![Peter Zijlstra](/assets/img/avatar_default.png)
Suggested-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/n/tip-p9ijt8div0hwldexwfm4nlhj@git.kernel.org [ Fixed build failure in kernel/rcu/tree_plugin.h. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
1061 lines
27 KiB
C
1061 lines
27 KiB
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/rt-mutex-design.txt for details.
|
|
*/
|
|
#include <linux/spinlock.h>
|
|
#include <linux/export.h>
|
|
#include <linux/sched.h>
|
|
#include <linux/sched/rt.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;
|
|
}
|
|
|
|
static inline void clear_rt_mutex_waiters(struct rt_mutex *lock)
|
|
{
|
|
lock->owner = (struct task_struct *)
|
|
((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS);
|
|
}
|
|
|
|
static void fixup_rt_mutex_waiters(struct rt_mutex *lock)
|
|
{
|
|
if (!rt_mutex_has_waiters(lock))
|
|
clear_rt_mutex_waiters(lock);
|
|
}
|
|
|
|
/*
|
|
* We can speed up the acquire/release, if the architecture
|
|
* supports cmpxchg and if there's no debugging state to be set up
|
|
*/
|
|
#if defined(__HAVE_ARCH_CMPXCHG) && !defined(CONFIG_DEBUG_RT_MUTEXES)
|
|
# define rt_mutex_cmpxchg(l,c,n) (cmpxchg(&l->owner, c, n) == c)
|
|
static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
|
|
{
|
|
unsigned long owner, *p = (unsigned long *) &lock->owner;
|
|
|
|
do {
|
|
owner = *p;
|
|
} while (cmpxchg(p, owner, owner | RT_MUTEX_HAS_WAITERS) != owner);
|
|
}
|
|
#else
|
|
# define rt_mutex_cmpxchg(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);
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* Calculate task priority from the waiter list priority
|
|
*
|
|
* Return task->normal_prio when the waiter list is empty or when
|
|
* the waiter is not allowed to do priority boosting
|
|
*/
|
|
int rt_mutex_getprio(struct task_struct *task)
|
|
{
|
|
if (likely(!task_has_pi_waiters(task)))
|
|
return task->normal_prio;
|
|
|
|
return min(task_top_pi_waiter(task)->pi_list_entry.prio,
|
|
task->normal_prio);
|
|
}
|
|
|
|
/*
|
|
* Adjust the priority of a task, after its pi_waiters got modified.
|
|
*
|
|
* This can be both boosting and unboosting. task->pi_lock must be held.
|
|
*/
|
|
static void __rt_mutex_adjust_prio(struct task_struct *task)
|
|
{
|
|
int prio = rt_mutex_getprio(task);
|
|
|
|
if (task->prio != prio)
|
|
rt_mutex_setprio(task, prio);
|
|
}
|
|
|
|
/*
|
|
* Adjust task priority (undo boosting). Called from the exit path of
|
|
* rt_mutex_slowunlock() and rt_mutex_slowlock().
|
|
*
|
|
* (Note: We do this outside of the protection of lock->wait_lock to
|
|
* allow the lock to be taken while or before we readjust the priority
|
|
* of task. We do not use the spin_xx_mutex() variants here as we are
|
|
* outside of the debug path.)
|
|
*/
|
|
static void rt_mutex_adjust_prio(struct task_struct *task)
|
|
{
|
|
unsigned long flags;
|
|
|
|
raw_spin_lock_irqsave(&task->pi_lock, flags);
|
|
__rt_mutex_adjust_prio(task);
|
|
raw_spin_unlock_irqrestore(&task->pi_lock, flags);
|
|
}
|
|
|
|
/*
|
|
* Max number of times we'll walk the boosting chain:
|
|
*/
|
|
int max_lock_depth = 1024;
|
|
|
|
/*
|
|
* 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
|
|
* @deadlock_detect: 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)
|
|
* @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.
|
|
*/
|
|
static int rt_mutex_adjust_prio_chain(struct task_struct *task,
|
|
int deadlock_detect,
|
|
struct rt_mutex *orig_lock,
|
|
struct rt_mutex_waiter *orig_waiter,
|
|
struct task_struct *top_task)
|
|
{
|
|
struct rt_mutex *lock;
|
|
struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter;
|
|
int detect_deadlock, ret = 0, depth = 0;
|
|
unsigned long flags;
|
|
|
|
detect_deadlock = debug_rt_mutex_detect_deadlock(orig_waiter,
|
|
deadlock_detect);
|
|
|
|
/*
|
|
* 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:
|
|
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 deadlock_detect ? -EDEADLK : 0;
|
|
}
|
|
retry:
|
|
/*
|
|
* Task can not go away as we did a get_task() before !
|
|
*/
|
|
raw_spin_lock_irqsave(&task->pi_lock, flags);
|
|
|
|
waiter = task->pi_blocked_on;
|
|
/*
|
|
* 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;
|
|
|
|
/*
|
|
* Drop out, when the task has no waiters. Note,
|
|
* top_waiter can be NULL, when we are in the deboosting
|
|
* mode!
|
|
*/
|
|
if (top_waiter && (!task_has_pi_waiters(task) ||
|
|
top_waiter != task_top_pi_waiter(task)))
|
|
goto out_unlock_pi;
|
|
|
|
/*
|
|
* When deadlock detection is off then we check, if further
|
|
* priority adjustment is necessary.
|
|
*/
|
|
if (!detect_deadlock && waiter->list_entry.prio == task->prio)
|
|
goto out_unlock_pi;
|
|
|
|
lock = waiter->lock;
|
|
if (!raw_spin_trylock(&lock->wait_lock)) {
|
|
raw_spin_unlock_irqrestore(&task->pi_lock, flags);
|
|
cpu_relax();
|
|
goto retry;
|
|
}
|
|
|
|
/* Deadlock detection */
|
|
if (lock == orig_lock || rt_mutex_owner(lock) == top_task) {
|
|
debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock);
|
|
raw_spin_unlock(&lock->wait_lock);
|
|
ret = deadlock_detect ? -EDEADLK : 0;
|
|
goto out_unlock_pi;
|
|
}
|
|
|
|
top_waiter = rt_mutex_top_waiter(lock);
|
|
|
|
/* Requeue the waiter */
|
|
plist_del(&waiter->list_entry, &lock->wait_list);
|
|
waiter->list_entry.prio = task->prio;
|
|
plist_add(&waiter->list_entry, &lock->wait_list);
|
|
|
|
/* Release the task */
|
|
raw_spin_unlock_irqrestore(&task->pi_lock, flags);
|
|
if (!rt_mutex_owner(lock)) {
|
|
/*
|
|
* If the requeue above changed the top waiter, then we need
|
|
* to wake the new top waiter up to try to get the lock.
|
|
*/
|
|
|
|
if (top_waiter != rt_mutex_top_waiter(lock))
|
|
wake_up_process(rt_mutex_top_waiter(lock)->task);
|
|
raw_spin_unlock(&lock->wait_lock);
|
|
goto out_put_task;
|
|
}
|
|
put_task_struct(task);
|
|
|
|
/* Grab the next task */
|
|
task = rt_mutex_owner(lock);
|
|
get_task_struct(task);
|
|
raw_spin_lock_irqsave(&task->pi_lock, flags);
|
|
|
|
if (waiter == rt_mutex_top_waiter(lock)) {
|
|
/* Boost the owner */
|
|
plist_del(&top_waiter->pi_list_entry, &task->pi_waiters);
|
|
waiter->pi_list_entry.prio = waiter->list_entry.prio;
|
|
plist_add(&waiter->pi_list_entry, &task->pi_waiters);
|
|
__rt_mutex_adjust_prio(task);
|
|
|
|
} else if (top_waiter == waiter) {
|
|
/* Deboost the owner */
|
|
plist_del(&waiter->pi_list_entry, &task->pi_waiters);
|
|
waiter = rt_mutex_top_waiter(lock);
|
|
waiter->pi_list_entry.prio = waiter->list_entry.prio;
|
|
plist_add(&waiter->pi_list_entry, &task->pi_waiters);
|
|
__rt_mutex_adjust_prio(task);
|
|
}
|
|
|
|
raw_spin_unlock_irqrestore(&task->pi_lock, flags);
|
|
|
|
top_waiter = rt_mutex_top_waiter(lock);
|
|
raw_spin_unlock(&lock->wait_lock);
|
|
|
|
if (!detect_deadlock && waiter != top_waiter)
|
|
goto out_put_task;
|
|
|
|
goto again;
|
|
|
|
out_unlock_pi:
|
|
raw_spin_unlock_irqrestore(&task->pi_lock, flags);
|
|
out_put_task:
|
|
put_task_struct(task);
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Try to take an rt-mutex
|
|
*
|
|
* Must be called with lock->wait_lock held.
|
|
*
|
|
* @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 list. (could be NULL)
|
|
*/
|
|
static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task,
|
|
struct rt_mutex_waiter *waiter)
|
|
{
|
|
/*
|
|
* We have to be careful here if the atomic speedups are
|
|
* enabled, such that, when
|
|
* - no other waiter is on the lock
|
|
* - the lock has been released since we did the cmpxchg
|
|
* the lock can be released or taken while we are doing the
|
|
* checks and marking the lock with RT_MUTEX_HAS_WAITERS.
|
|
*
|
|
* The atomic acquire/release aware variant of
|
|
* mark_rt_mutex_waiters uses a cmpxchg loop. After setting
|
|
* the WAITERS bit, the atomic release / acquire can not
|
|
* happen anymore and lock->wait_lock protects us from the
|
|
* non-atomic case.
|
|
*
|
|
* Note, that this might set lock->owner =
|
|
* RT_MUTEX_HAS_WAITERS in the case the lock is not contended
|
|
* any more. This is fixed up when we take the ownership.
|
|
* This is the transitional state explained at the top of this file.
|
|
*/
|
|
mark_rt_mutex_waiters(lock);
|
|
|
|
if (rt_mutex_owner(lock))
|
|
return 0;
|
|
|
|
/*
|
|
* It will get the lock because of one of these conditions:
|
|
* 1) there is no waiter
|
|
* 2) higher priority than waiters
|
|
* 3) it is top waiter
|
|
*/
|
|
if (rt_mutex_has_waiters(lock)) {
|
|
if (task->prio >= rt_mutex_top_waiter(lock)->list_entry.prio) {
|
|
if (!waiter || waiter != rt_mutex_top_waiter(lock))
|
|
return 0;
|
|
}
|
|
}
|
|
|
|
if (waiter || rt_mutex_has_waiters(lock)) {
|
|
unsigned long flags;
|
|
struct rt_mutex_waiter *top;
|
|
|
|
raw_spin_lock_irqsave(&task->pi_lock, flags);
|
|
|
|
/* remove the queued waiter. */
|
|
if (waiter) {
|
|
plist_del(&waiter->list_entry, &lock->wait_list);
|
|
task->pi_blocked_on = NULL;
|
|
}
|
|
|
|
/*
|
|
* We have to enqueue the top waiter(if it exists) into
|
|
* task->pi_waiters list.
|
|
*/
|
|
if (rt_mutex_has_waiters(lock)) {
|
|
top = rt_mutex_top_waiter(lock);
|
|
top->pi_list_entry.prio = top->list_entry.prio;
|
|
plist_add(&top->pi_list_entry, &task->pi_waiters);
|
|
}
|
|
raw_spin_unlock_irqrestore(&task->pi_lock, flags);
|
|
}
|
|
|
|
/* We got the lock. */
|
|
debug_rt_mutex_lock(lock);
|
|
|
|
rt_mutex_set_owner(lock, task);
|
|
|
|
rt_mutex_deadlock_account_lock(lock, task);
|
|
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* Task blocks on lock.
|
|
*
|
|
* Prepare waiter and propagate pi chain
|
|
*
|
|
* This must be called with lock->wait_lock held.
|
|
*/
|
|
static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
|
|
struct rt_mutex_waiter *waiter,
|
|
struct task_struct *task,
|
|
int detect_deadlock)
|
|
{
|
|
struct task_struct *owner = rt_mutex_owner(lock);
|
|
struct rt_mutex_waiter *top_waiter = waiter;
|
|
unsigned long flags;
|
|
int chain_walk = 0, res;
|
|
|
|
raw_spin_lock_irqsave(&task->pi_lock, flags);
|
|
__rt_mutex_adjust_prio(task);
|
|
waiter->task = task;
|
|
waiter->lock = lock;
|
|
plist_node_init(&waiter->list_entry, task->prio);
|
|
plist_node_init(&waiter->pi_list_entry, task->prio);
|
|
|
|
/* Get the top priority waiter on the lock */
|
|
if (rt_mutex_has_waiters(lock))
|
|
top_waiter = rt_mutex_top_waiter(lock);
|
|
plist_add(&waiter->list_entry, &lock->wait_list);
|
|
|
|
task->pi_blocked_on = waiter;
|
|
|
|
raw_spin_unlock_irqrestore(&task->pi_lock, flags);
|
|
|
|
if (!owner)
|
|
return 0;
|
|
|
|
if (waiter == rt_mutex_top_waiter(lock)) {
|
|
raw_spin_lock_irqsave(&owner->pi_lock, flags);
|
|
plist_del(&top_waiter->pi_list_entry, &owner->pi_waiters);
|
|
plist_add(&waiter->pi_list_entry, &owner->pi_waiters);
|
|
|
|
__rt_mutex_adjust_prio(owner);
|
|
if (owner->pi_blocked_on)
|
|
chain_walk = 1;
|
|
raw_spin_unlock_irqrestore(&owner->pi_lock, flags);
|
|
}
|
|
else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock))
|
|
chain_walk = 1;
|
|
|
|
if (!chain_walk)
|
|
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(&lock->wait_lock);
|
|
|
|
res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, waiter,
|
|
task);
|
|
|
|
raw_spin_lock(&lock->wait_lock);
|
|
|
|
return res;
|
|
}
|
|
|
|
/*
|
|
* Wake up the next waiter on the lock.
|
|
*
|
|
* Remove the top waiter from the current tasks waiter list and wake it up.
|
|
*
|
|
* Called with lock->wait_lock held.
|
|
*/
|
|
static void wakeup_next_waiter(struct rt_mutex *lock)
|
|
{
|
|
struct rt_mutex_waiter *waiter;
|
|
unsigned long flags;
|
|
|
|
raw_spin_lock_irqsave(¤t->pi_lock, flags);
|
|
|
|
waiter = rt_mutex_top_waiter(lock);
|
|
|
|
/*
|
|
* Remove it from current->pi_waiters. We do not adjust a
|
|
* possible priority boost right now. We execute wakeup in the
|
|
* boosted mode and go back to normal after releasing
|
|
* lock->wait_lock.
|
|
*/
|
|
plist_del(&waiter->pi_list_entry, ¤t->pi_waiters);
|
|
|
|
rt_mutex_set_owner(lock, NULL);
|
|
|
|
raw_spin_unlock_irqrestore(¤t->pi_lock, flags);
|
|
|
|
wake_up_process(waiter->task);
|
|
}
|
|
|
|
/*
|
|
* Remove a waiter from a lock and give up
|
|
*
|
|
* Must be called with lock->wait_lock held and
|
|
* have just failed to try_to_take_rt_mutex().
|
|
*/
|
|
static void remove_waiter(struct rt_mutex *lock,
|
|
struct rt_mutex_waiter *waiter)
|
|
{
|
|
int first = (waiter == rt_mutex_top_waiter(lock));
|
|
struct task_struct *owner = rt_mutex_owner(lock);
|
|
unsigned long flags;
|
|
int chain_walk = 0;
|
|
|
|
raw_spin_lock_irqsave(¤t->pi_lock, flags);
|
|
plist_del(&waiter->list_entry, &lock->wait_list);
|
|
current->pi_blocked_on = NULL;
|
|
raw_spin_unlock_irqrestore(¤t->pi_lock, flags);
|
|
|
|
if (!owner)
|
|
return;
|
|
|
|
if (first) {
|
|
|
|
raw_spin_lock_irqsave(&owner->pi_lock, flags);
|
|
|
|
plist_del(&waiter->pi_list_entry, &owner->pi_waiters);
|
|
|
|
if (rt_mutex_has_waiters(lock)) {
|
|
struct rt_mutex_waiter *next;
|
|
|
|
next = rt_mutex_top_waiter(lock);
|
|
plist_add(&next->pi_list_entry, &owner->pi_waiters);
|
|
}
|
|
__rt_mutex_adjust_prio(owner);
|
|
|
|
if (owner->pi_blocked_on)
|
|
chain_walk = 1;
|
|
|
|
raw_spin_unlock_irqrestore(&owner->pi_lock, flags);
|
|
}
|
|
|
|
WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
|
|
|
|
if (!chain_walk)
|
|
return;
|
|
|
|
/* gets dropped in rt_mutex_adjust_prio_chain()! */
|
|
get_task_struct(owner);
|
|
|
|
raw_spin_unlock(&lock->wait_lock);
|
|
|
|
rt_mutex_adjust_prio_chain(owner, 0, lock, NULL, current);
|
|
|
|
raw_spin_lock(&lock->wait_lock);
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
unsigned long flags;
|
|
|
|
raw_spin_lock_irqsave(&task->pi_lock, flags);
|
|
|
|
waiter = task->pi_blocked_on;
|
|
if (!waiter || waiter->list_entry.prio == task->prio) {
|
|
raw_spin_unlock_irqrestore(&task->pi_lock, flags);
|
|
return;
|
|
}
|
|
|
|
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, 0, NULL, NULL, task);
|
|
}
|
|
|
|
/**
|
|
* __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
|
|
*
|
|
* lock->wait_lock must be held by the caller.
|
|
*/
|
|
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 (unlikely(state == TASK_INTERRUPTIBLE)) {
|
|
/* Signal pending? */
|
|
if (signal_pending(current))
|
|
ret = -EINTR;
|
|
if (timeout && !timeout->task)
|
|
ret = -ETIMEDOUT;
|
|
if (ret)
|
|
break;
|
|
}
|
|
|
|
raw_spin_unlock(&lock->wait_lock);
|
|
|
|
debug_rt_mutex_print_deadlock(waiter);
|
|
|
|
schedule_rt_mutex(lock);
|
|
|
|
raw_spin_lock(&lock->wait_lock);
|
|
set_current_state(state);
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Slow path lock function:
|
|
*/
|
|
static int __sched
|
|
rt_mutex_slowlock(struct rt_mutex *lock, int state,
|
|
struct hrtimer_sleeper *timeout,
|
|
int detect_deadlock)
|
|
{
|
|
struct rt_mutex_waiter waiter;
|
|
int ret = 0;
|
|
|
|
debug_rt_mutex_init_waiter(&waiter);
|
|
|
|
raw_spin_lock(&lock->wait_lock);
|
|
|
|
/* Try to acquire the lock again: */
|
|
if (try_to_take_rt_mutex(lock, current, NULL)) {
|
|
raw_spin_unlock(&lock->wait_lock);
|
|
return 0;
|
|
}
|
|
|
|
set_current_state(state);
|
|
|
|
/* Setup the timer, when timeout != NULL */
|
|
if (unlikely(timeout)) {
|
|
hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS);
|
|
if (!hrtimer_active(&timeout->timer))
|
|
timeout->task = NULL;
|
|
}
|
|
|
|
ret = task_blocks_on_rt_mutex(lock, &waiter, current, detect_deadlock);
|
|
|
|
if (likely(!ret))
|
|
ret = __rt_mutex_slowlock(lock, state, timeout, &waiter);
|
|
|
|
set_current_state(TASK_RUNNING);
|
|
|
|
if (unlikely(ret))
|
|
remove_waiter(lock, &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(&lock->wait_lock);
|
|
|
|
/* Remove pending timer: */
|
|
if (unlikely(timeout))
|
|
hrtimer_cancel(&timeout->timer);
|
|
|
|
debug_rt_mutex_free_waiter(&waiter);
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Slow path try-lock function:
|
|
*/
|
|
static inline int
|
|
rt_mutex_slowtrylock(struct rt_mutex *lock)
|
|
{
|
|
int ret = 0;
|
|
|
|
raw_spin_lock(&lock->wait_lock);
|
|
|
|
if (likely(rt_mutex_owner(lock) != current)) {
|
|
|
|
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);
|
|
}
|
|
|
|
raw_spin_unlock(&lock->wait_lock);
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Slow path to release a rt-mutex:
|
|
*/
|
|
static void __sched
|
|
rt_mutex_slowunlock(struct rt_mutex *lock)
|
|
{
|
|
raw_spin_lock(&lock->wait_lock);
|
|
|
|
debug_rt_mutex_unlock(lock);
|
|
|
|
rt_mutex_deadlock_account_unlock(current);
|
|
|
|
if (!rt_mutex_has_waiters(lock)) {
|
|
lock->owner = NULL;
|
|
raw_spin_unlock(&lock->wait_lock);
|
|
return;
|
|
}
|
|
|
|
wakeup_next_waiter(lock);
|
|
|
|
raw_spin_unlock(&lock->wait_lock);
|
|
|
|
/* Undo pi boosting if necessary: */
|
|
rt_mutex_adjust_prio(current);
|
|
}
|
|
|
|
/*
|
|
* 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 detect_deadlock,
|
|
int (*slowfn)(struct rt_mutex *lock, int state,
|
|
struct hrtimer_sleeper *timeout,
|
|
int detect_deadlock))
|
|
{
|
|
if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
|
|
rt_mutex_deadlock_account_lock(lock, current);
|
|
return 0;
|
|
} else
|
|
return slowfn(lock, state, NULL, detect_deadlock);
|
|
}
|
|
|
|
static inline int
|
|
rt_mutex_timed_fastlock(struct rt_mutex *lock, int state,
|
|
struct hrtimer_sleeper *timeout, int detect_deadlock,
|
|
int (*slowfn)(struct rt_mutex *lock, int state,
|
|
struct hrtimer_sleeper *timeout,
|
|
int detect_deadlock))
|
|
{
|
|
if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
|
|
rt_mutex_deadlock_account_lock(lock, current);
|
|
return 0;
|
|
} else
|
|
return slowfn(lock, state, timeout, detect_deadlock);
|
|
}
|
|
|
|
static inline int
|
|
rt_mutex_fasttrylock(struct rt_mutex *lock,
|
|
int (*slowfn)(struct rt_mutex *lock))
|
|
{
|
|
if (likely(rt_mutex_cmpxchg(lock, NULL, current))) {
|
|
rt_mutex_deadlock_account_lock(lock, current);
|
|
return 1;
|
|
}
|
|
return slowfn(lock);
|
|
}
|
|
|
|
static inline void
|
|
rt_mutex_fastunlock(struct rt_mutex *lock,
|
|
void (*slowfn)(struct rt_mutex *lock))
|
|
{
|
|
if (likely(rt_mutex_cmpxchg(lock, current, NULL)))
|
|
rt_mutex_deadlock_account_unlock(current);
|
|
else
|
|
slowfn(lock);
|
|
}
|
|
|
|
/**
|
|
* 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();
|
|
|
|
rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, 0, rt_mutex_slowlock);
|
|
}
|
|
EXPORT_SYMBOL_GPL(rt_mutex_lock);
|
|
|
|
/**
|
|
* rt_mutex_lock_interruptible - lock a rt_mutex interruptible
|
|
*
|
|
* @lock: the rt_mutex to be locked
|
|
* @detect_deadlock: deadlock detection on/off
|
|
*
|
|
* Returns:
|
|
* 0 on success
|
|
* -EINTR when interrupted by a signal
|
|
* -EDEADLK when the lock would deadlock (when deadlock detection is on)
|
|
*/
|
|
int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock,
|
|
int detect_deadlock)
|
|
{
|
|
might_sleep();
|
|
|
|
return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE,
|
|
detect_deadlock, rt_mutex_slowlock);
|
|
}
|
|
EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible);
|
|
|
|
/**
|
|
* 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)
|
|
* @detect_deadlock: deadlock detection on/off
|
|
*
|
|
* Returns:
|
|
* 0 on success
|
|
* -EINTR when interrupted by a signal
|
|
* -ETIMEDOUT when the timeout expired
|
|
* -EDEADLK when the lock would deadlock (when deadlock detection is on)
|
|
*/
|
|
int
|
|
rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout,
|
|
int detect_deadlock)
|
|
{
|
|
might_sleep();
|
|
|
|
return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout,
|
|
detect_deadlock, rt_mutex_slowlock);
|
|
}
|
|
EXPORT_SYMBOL_GPL(rt_mutex_timed_lock);
|
|
|
|
/**
|
|
* rt_mutex_trylock - try to lock a rt_mutex
|
|
*
|
|
* @lock: the rt_mutex to be locked
|
|
*
|
|
* Returns 1 on success and 0 on contention
|
|
*/
|
|
int __sched rt_mutex_trylock(struct rt_mutex *lock)
|
|
{
|
|
return rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock);
|
|
}
|
|
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)
|
|
{
|
|
rt_mutex_fastunlock(lock, rt_mutex_slowunlock);
|
|
}
|
|
EXPORT_SYMBOL_GPL(rt_mutex_unlock);
|
|
|
|
/**
|
|
* 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
|
|
}
|
|
|
|
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)
|
|
{
|
|
lock->owner = NULL;
|
|
raw_spin_lock_init(&lock->wait_lock);
|
|
plist_head_init(&lock->wait_list);
|
|
|
|
debug_rt_mutex_init(lock, name);
|
|
}
|
|
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
|
|
*/
|
|
void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
|
|
struct task_struct *proxy_owner)
|
|
{
|
|
__rt_mutex_init(lock, NULL);
|
|
debug_rt_mutex_proxy_lock(lock, proxy_owner);
|
|
rt_mutex_set_owner(lock, proxy_owner);
|
|
rt_mutex_deadlock_account_lock(lock, proxy_owner);
|
|
}
|
|
|
|
/**
|
|
* 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
|
|
*/
|
|
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);
|
|
rt_mutex_deadlock_account_unlock(proxy_owner);
|
|
}
|
|
|
|
/**
|
|
* 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
|
|
* @detect_deadlock: perform deadlock detection (1) or not (0)
|
|
*
|
|
* 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 detect_deadlock)
|
|
{
|
|
int ret;
|
|
|
|
raw_spin_lock(&lock->wait_lock);
|
|
|
|
if (try_to_take_rt_mutex(lock, task, NULL)) {
|
|
raw_spin_unlock(&lock->wait_lock);
|
|
return 1;
|
|
}
|
|
|
|
ret = task_blocks_on_rt_mutex(lock, waiter, task, detect_deadlock);
|
|
|
|
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);
|
|
|
|
raw_spin_unlock(&lock->wait_lock);
|
|
|
|
debug_rt_mutex_print_deadlock(waiter);
|
|
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* 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;
|
|
}
|
|
|
|
/**
|
|
* rt_mutex_finish_proxy_lock() - Complete 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
|
|
* @detect_deadlock: perform deadlock detection (1) or not (0)
|
|
*
|
|
* Complete the lock acquisition started our behalf by another thread.
|
|
*
|
|
* Returns:
|
|
* 0 - success
|
|
* <0 - error, one of -EINTR, -ETIMEDOUT, or -EDEADLK
|
|
*
|
|
* Special API call for PI-futex requeue support
|
|
*/
|
|
int rt_mutex_finish_proxy_lock(struct rt_mutex *lock,
|
|
struct hrtimer_sleeper *to,
|
|
struct rt_mutex_waiter *waiter,
|
|
int detect_deadlock)
|
|
{
|
|
int ret;
|
|
|
|
raw_spin_lock(&lock->wait_lock);
|
|
|
|
set_current_state(TASK_INTERRUPTIBLE);
|
|
|
|
ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter);
|
|
|
|
set_current_state(TASK_RUNNING);
|
|
|
|
if (unlikely(ret))
|
|
remove_waiter(lock, 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(&lock->wait_lock);
|
|
|
|
return ret;
|
|
}
|