent of the detect argument
* and the config settings.
*/
static bool rt_mutex_cond_detect_deadlock(struct rt_mutex_waiter *waiter,
enum rtmutex_chainwalk chwalk)
{
/*
* This is just a wrapper function for the following call,
* because debug_rt_mutex_detect_deadlock() smells like a magic
* debug feature and I wanted to keep the cond function in the
* main source file along with the comments instead of having
* two of the same in the headers.
*/
return debug_rt_mutex_detect_deadlock(waiter, chwalk);
}
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/*
* Max number of times we'll walk the boosting chain:
*/
int max_lock_depth = 1024;
static inline struct rt_mutex *task_blocked_on_lock(struct task_struct *p)
{
return p->pi_blocked_on ? p->pi_blocked_on->lock : NULL;
}
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/*
* Adjust the priority chain. Also used for deadlock detection.
* Decreases task's usage by one - may thus free the task.
*
* @task: the task owning the mutex (owner) for which a chain walk is
* probably needed
* @chwalk: do we have to carry out deadlock detection?
* @orig_lock: the mutex (can be NULL if we are walking the chain to recheck
* things for a task that has just got its priority adjusted, and
* is waiting on a mutex)
* @next_lock: the mutex on which the owner of @orig_lock was blocked before
* we dropped its pi_lock. Is never dereferenced, only used for
* comparison to detect lock chain changes.
* @orig_waiter: rt_mutex_waiter struct for the task that has just donated
* its priority to the mutex owner (can be NULL in the case
* depicted above or if the top waiter is gone away and we are
* actually deboosting the owner)
* @top_task: the current top waiter
*
* Returns 0 or -EDEADLK.
*
* Chain walk basics and protection scope
*
* [R] refcount on task
* [P] task->pi_lock held
* [L] rtmutex->wait_lock held
*
* Step Description Protected by
* function arguments:
* @task [R]
* @orig_lock if != NULL @top_task is blocked on it
* @next_lock Unprotected. Cannot be
* dereferenced. Only used for
* comparison.
* @orig_waiter if != NULL @top_task is blocked on it
* @top_task current, or in case of proxy
* locking protected by calling
* code
* 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]
* goto retry;
* }
* [6] check_exit_conditions_2(); [P] + [L]
* [7] requeue_lock_waiter(lock, waiter); [P] + [L]
* [8] unlock(task->pi_lock); release [P]
* 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]
* unlock(lock->wait_lock); release [L]
* goto again;
*/
static int rt_mutex_adjust_prio_chain(struct task_struct *task,
enum rtmutex_chainwalk chwalk,
struct rt_mutex *orig_lock,
struct rt_mutex *next_lock,
struct rt_mutex_waiter *orig_waiter,
struct task_struct *top_task)
{
struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter;
struct rt_mutex_waiter *prerequeue_top_waiter;
int ret = 0, depth = 0;
struct rt_mutex *lock;
bool detect_deadlock;
bool requeue = true;
detect_deadlock = rt_mutex_cond_detect_deadlock(orig_waiter, chwalk);
/*
* The (de)boosting is a step by step approach with a lot of
* pitfalls. We want this to be preemptible and we want hold a
* maximum of two locks per step. So we have to check
* carefully whether things change under us.
*/
again:
/*
* We limit the lock chain length for each invocation.
*/
if (++depth > max_lock_depth) {
static int prev_max;
/*
* Print this only once. If the admin changes the limit,
* print a new message when reaching the limit again.
*/
if (prev_max != max_lock_depth) {
prev_max = max_lock_depth;
printk(KERN_WARNING "Maximum lock depth %d reached "
"task: %s (%d)\n", max_lock_depth,
top_task->comm, task_pid_nr(top_task));
}
put_task_struct(task);
return -EDEADLK;
}
/*
* We are fully preemptible here and only hold the refcount on
* @task. So everything can have changed under us since the
* caller or our own code below (goto retry/again) dropped all
* locks.
*/
retry:
/*
* [1] Task cannot go away as we did a get_task() before !
*/
raw_spin_lock_irq(&task->pi_lock);
/*
* [2] Get the waiter on which @task is blocked on.
*/
waiter = task->pi_blocked_on;
/*
* [3] check_exit_conditions_1() protected by task->pi_lock.
*/
/*
* Check whether the end of the boosting chain has been
* reached or the state of the chain has changed while we
* dropped the locks.
*/
if (!waiter)
goto out_unlock_pi;
/*
* Check the orig_waiter state. After we dropped the locks,
* the previous owner of the lock might have released the lock.
*/
if (orig_waiter && !rt_mutex_owner(orig_lock))
goto out_unlock_pi;
/*
* We dropped all locks after taking a refcount on @task, so
* the task might have moved on in the lock chain or even left
* the chain completely and blocks now on an unrelated lock or
* on @orig_lock.
*
* We stored the lock on which @task was blocked in @next_lock,
* so we can detect the chain change.
*/
if (next_lock != waiter->lock)
goto out_unlock_pi;
/*
* Drop out, when the task has no waiters. Note,
* top_waiter can be NULL, when we are in the deboosting
* mode!
*/
if (top_waiter) {
if (!task_has_pi_waiters(task))
goto out_unlock_pi;
/*
* If deadlock detection is off, we stop here if we
* are not the top pi waiter of the task. If deadlock
* detection is enabled we continue, but stop the
* requeueing in the chain walk.
*/
if (top_waiter != task_top_pi_waiter(task)) {
if (!detect_deadlock)
goto out_unlock_pi;
else
requeue = false;
}
}
/*
* If the waiter priority is the same as the task priority
* then there is no further priority adjustment necessary. If
* deadlock detection is off, we stop the chain walk. If its
* enabled we continue, but stop the requeueing in the chain
* walk.
*/
if (rt_mutex_waiter_equal(waiter, task_to_waiter(task))) {
if (!detect_deadlock)
goto out_unlock_pi;
else
requeue = false;
}
/*
* [4] Get the next lock
*/
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.
*/
if (!raw_spin_trylock(&lock->wait_lock)) {
raw_spin_unlock_irq(&task->pi_lock);
cpu_relax();
goto retry;
}
/*
* [6] check_exit_conditions_2() protected by task->pi_lock and
* lock->wait_lock.
*
* Deadlock detection. If the lock is the same as the original
* lock which caused us to walk the lock chain or if the
* current lock is owned by the task which initiated the chain
* walk, we detected a deadlock.
*/
if (lock == orig_lock || rt_mutex_owner(lock) == top_task) {
debug_rt_mutex_deadlock(chwalk, orig_waiter, lock);
raw_spin_unlock(&lock->wait_lock);
ret = -EDEADLK;
goto out_unlock_pi;
}
/*
* If we just follow the lock chain for deadlock detection, no
* need to do all the requeue operations. To avoid a truckload
* of conditionals around the various places below, just do the
* minimum chain walk checks.
*/
if (!requeue) {
/*
* No requeue[7] here. Just release @task [8]
*/
raw_spin_unlock(&task->pi_lock);
put_task_struct(task);
/*
* [9] check_exit_conditions_3 protected by lock->wait_lock.
* If there is no owner of the lock, end of chain.
*/
if (!rt_mutex_owner(lock)) {
raw_spin_unlock_irq(&lock->wait_lock);
return 0;
}
/* [10] Grab the next task, i.e. owner of @lock */
task = rt_mutex_owner(lock);
get_task_struct(task);
raw_spin_lock(&task->pi_lock);
/*
* No requeue [11] here. We just do deadlock detection.
*
* [12] Store whether owner is blocked
* itself. Decision is made after dropping the locks
*/
next_lock = task_blocked_on_lock(task);
/*
* Get the top waiter for the next iteration
*/
top_waiter = rt_mutex_top_waiter(lock);
/* [13] Drop locks */
raw_spin_unlock(&task->pi_lock);
raw_spin_unlock_irq(&lock->wait_lock);
/* If owner is not blocked, end of chain. */
if (!next_lock)
goto out_put_task;
goto again;
}
/*
* Store the current top waiter before doing the requeue
* operation on @lock. We need it for the boost/deboost
* decision below.
*/
prerequeue_top_waiter = rt_mutex_top_waiter(lock);
/* [7] Requeue the waiter in the lock waiter tree. */
rt_mutex_dequeue(lock, waiter);
/*
* Update the waiter prio fields now that we're dequeued.
*
* These values can have changed through either:
*
* sys_sched_set_scheduler() / sys_sched_setattr()
*
* 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->prio = task->prio;
waiter->deadline = task->dl.deadline;
rt_mutex_enqueue(lock, waiter);
/* [8] Release the task */
raw_spin_unlock(&task->pi_lock);
put_task_struct(task);
/*
* [9] check_exit_conditions_3 protected by lock->wait_lock.
*
* We must abort the chain walk if there is no lock owner even
* in the dead lock detection case, as we have nothing to
* follow here. This is the end of the chain we are walking.
*/
if (!rt_mutex_owner(lock)) {
/*
* If the requeue [7] above changed the top waiter,
* then we need to wake the new top waiter up to try
* to get the lock.
*/
if (prerequeue_top_waiter != rt_mutex_top_waiter(lock))
wake_up_process(rt_mutex_top_waiter(lock)->task);
raw_spin_unlock_irq(&lock->wait_lock);
return 0;
}
/* [10] Grab the next task, i.e. the owner of @lock */
task = rt_mutex_owner(lock);
get_task_struct(task);
raw_spin_lock(&task->pi_lock);
/* [11] requeue the pi waiters if necessary */
if (waiter == rt_mutex_top_waiter(lock)) {
/*
* The waiter became the new top (highest priority)
* waiter on the lock. Replace the previous top waiter
* in the owner tasks pi waiters tree with this waiter
* and adjust the priority of the owner.
*/
rt_mutex_dequeue_pi(task, prerequeue_top_waiter);
rt_mutex_enqueue_pi(task, waiter);
rt_mutex_adjust_prio(task);
} else if (prerequeue_top_waiter == waiter) {
/*
* The waiter was the top waiter on the lock, but is
* no longer the top prority waiter. Replace waiter in
* the owner tasks pi waiters tree with the new top
* (highest priority) waiter and adjust the priority
* of the owner.
* The new top waiter is stored in @waiter so that
* @waiter == @top_waiter evaluates to true below and
* we continue to deboost the rest of the chain.
*/
rt_mutex_dequeue_pi(task, waiter);
waiter = rt_mutex_top_waiter(lock);
rt_mutex_enqueue_pi(task, waiter);
rt_mutex_adjust_prio(task);
} else {
/*
* Nothing changed. No need to do any priority
* adjustment.
*/
}
/*
* [12] check_exit_conditions_4() protected by task->pi_lock
* and lock->wait_lock. The actual decisions are made after we
* dropped the locks.
*
* Check whether the task which owns the current lock is pi
* blocked itself. If yes we store a pointer to the lock for
* the lock chain change detection above. After we dropped
* task->pi_lock next_lock cannot be dereferenced anymore.
*/
next_lock = task_blocked_on_lock(task);
/*
* Store the top waiter of @lock for the end of chain walk
* decision below.
*/
top_waiter = rt_mutex_top_waiter(lock);
/* [13] Drop the locks */
raw_spin_unlock(&task->pi_lock);
raw_spin_unlock_irq(&lock->wait_lock);
/*
* Make the actual exit decisions [12], based on the stored
* values.
*
* We reached the end of the lock chain. Stop right here. No
* point to go back just to figure that out.
*/
if (!next_lock)
goto out_put_task;
/*
* If the current waiter is not the top waiter on the lock,
* then we can stop the chain walk here if we are not in full
* deadlock detection mode.
*/
if (!detect_deadlock && waiter != top_waiter)
goto out_put_task;
goto again;
out_unlock_pi:
raw_spin_unlock_irq(&task->pi_lock);
out_put_task:
put_task_struct(task);
return ret;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Ingo Molnar | 356 | 49.51% | 2 | 8.70% |
| Thomas Gleixner | 274 | 38.11% | 12 | 52.17% |
| Lai Jiangshan | 40 | 5.56% | 1 | 4.35% |
| Peter Zijlstra | 35 | 4.87% | 4 | 17.39% |
| Steven Rostedt | 5 | 0.70% | 1 | 4.35% |
| Davidlohr Bueso A | 3 | 0.42% | 1 | 4.35% |
| Pavel Emelyanov | 3 | 0.42% | 1 | 4.35% |
| Xunlei Pang | 3 | 0.42% | 1 | 4.35% |
| Total | 719 | 100.00% | 23 | 100.00% |
/*
* Try to take an rt-mutex
*
* Must be called with lock->wait_lock held and interrupts disabled
*
* @lock: The lock to be acquired.
* @task: The task which wants to acquire the lock
* @waiter: The waiter that is queued to the lock's wait tree if the
* callsite called task_blocked_on_lock(), otherwise NULL
*/
static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task,
struct rt_mutex_waiter *waiter)
{
lockdep_assert_held(&lock->wait_lock);
/*
* Before testing whether we can acquire @lock, we set the
* RT_MUTEX_HAS_WAITERS bit in @lock->owner. This forces all
* other tasks which try to modify @lock into the slow path
* and they serialize on @lock->wait_lock.
*
* The RT_MUTEX_HAS_WAITERS bit can have a transitional state
* as explained at the top of this file if and only if:
*
* - There is a lock owner. The caller must fixup the
* transient state if it does a trylock or leaves the lock
* function due to a signal or timeout.
*
* - @task acquires the lock and there are no other
* waiters. This is undone in rt_mutex_set_owner(@task) at
* the end of this function.
*/
mark_rt_mutex_waiters(lock);
/*
* If @lock has an owner, give up.
*/
if (rt_mutex_owner(lock))
return 0;
/*
* If @waiter != NULL, @task has already enqueued the waiter
* into @lock waiter tree. If @waiter == NULL then this is a
* trylock attempt.
*/
if (waiter) {
/*
* If waiter is not the highest priority waiter of
* @lock, give up.
*/
if (waiter != rt_mutex_top_waiter(lock))
return 0;
/*
* We can acquire the lock. Remove the waiter from the
* lock waiters tree.
*/
rt_mutex_dequeue(lock, waiter);
} else {
/*
* If the lock has waiters already we check whether @task is
* eligible to take over the lock.
*
* If there are no other waiters, @task can acquire
* the lock. @task->pi_blocked_on is NULL, so it does
* not need to be dequeued.
*/
if (rt_mutex_has_waiters(lock)) {
/*
* If @task->prio is greater than or equal to
* the top waiter priority (kernel view),
* @task lost.
*/
if (!rt_mutex_waiter_less(task_to_waiter(task),
rt_mutex_top_waiter(lock)))
return 0;
/*
* The current top waiter stays enqueued. We
* don't have to change anything in the lock
* waiters order.
*/
} else {
/*
* No waiters. Take the lock without the
* pi_lock dance.@task->pi_blocked_on is NULL
* and we have no waiters to enqueue in @task
* pi waiters tree.
*/
goto takeit;
}
}
/*
* Clear @task->pi_blocked_on. Requires protection by
* @task->pi_lock. Redundant operation for the @waiter == NULL
* case, but conditionals are more expensive than a redundant
* store.
*/
raw_spin_lock(&task->pi_lock);
task->pi_blocked_on = NULL;
/*
* Finish the lock acquisition. @task is the new owner. If
* other waiters exist we have to insert the highest priority
* waiter into @task->pi_waiters tree.
*/
if (rt_mutex_has_waiters(lock))
rt_mutex_enqueue_pi(task, rt_mutex_top_waiter(lock));
raw_spin_unlock(&task->pi_lock);
takeit:
/* We got the lock. */
debug_rt_mutex_lock(lock);
/*
* This either preserves the RT_MUTEX_HAS_WAITERS bit if there
* are still waiters or clears it.
*/
rt_mutex_set_owner(lock, task);
return 1;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Ingo Molnar | 74 | 42.29% | 2 | 20.00% |
| Thomas Gleixner | 44 | 25.14% | 2 | 20.00% |
| Lai Jiangshan | 28 | 16.00% | 1 | 10.00% |
| Peter Zijlstra | 18 | 10.29% | 3 | 30.00% |
| Darren Hart | 7 | 4.00% | 1 | 10.00% |
| Davidlohr Bueso A | 4 | 2.29% | 1 | 10.00% |
| Total | 175 | 100.00% | 10 | 100.00% |
/*
* Task blocks on lock.
*
* Prepare waiter and propagate pi chain
*
* This must be called with lock->wait_lock held and interrupts disabled
*/
static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
struct rt_mutex_waiter *waiter,
struct task_struct *task,
enum rtmutex_chainwalk chwalk)
{
struct task_struct *owner = rt_mutex_owner(lock);
struct rt_mutex_waiter *top_waiter = waiter;
struct rt_mutex *next_lock;
int chain_walk = 0, res;
lockdep_assert_held(&lock->wait_lock);
/*
* Early deadlock detection. We really don't want the task to
* enqueue on itself just to untangle the mess later. It's not
* only an optimization. We drop the locks, so another waiter
* can come in before the chain walk detects the deadlock. So
* the other will detect the deadlock and return -EDEADLOCK,
* which is wrong, as the other waiter is not in a deadlock
* situation.
*/
if (owner == task)
return -EDEADLK;
raw_spin_lock(&task->pi_lock);
waiter->task = task;
waiter->lock = lock;
waiter->prio = task->prio;
waiter->deadline = task->dl.deadline;
/* Get the top priority waiter on the lock */
if (rt_mutex_has_waiters(lock))
top_waiter = rt_mutex_top_waiter(lock);
rt_mutex_enqueue(lock, waiter);
task->pi_blocked_on = waiter;
raw_spin_unlock(&task->pi_lock);
if (!owner)
return 0;
raw_spin_lock(&owner->pi_lock);
if (waiter == rt_mutex_top_waiter(lock)) {
rt_mutex_dequeue_pi(owner, top_waiter);
rt_mutex_enqueue_pi(owner, waiter);
rt_mutex_adjust_prio(owner);
if (owner->pi_blocked_on)
chain_walk = 1;
} else if (rt_mutex_cond_detect_deadlock(waiter, chwalk)) {
chain_walk = 1;
}
/* Store the lock on which owner is blocked or NULL */
next_lock = task_blocked_on_lock(owner);
raw_spin_unlock(&owner->pi_lock);
/*
* Even if full deadlock detection is on, if the owner is not
* blocked itself, we can avoid finding this out in the chain
* walk.
*/
if (!chain_walk || !next_lock)
return 0;
/*
* The owner can't disappear while holding a lock,
* so the owner struct is protected by wait_lock.
* Gets dropped in rt_mutex_adjust_prio_chain()!
*/
get_task_struct(owner);
raw_spin_unlock_irq(&lock->wait_lock);
res = rt_mutex_adjust_prio_chain(owner, chwalk, lock,
next_lock, waiter, task);
raw_spin_lock_irq(&lock->wait_lock);
return res;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Ingo Molnar | 166 | 57.44% | 3 | 20.00% |
| Thomas Gleixner | 61 | 21.11% | 5 | 33.33% |
| Peter Zijlstra | 28 | 9.69% | 3 | 20.00% |
| Steven Rostedt | 10 | 3.46% | 1 | 6.67% |
| Darren Hart | 10 | 3.46% | 1 | 6.67% |
| Dario Faggioli | 8 | 2.77% | 1 | 6.67% |
| Lai Jiangshan | 6 | 2.08% | 1 | 6.67% |
| Total | 289 | 100.00% | 15 | 100.00% |
/*
* Remove the top waiter from the current tasks pi waiter tree and
* queue it up.
*
* Called with lock->wait_lock held and interrupts disabled.
*/
static void mark_wakeup_next_waiter(struct wake_q_head *wake_q,
struct rt_mutex *lock)
{
struct rt_mutex_waiter *waiter;
raw_spin_lock(¤t->pi_lock);
waiter = rt_mutex_top_waiter(lock);
/*
* Remove it from current->pi_waiters and deboost.
*
* We must in fact deboost here in order to ensure we call
* rt_mutex_setprio() to update p->pi_top_task before the
* task unblocks.
*/
rt_mutex_dequeue_pi(current, waiter);
rt_mutex_adjust_prio(current);
/*
* As we are waking up the top waiter, and the waiter stays
* queued on the lock until it gets the lock, this lock
* obviously has waiters. Just set the bit here and this has
* the added benefit of forcing all new tasks into the
* slow path making sure no task of lower priority than
* the top waiter can steal this lock.
*/
lock->owner = (void *) RT_MUTEX_HAS_WAITERS;
/*
* We deboosted before waking the top waiter task such that we don't
* run two tasks with the 'same' priority (and ensure the
* p->pi_top_task pointer points to a blocked task). This however can
* lead to priority inversion if we would get preempted after the
* deboost but before waking our donor task, hence the preempt_disable()
* before unlock.
*
* Pairs with preempt_enable() in rt_mutex_postunlock();
*/
preempt_disable();
wake_q_add(wake_q, waiter->task);
raw_spin_unlock(¤t->pi_lock);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Lai Jiangshan | 22 | 27.16% | 1 | 12.50% |
| Ingo Molnar | 20 | 24.69% | 1 | 12.50% |
| Peter Zijlstra | 16 | 19.75% | 2 | 25.00% |
| Thomas Gleixner | 10 | 12.35% | 2 | 25.00% |
| Davidlohr Bueso A | 9 | 11.11% | 1 | 12.50% |
| Xunlei Pang | 4 | 4.94% | 1 | 12.50% |
| Total | 81 | 100.00% | 8 | 100.00% |
/*
* Remove a waiter from a lock and give up
*
* Must be called with lock->wait_lock held and interrupts disabled. I must
* have just failed to try_to_take_rt_mutex().
*/
static void remove_waiter(struct rt_mutex *lock,
struct rt_mutex_waiter *waiter)
{
bool is_top_waiter = (waiter == rt_mutex_top_waiter(lock));
struct task_struct *owner = rt_mutex_owner(lock);
struct rt_mutex *next_lock;
lockdep_assert_held(&lock->wait_lock);
raw_spin_lock(¤t->pi_lock);
rt_mutex_dequeue(lock, waiter);
current->pi_blocked_on = NULL;
raw_spin_unlock(¤t->pi_lock);
/*
* Only update priority if the waiter was the highest priority
* waiter of the lock and there is an owner to update.
*/
if (!owner || !is_top_waiter)
return;
raw_spin_lock(&owner->pi_lock);
rt_mutex_dequeue_pi(owner, waiter);
if (rt_mutex_has_waiters(lock))
rt_mutex_enqueue_pi(owner, rt_mutex_top_waiter(lock));
rt_mutex_adjust_prio(owner);
/* Store the lock on which owner is blocked or NULL */
next_lock = task_blocked_on_lock(owner);
raw_spin_unlock(&owner->pi_lock);
/*
* Don't walk the chain, if the owner task is not blocked
* itself.
*/
if (!next_lock)
return;
/* gets dropped in rt_mutex_adjust_prio_chain()! */
get_task_struct(owner);
raw_spin_unlock_irq(&lock->wait_lock);
rt_mutex_adjust_prio_chain(owner, RT_MUTEX_MIN_CHAINWALK, lock,
next_lock, NULL, current);
raw_spin_lock_irq(&lock->wait_lock);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Ingo Molnar | 127 | 67.91% | 3 | 21.43% |
| Thomas Gleixner | 34 | 18.18% | 6 | 42.86% |
| Peter Zijlstra | 17 | 9.09% | 3 | 21.43% |
| Steven Rostedt | 6 | 3.21% | 1 | 7.14% |
| Lai Jiangshan | 3 | 1.60% | 1 | 7.14% |
| Total | 187 | 100.00% | 14 | 100.00% |
/*
* Recheck the pi chain, in case we got a priority setting
*
* Called from sched_setscheduler
*/
void rt_mutex_adjust_pi(struct task_struct *task)
{
struct rt_mutex_waiter *waiter;
struct rt_mutex *next_lock;
unsigned long flags;
raw_spin_lock_irqsave(&task->pi_lock, flags);
waiter = task->pi_blocked_on;
if (!waiter || rt_mutex_waiter_equal(waiter, task_to_waiter(task))) {
raw_spin_unlock_irqrestore(&task->pi_lock, flags);
return;
}
next_lock = waiter->lock;
raw_spin_unlock_irqrestore(&task->pi_lock, flags);
/* gets dropped in rt_mutex_adjust_prio_chain()! */
get_task_struct(task);
rt_mutex_adjust_prio_chain(task, RT_MUTEX_MIN_CHAINWALK, NULL,
next_lock, NULL, task);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Thomas Gleixner | 87 | 82.86% | 4 | 50.00% |
| Steven Rostedt | 6 | 5.71% | 1 | 12.50% |
| Peter Zijlstra | 5 | 4.76% | 1 | 12.50% |
| Ingo Molnar | 5 | 4.76% | 1 | 12.50% |
| Dario Faggioli | 2 | 1.90% | 1 | 12.50% |
| Total | 105 | 100.00% | 8 | 100.00% |
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);
waiter->task = NULL;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Peter Zijlstra | 37 | 100.00% | 1 | 100.00% |
| Total | 37 | 100.00% | 1 | 100.00% |
/**
* __rt_mutex_slowlock() - Perform the wait-wake-try-to-take loop
* @lock: the rt_mutex to take
* @state: the state the task should block in (TASK_INTERRUPTIBLE
* or TASK_UNINTERRUPTIBLE)
* @timeout: the pre-initialized and started timer, or NULL for none
* @waiter: the pre-initialized rt_mutex_waiter
*
* Must be called with lock->wait_lock held and interrupts disabled
*/
static int __sched
__rt_mutex_slowlock(struct rt_mutex *lock, int state,
struct hrtimer_sleeper *timeout,
struct rt_mutex_waiter *waiter)
{
int ret = 0;
for (;;) {
/* Try to acquire the lock: */
if (try_to_take_rt_mutex(lock, current, waiter))
break;
/*
* TASK_INTERRUPTIBLE checks for signals and
* timeout. Ignored otherwise.
*/
if (likely(state == TASK_INTERRUPTIBLE)) {
/* Signal pending? */
if (signal_pending(current))
ret = -EINTR;
if (timeout && !timeout->task)
ret = -ETIMEDOUT;
if (ret)
break;
}
raw_spin_unlock_irq(&lock->wait_lock);
debug_rt_mutex_print_deadlock(waiter);
schedule();
raw_spin_lock_irq(&lock->wait_lock);
set_current_state(state);
}
__set_current_state(TASK_RUNNING);
return ret;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Ingo Molnar | 108 | 82.44% | 2 | 25.00% |
| Darren Hart | 9 | 6.87% | 1 | 12.50% |
| Davidlohr Bueso A | 7 | 5.34% | 2 | 25.00% |
| Lai Jiangshan | 4 | 3.05% | 1 | 12.50% |
| Thomas Gleixner | 2 | 1.53% | 1 | 12.50% |
| Steven Rostedt | 1 | 0.76% | 1 | 12.50% |
| Total | 131 | 100.00% | 8 | 100.00% |
static void rt_mutex_handle_deadlock(int res, int detect_deadlock,
struct rt_mutex_waiter *w)
{
/*
* If the result is not -EDEADLOCK or the caller requested
* deadlock detection, nothing to do here.
*/
if (res != -EDEADLOCK || detect_deadlock)
return;
/*
* Yell lowdly and stop the task right here.
*/
rt_mutex_print_deadlock(w);
while (1) {
set_current_state(TASK_INTERRUPTIBLE);
schedule();
}
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Thomas Gleixner | 48 | 100.00% | 1 | 100.00% |
| Total | 48 | 100.00% | 1 | 100.00% |
/*
* Slow path lock function:
*/
static int __sched
rt_mutex_slowlock(struct rt_mutex *lock, int state,
struct hrtimer_sleeper *timeout,
enum rtmutex_chainwalk chwalk)
{
struct rt_mutex_waiter waiter;
unsigned long flags;
int ret = 0;
rt_mutex_init_waiter(&waiter);
/*
* Technically we could use raw_spin_[un]lock_irq() here, but this can
* be called in early boot if the cmpxchg() fast path is disabled
* (debug, no architecture support). In this case we will acquire the
* rtmutex with lock->wait_lock held. But we cannot unconditionally
* enable interrupts in that early boot case. So we need to use the
* irqsave/restore variants.
*/
raw_spin_lock_irqsave(&lock->wait_lock, flags);
/* Try to acquire the lock again: */
if (try_to_take_rt_mutex(lock, current, NULL)) {
raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
return 0;
}
set_current_state(state);
/* Setup the timer, when timeout != NULL */
if (unlikely(timeout))
hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS);
ret = task_blocks_on_rt_mutex(lock, &waiter, current, chwalk);
if (likely(!ret))
/* sleep on the mutex */
ret = __rt_mutex_slowlock(lock, state, timeout, &waiter);
if (unlikely(ret)) {
__set_current_state(TASK_RUNNING);
if (rt_mutex_has_waiters(lock))
remove_waiter(lock, &waiter);
rt_mutex_handle_deadlock(ret, chwalk, &waiter);
}
/*
* try_to_take_rt_mutex() sets the waiter bit
* unconditionally. We might have to fix that up.
*/
fixup_rt_mutex_waiters(lock);
raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
/* Remove pending timer: */
if (unlikely(timeout))
hrtimer_cancel(&timeout->timer);
debug_rt_mutex_free_waiter(&waiter);
return ret;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Darren Hart | 109 | 49.32% | 1 | 8.33% |
| Ingo Molnar | 37 | 16.74% | 2 | 16.67% |
| Thomas Gleixner | 30 | 13.57% | 3 | 25.00% |
| Lai Jiangshan | 26 | 11.76% | 1 | 8.33% |
| Sebastian Andrzej Siewior | 12 | 5.43% | 2 | 16.67% |
| Peter Zijlstra | 6 | 2.71% | 2 | 16.67% |
| Davidlohr Bueso A | 1 | 0.45% | 1 | 8.33% |
| Total | 221 | 100.00% | 12 | 100.00% |
static inline int __rt_mutex_slowtrylock(struct rt_mutex *lock)
{
int ret = try_to_take_rt_mutex(lock, current, NULL);
/*
* try_to_take_rt_mutex() sets the lock waiters bit
* unconditionally. Clean this up.
*/
fixup_rt_mutex_waiters(lock);
return ret;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Peter Zijlstra | 33 | 100.00% | 1 | 100.00% |
| Total | 33 | 100.00% | 1 | 100.00% |
/*
* Slow path try-lock function:
*/
static inline int rt_mutex_slowtrylock(struct rt_mutex *lock)
{
unsigned long flags;
int ret;
/*
* If the lock already has an owner we fail to get the lock.
* This can be done without taking the @lock->wait_lock as
* it is only being read, and this is a trylock anyway.
*/
if (rt_mutex_owner(lock))
return 0;
/*
* The mutex has currently no owner. Lock the wait lock and try to
* acquire the lock. We use irqsave here to support early boot calls.
*/
raw_spin_lock_irqsave(&lock->wait_lock, flags);
ret = __rt_mutex_slowtrylock(lock);
raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
return ret;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Ingo Molnar | 38 | 62.30% | 1 | 25.00% |
| Thomas Gleixner | 22 | 36.07% | 2 | 50.00% |
| Peter Zijlstra | 1 | 1.64% | 1 | 25.00% |
| Total | 61 | 100.00% | 4 | 100.00% |
/*
* Slow path to release a rt-mutex.
*
* Return whether the current task needs to call rt_mutex_postunlock().
*/
static bool __sched rt_mutex_slowunlock(struct rt_mutex *lock,
struct wake_q_head *wake_q)
{
unsigned long flags;
/* irqsave required to support early boot calls */
raw_spin_lock_irqsave(&lock->wait_lock, flags);
debug_rt_mutex_unlock(lock);
/*
* We must be careful here if the fast path is enabled. If we
* have no waiters queued we cannot set owner to NULL here
* because of:
*
* foo->lock->owner = NULL;
* rtmutex_lock(foo->lock); <- fast path
* free = atomic_dec_and_test(foo->refcnt);
* rtmutex_unlock(foo->lock); <- fast path
* if (free)
* kfree(foo);
* raw_spin_unlock(foo->lock->wait_lock);
*
* So for the fastpath enabled kernel:
*
* Nothing can set the waiters bit as long as we hold
* lock->wait_lock. So we do the following sequence:
*
* owner = rt_mutex_owner(lock);
* clear_rt_mutex_waiters(lock);
* raw_spin_unlock(&lock->wait_lock);
* if (cmpxchg(&lock->owner, owner, 0) == owner)
* return;
* goto retry;
*
* The fastpath disabled variant is simple as all access to
* lock->owner is serialized by lock->wait_lock:
*
* lock->owner = NULL;
* raw_spin_unlock(&lock->wait_lock);
*/
while (!rt_mutex_has_waiters(lock)) {
/* Drops lock->wait_lock ! */
if (unlock_rt_mutex_safe(lock, flags) == true)
return false;
/* Relock the rtmutex and try again */
raw_spin_lock_irqsave(&lock->wait_lock, flags);
}
/*
* The wakeup next waiter path does not suffer from the above
* race. See the comments there.
*
* Queue the next waiter for wakeup once we release the wait_lock.
*/
mark_wakeup_next_waiter(wake_q, lock);
raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
return true; /* call rt_mutex_postunlock() */
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Ingo Molnar | 51 | 53.12% | 1 | 16.67% |
| Thomas Gleixner | 28 | 29.17% | 2 | 33.33% |
| Sebastian Andrzej Siewior | 12 | 12.50% | 1 | 16.67% |
| Davidlohr Bueso A | 4 | 4.17% | 1 | 16.67% |
| Peter Zijlstra | 1 | 1.04% | 1 | 16.67% |
| Total | 96 | 100.00% | 6 | 100.00% |
/*
* debug aware fast / slowpath lock,trylock,unlock
*
* The atomic acquire/release ops are compiled away, when either the
* architecture does not support cmpxchg or when debugging is enabled.
*/
static inline int
rt_mutex_fastlock(struct rt_mutex *lock, int state,
int (*slowfn)(struct rt_mutex *lock, int state,
struct hrtimer_sleeper *timeout,
enum rtmutex_chainwalk chwalk))
{
if (likely(rt_mutex_cmpxchg_acquire(lock, NULL, current)))
return 0;
return slowfn(lock, state, NULL, RT_MUTEX_MIN_CHAINWALK);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Ingo Molnar | 63 | 92.65% | 2 | 50.00% |
| Thomas Gleixner | 4 | 5.88% | 1 | 25.00% |
| Davidlohr Bueso A | 1 | 1.47% | 1 | 25.00% |
| Total | 68 | 100.00% | 4 | 100.00% |
static inline int
rt_mutex_timed_fastlock(struct rt_mutex *lock, int state,
struct hrtimer_sleeper *timeout,
enum rtmutex_chainwalk chwalk,
int (*slowfn)(struct rt_mutex *lock, int state,
struct hrtimer_sleeper *timeout,
enum rtmutex_chainwalk chwalk))
{
if (chwalk == RT_MUTEX_MIN_CHAINWALK &&
likely(rt_mutex_cmpxchg_acquire(lock, NULL, current)))
return 0;
return slowfn(lock, state, timeout, chwalk);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Ingo Molnar | 70 | 86.42% | 2 | 50.00% |
| Thomas Gleixner | 10 | 12.35% | 1 | 25.00% |
| Davidlohr Bueso A | 1 | 1.23% | 1 | 25.00% |
| Total | 81 | 100.00% | 4 | 100.00% |
static inline int
rt_mutex_fasttrylock(struct rt_mutex *lock,
int (*slowfn)(struct rt_mutex *lock))
{
if (likely(rt_mutex_cmpxchg_acquire(lock, NULL, current)))
return 1;
return slowfn(lock);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Ingo Molnar | 46 | 97.87% | 2 | 66.67% |
| Davidlohr Bueso A | 1 | 2.13% | 1 | 33.33% |
| Total | 47 | 100.00% | 3 | 100.00% |
/*
* Performs the wakeup of the the top-waiter and re-enables preemption.
*/
void rt_mutex_postunlock(struct wake_q_head *wake_q)
{
wake_up_q(wake_q);
/* Pairs with preempt_disable() in rt_mutex_slowunlock() */
preempt_enable();
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Xunlei Pang | 19 | 100.00% | 1 | 100.00% |
| Total | 19 | 100.00% | 1 | 100.00% |
static inline void
rt_mutex_fastunlock(struct rt_mutex *lock,
bool (*slowfn)(struct rt_mutex *lock,
struct wake_q_head *wqh))
{
DEFINE_WAKE_Q(wake_q);
if (likely(rt_mutex_cmpxchg_release(lock, current, NULL)))
return;
if (slowfn(lock, &wake_q))
rt_mutex_postunlock(&wake_q);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Ingo Molnar | 41 | 63.08% | 1 | 14.29% |
| Sebastian Andrzej Siewior | 17 | 26.15% | 1 | 14.29% |
| Peter Zijlstra | 4 | 6.15% | 2 | 28.57% |
| Davidlohr Bueso A | 1 | 1.54% | 1 | 14.29% |
| Waiman Long | 1 | 1.54% | 1 | 14.29% |
| Xunlei Pang | 1 | 1.54% | 1 | 14.29% |
| Total | 65 | 100.00% | 7 | 100.00% |
/**
* rt_mutex_lock - lock a rt_mutex
*
* @lock: the rt_mutex to be locked
*/
void __sched rt_mutex_lock(struct rt_mutex *lock)
{
might_sleep();
mutex_acquire(&lock->dep_map, 0, 0, _RET_IP_);
rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, rt_mutex_slowlock);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Ingo Molnar | 23 | 62.16% | 1 | 50.00% |
| Peter Zijlstra | 14 | 37.84% | 1 | 50.00% |
| Total | 37 | 100.00% | 2 | 100.00% |
EXPORT_SYMBOL_GPL(rt_mutex_lock);
/**
* rt_mutex_lock_interruptible - lock a rt_mutex interruptible
*
* @lock: the rt_mutex to be locked
*
* Returns:
* 0 on success
* -EINTR when interrupted by a signal
*/
int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock)
{
int ret;
might_sleep();
mutex_acquire(&lock->dep_map, 0, 0, _RET_IP_);
ret = rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE, rt_mutex_slowlock);
if (ret)
mutex_release(&lock->dep_map, 1, _RET_IP_);
return ret;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Peter Zijlstra | 38 | 62.30% | 1 | 50.00% |
| Ingo Molnar | 23 | 37.70% | 1 | 50.00% |
| Total | 61 | 100.00% | 2 | 100.00% |
EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible);
/*
* Futex variant, must not use fastpath.
*/
int __sched rt_mutex_futex_trylock(struct rt_mutex *lock)
{
return rt_mutex_slowtrylock(lock);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Peter Zijlstra | 14 | 82.35% | 1 | 50.00% |
| Thomas Gleixner | 3 | 17.65% | 1 | 50.00% |
| Total | 17 | 100.00% | 2 | 100.00% |
int __sched __rt_mutex_futex_trylock(struct rt_mutex *lock)
{
return __rt_mutex_slowtrylock(lock);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Peter Zijlstra | 17 | 100.00% | 1 | 100.00% |
| Total | 17 | 100.00% | 1 | 100.00% |
/**
* rt_mutex_timed_lock - lock a rt_mutex interruptible
* the timeout structure is provided
* by the caller
*
* @lock: the rt_mutex to be locked
* @timeout: timeout structure or NULL (no timeout)
*
* Returns:
* 0 on success
* -EINTR when interrupted by a signal
* -ETIMEDOUT when the timeout expired
*/
int
rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout)
{
int ret;
might_sleep();
mutex_acquire(&lock->dep_map, 0, 0, _RET_IP_);
ret = rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout,
RT_MUTEX_MIN_CHAINWALK,
rt_mutex_slowlock);
if (ret)
mutex_release(&lock->dep_map, 1, _RET_IP_);
return ret;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Peter Zijlstra | 38 | 55.07% | 1 | 33.33% |
| Ingo Molnar | 30 | 43.48% | 1 | 33.33% |
| Thomas Gleixner | 1 | 1.45% | 1 | 33.33% |
| Total | 69 | 100.00% | 3 | 100.00% |
EXPORT_SYMBOL_GPL(rt_mutex_timed_lock);
/**
* rt_mutex_trylock - try to lock a rt_mutex
*
* @lock: the rt_mutex to be locked
*
* This function can only be called in thread context. It's safe to
* call it from atomic regions, but not from hard interrupt or soft
* interrupt context.
*
* Returns 1 on success and 0 on contention
*/
int __sched rt_mutex_trylock(struct rt_mutex *lock)
{
int ret;
if (WARN_ON_ONCE(in_irq() || in_nmi() || in_serving_softirq()))
return 0;
ret = rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock);
if (ret)
mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_);
return ret;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Peter Zijlstra | 26 | 42.62% | 1 | 25.00% |
| Ingo Molnar | 18 | 29.51% | 1 | 25.00% |
| Thomas Gleixner | 16 | 26.23% | 1 | 25.00% |
| Sebastian Andrzej Siewior | 1 | 1.64% | 1 | 25.00% |
| Total | 61 | 100.00% | 4 | 100.00% |
EXPORT_SYMBOL_GPL(rt_mutex_trylock);
/**
* rt_mutex_unlock - unlock a rt_mutex
*
* @lock: the rt_mutex to be unlocked
*/
void __sched rt_mutex_unlock(struct rt_mutex *lock)
{
mutex_release(&lock->dep_map, 1, _RET_IP_);
rt_mutex_fastunlock(lock, rt_mutex_slowunlock);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Ingo Molnar | 18 | 60.00% | 1 | 50.00% |
| Peter Zijlstra | 12 | 40.00% | 1 | 50.00% |
| Total | 30 | 100.00% | 2 | 100.00% |
EXPORT_SYMBOL_GPL(rt_mutex_unlock);
/**
* Futex variant, that since futex variants do not use the fast-path, can be
* simple and will not need to retry.
*/
bool __sched __rt_mutex_futex_unlock(struct rt_mutex *lock,
struct wake_q_head *wake_q)
{
lockdep_assert_held(&lock->wait_lock);
debug_rt_mutex_unlock(lock);
if (!rt_mutex_has_waiters(lock)) {
lock->owner = NULL;
return false; /* done */
}
/*
* We've already deboosted, mark_wakeup_next_waiter() will
* retain preempt_disabled when we drop the wait_lock, to
* avoid inversion prior to the wakeup. preempt_disable()
* therein pairs with rt_mutex_postunlock().
*/
mark_wakeup_next_waiter(wake_q, lock);
return true; /* call postunlock() */
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Peter Zijlstra | 37 | 60.66% | 2 | 50.00% |
| Sebastian Andrzej Siewior | 23 | 37.70% | 1 | 25.00% |
| Mike Galbraith | 1 | 1.64% | 1 | 25.00% |
| Total | 61 | 100.00% | 4 | 100.00% |
void __sched rt_mutex_futex_unlock(struct rt_mutex *lock)
{
DEFINE_WAKE_Q(wake_q);
bool postunlock;
raw_spin_lock_irq(&lock->wait_lock);
postunlock = __rt_mutex_futex_unlock(lock, &wake_q);
raw_spin_unlock_irq(&lock->wait_lock);
if (postunlock)
rt_mutex_postunlock(&wake_q);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Peter Zijlstra | 49 | 89.09% | 2 | 50.00% |
| Sebastian Andrzej Siewior | 5 | 9.09% | 1 | 25.00% |
| Xunlei Pang | 1 | 1.82% | 1 | 25.00% |
| Total | 55 | 100.00% | 4 | 100.00% |
/**
* rt_mutex_destroy - mark a mutex unusable
* @lock: the mutex to be destroyed
*
* This function marks the mutex uninitialized, and any subsequent
* use of the mutex is forbidden. The mutex must not be locked when
* this function is called.
*/
void rt_mutex_destroy(struct rt_mutex *lock)
{
WARN_ON(rt_mutex_is_locked(lock));
#ifdef CONFIG_DEBUG_RT_MUTEXES
lock->magic = NULL;
#endif
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Ingo Molnar | 29 | 100.00% | 1 | 100.00% |
| Total | 29 | 100.00% | 1 | 100.00% |
EXPORT_SYMBOL_GPL(rt_mutex_destroy);
/**
* __rt_mutex_init - initialize the rt lock
*
* @lock: the rt lock to be initialized
*
* Initialize the rt lock to unlocked state.
*
* Initializing of a locked rt lock is not allowed
*/
void __rt_mutex_init(struct rt_mutex *lock, const char *name,
struct lock_class_key *key)
{
lock->owner = NULL;
raw_spin_lock_init(&lock->wait_lock);
lock->waiters = RB_ROOT_CACHED;
if (name && key)
debug_rt_mutex_init(lock, name, key);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Ingo Molnar | 38 | 69.09% | 1 | 16.67% |
| Peter Zijlstra | 9 | 16.36% | 2 | 33.33% |
| Alexander (Sasha) Levin | 6 | 10.91% | 1 | 16.67% |
| Davidlohr Bueso A | 1 | 1.82% | 1 | 16.67% |
| Thomas Gleixner | 1 | 1.82% | 1 | 16.67% |
| Total | 55 | 100.00% | 6 | 100.00% |
EXPORT_SYMBOL_GPL(__rt_mutex_init);
/**
* rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a
* proxy owner
*
* @lock: the rt_mutex to be locked
* @proxy_owner:the task to set as owner
*
* No locking. Caller has to do serializing itself
*
* Special API call for PI-futex support. This initializes the rtmutex and
* assigns it to @proxy_owner. Concurrent operations on the rtmutex are not
* possible at this point because the pi_state which contains the rtmutex
* is not yet visible to other tasks.
*/
void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
struct task_struct *proxy_owner)
{
__rt_mutex_init(lock, NULL, NULL);
debug_rt_mutex_proxy_lock(lock, proxy_owner);
rt_mutex_set_owner(lock, proxy_owner);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Ingo Molnar | 36 | 94.74% | 2 | 66.67% |
| Peter Zijlstra | 2 | 5.26% | 1 | 33.33% |
| Total | 38 | 100.00% | 3 | 100.00% |
/**
* rt_mutex_proxy_unlock - release a lock on behalf of owner
*
* @lock: the rt_mutex to be locked
*
* No locking. Caller has to do serializing itself
*
* Special API call for PI-futex support. This merrily cleans up the rtmutex
* (debugging) state. Concurrent operations on this rt_mutex are not
* possible because it belongs to the pi_state which is about to be freed
* and it is not longer visible to other tasks.
*/
void rt_mutex_proxy_unlock(struct rt_mutex *lock,
struct task_struct *proxy_owner)
{
debug_rt_mutex_proxy_unlock(lock);
rt_mutex_set_owner(lock, NULL);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Ingo Molnar | 27 | 100.00% | 1 | 100.00% |
| Total | 27 | 100.00% | 1 | 100.00% |
int __rt_mutex_start_proxy_lock(struct rt_mutex *lock,
struct rt_mutex_waiter *waiter,
struct task_struct *task)
{
int ret;
if (try_to_take_rt_mutex(lock, task, NULL))
return 1;
/* We enforce deadlock detection for futexes */
ret = task_blocks_on_rt_mutex(lock, waiter, task,
RT_MUTEX_FULL_CHAINWALK);
if (ret && !rt_mutex_owner(lock)) {
/*
* Reset the return value. We might have
* returned with -EDEADLK and the owner
* released the lock while we were walking the
* pi chain. Let the waiter sort it out.
*/
ret = 0;
}
if (unlikely(ret))
remove_waiter(lock, waiter);
debug_rt_mutex_print_deadlock(waiter);
return ret;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Darren Hart | 57 | 63.33% | 1 | 20.00% |
| Lai Jiangshan | 21 | 23.33% | 1 | 20.00% |
| Peter Zijlstra | 10 | 11.11% | 1 | 20.00% |
| Thomas Gleixner | 2 | 2.22% | 2 | 40.00% |
| Total | 90 | 100.00% | 5 | 100.00% |
/**
* rt_mutex_start_proxy_lock() - Start lock acquisition for another task
* @lock: the rt_mutex to take
* @waiter: the pre-initialized rt_mutex_waiter
* @task: the task to prepare
*
* Returns:
* 0 - task blocked on lock
* 1 - acquired the lock for task, caller should wake it up
* <0 - error
*
* Special API call for FUTEX_REQUEUE_PI support.
*/
int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
struct rt_mutex_waiter *waiter,
struct task_struct *task)
{
int ret;
raw_spin_lock_irq(&lock->wait_lock);
ret = __rt_mutex_start_proxy_lock(lock, waiter, task);
raw_spin_unlock_irq(&lock->wait_lock);
return ret;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Peter Zijlstra | 38 | 71.70% | 1 | 50.00% |
| Darren Hart | 15 | 28.30% | 1 | 50.00% |
| Total | 53 | 100.00% | 2 | 100.00% |
/**
* rt_mutex_next_owner - return the next owner of the lock
*
* @lock: the rt lock query
*
* Returns the next owner of the lock or NULL
*
* Caller has to serialize against other accessors to the lock
* itself.
*
* Special API call for PI-futex support
*/
struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock)
{
if (!rt_mutex_has_waiters(lock))
return NULL;
return rt_mutex_top_waiter(lock)->task;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Ingo Molnar | 31 | 100.00% | 1 | 100.00% |
| Total | 31 | 100.00% | 1 | 100.00% |
/**
* rt_mutex_wait_proxy_lock() - Wait for lock acquisition
* @lock: the rt_mutex we were woken on
* @to: the timeout, null if none. hrtimer should already have
* been started.
* @waiter: the pre-initialized rt_mutex_waiter
*
* Wait for the the lock acquisition started on our behalf by
* rt_mutex_start_proxy_lock(). Upon failure, the caller must call
* rt_mutex_cleanup_proxy_lock().
*
* Returns:
* 0 - success
* <0 - error, one of -EINTR, -ETIMEDOUT
*
* Special API call for PI-futex support
*/
int rt_mutex_wait_proxy_lock(struct rt_mutex *lock,
struct hrtimer_sleeper *to,
struct rt_mutex_waiter *waiter)
{
int ret;
raw_spin_lock_irq(&lock->wait_lock);
/* sleep on the mutex */
set_current_state(TASK_INTERRUPTIBLE);
ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter);
/*
* try_to_take_rt_mutex() sets the waiter bit unconditionally. We might
* have to fix that up.
*/
fixup_rt_mutex_waiters(lock);
raw_spin_unlock_irq(&lock->wait_lock);
return ret;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Darren Hart | 46 | 68.66% | 1 | 25.00% |
| Peter Zijlstra | 20 | 29.85% | 2 | 50.00% |
| Thomas Gleixner | 1 | 1.49% | 1 | 25.00% |
| Total | 67 | 100.00% | 4 | 100.00% |
/**
* rt_mutex_cleanup_proxy_lock() - Cleanup failed lock acquisition
* @lock: the rt_mutex we were woken on
* @waiter: the pre-initialized rt_mutex_waiter
*
* Attempt to clean up after a failed rt_mutex_wait_proxy_lock().
*
* Unless we acquired the lock; we're still enqueued on the wait-list and can
* in fact still be granted ownership until we're removed. Therefore we can
* find we are in fact the owner and must disregard the
* rt_mutex_wait_proxy_lock() failure.
*
* Returns:
* true - did the cleanup, we done.
* false - we acquired the lock after rt_mutex_wait_proxy_lock() returned,
* caller should disregards its return value.
*
* Special API call for PI-futex support
*/
bool rt_mutex_cleanup_proxy_lock(struct rt_mutex *lock,
struct rt_mutex_waiter *waiter)
{
bool cleanup = false;
raw_spin_lock_irq(&lock->wait_lock);
/*
* Do an unconditional try-lock, this deals with the lock stealing
* state where __rt_mutex_futex_unlock() -> mark_wakeup_next_waiter()
* sets a NULL owner.
*
* We're not interested in the return value, because the subsequent
* test on rt_mutex_owner() will infer that. If the trylock succeeded,
* we will own the lock and it will have removed the waiter. If we
* failed the trylock, we're still not owner and we need to remove
* ourselves.
*/
try_to_take_rt_mutex(lock, current, waiter);
/*
* Unless we're the owner; we're still enqueued on the wait_list.
* So check if we became owner, if not, take us off the wait_list.
*/
if (rt_mutex_owner(lock) != current) {
remove_waiter(lock, waiter);
cleanup = true;
}
/*
* try_to_take_rt_mutex() sets the waiter bit unconditionally. We might
* have to fix that up.
*/
fixup_rt_mutex_waiters(lock);
raw_spin_unlock_irq(&lock->wait_lock);
return cleanup;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Peter Zijlstra | 55 | 70.51% | 3 | 60.00% |
| Darren Hart | 22 | 28.21% | 1 | 20.00% |
| Thomas Gleixner | 1 | 1.28% | 1 | 20.00% |
| Total | 78 | 100.00% | 5 | 100.00% |
Overall Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Ingo Molnar | 1659 | 37.56% | 7 | 9.46% |
| Peter Zijlstra | 1079 | 24.43% | 14 | 18.92% |
| Thomas Gleixner | 976 | 22.10% | 24 | 32.43% |
| Darren Hart | 276 | 6.25% | 1 | 1.35% |
| Lai Jiangshan | 151 | 3.42% | 1 | 1.35% |
| Davidlohr Bueso A | 102 | 2.31% | 7 | 9.46% |
| Sebastian Andrzej Siewior | 73 | 1.65% | 5 | 6.76% |
| Xunlei Pang | 41 | 0.93% | 3 | 4.05% |
| Steven Rostedt | 28 | 0.63% | 2 | 2.70% |
| Dario Faggioli | 11 | 0.25% | 1 | 1.35% |
| Alexander (Sasha) Levin | 6 | 0.14% | 1 | 1.35% |
| Juri Lelli | 4 | 0.09% | 1 | 1.35% |
| Clark Williams | 3 | 0.07% | 1 | 1.35% |
| Pavel Emelyanov | 3 | 0.07% | 1 | 1.35% |
| Luis Henriques | 1 | 0.02% | 1 | 1.35% |
| Paul Gortmaker | 1 | 0.02% | 1 | 1.35% |
| Tom (JeHyeon) Yeon | 1 | 0.02% | 1 | 1.35% |
| Waiman Long | 1 | 0.02% | 1 | 1.35% |
| Mike Galbraith | 1 | 0.02% | 1 | 1.35% |
| Total | 4417 | 100.00% | 74 | 100.00% |
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