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![Thomas Gleixner](/assets/img/avatar_default.png)
The recent PRIVATE and REQUEUE_PI changes to the futex code made it hard to read. Tidy it up. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1004 lines
26 KiB
C
1004 lines
26 KiB
C
/*
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* RT-Mutexes: simple blocking mutual exclusion locks with PI support
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*
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* started by Ingo Molnar and Thomas Gleixner.
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*
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* Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
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* Copyright (C) 2005-2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
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* Copyright (C) 2005 Kihon Technologies Inc., Steven Rostedt
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* Copyright (C) 2006 Esben Nielsen
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*
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* See Documentation/rt-mutex-design.txt for details.
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*/
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#include <linux/spinlock.h>
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#include <linux/module.h>
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#include <linux/sched.h>
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#include <linux/timer.h>
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#include "rtmutex_common.h"
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/*
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* lock->owner state tracking:
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*
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* lock->owner holds the task_struct pointer of the owner. Bit 0 and 1
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* are used to keep track of the "owner is pending" and "lock has
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* waiters" state.
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*
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* owner bit1 bit0
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* NULL 0 0 lock is free (fast acquire possible)
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* NULL 0 1 invalid state
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* NULL 1 0 Transitional State*
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* NULL 1 1 invalid state
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* taskpointer 0 0 lock is held (fast release possible)
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* taskpointer 0 1 task is pending owner
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* taskpointer 1 0 lock is held and has waiters
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* taskpointer 1 1 task is pending owner and lock has more waiters
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*
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* Pending ownership is assigned to the top (highest priority)
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* waiter of the lock, when the lock is released. The thread is woken
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* up and can now take the lock. Until the lock is taken (bit 0
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* cleared) a competing higher priority thread can steal the lock
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* which puts the woken up thread back on the waiters list.
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*
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* The fast atomic compare exchange based acquire and release is only
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* possible when bit 0 and 1 of lock->owner are 0.
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*
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* (*) There's a small time where the owner can be NULL and the
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* "lock has waiters" bit is set. This can happen when grabbing the lock.
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* To prevent a cmpxchg of the owner releasing the lock, we need to set this
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* bit before looking at the lock, hence the reason this is a transitional
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* state.
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*/
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static void
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rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner,
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unsigned long mask)
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{
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unsigned long val = (unsigned long)owner | mask;
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if (rt_mutex_has_waiters(lock))
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val |= RT_MUTEX_HAS_WAITERS;
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lock->owner = (struct task_struct *)val;
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}
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static inline void clear_rt_mutex_waiters(struct rt_mutex *lock)
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{
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lock->owner = (struct task_struct *)
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((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS);
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}
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static void fixup_rt_mutex_waiters(struct rt_mutex *lock)
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{
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if (!rt_mutex_has_waiters(lock))
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clear_rt_mutex_waiters(lock);
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}
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/*
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* We can speed up the acquire/release, if the architecture
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* supports cmpxchg and if there's no debugging state to be set up
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*/
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#if defined(__HAVE_ARCH_CMPXCHG) && !defined(CONFIG_DEBUG_RT_MUTEXES)
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# define rt_mutex_cmpxchg(l,c,n) (cmpxchg(&l->owner, c, n) == c)
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static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
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{
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unsigned long owner, *p = (unsigned long *) &lock->owner;
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do {
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owner = *p;
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} while (cmpxchg(p, owner, owner | RT_MUTEX_HAS_WAITERS) != owner);
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}
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#else
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# define rt_mutex_cmpxchg(l,c,n) (0)
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static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
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{
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lock->owner = (struct task_struct *)
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((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS);
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}
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#endif
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/*
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* Calculate task priority from the waiter list priority
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*
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* Return task->normal_prio when the waiter list is empty or when
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* the waiter is not allowed to do priority boosting
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*/
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int rt_mutex_getprio(struct task_struct *task)
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{
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if (likely(!task_has_pi_waiters(task)))
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return task->normal_prio;
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return min(task_top_pi_waiter(task)->pi_list_entry.prio,
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task->normal_prio);
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}
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/*
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* Adjust the priority of a task, after its pi_waiters got modified.
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*
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* This can be both boosting and unboosting. task->pi_lock must be held.
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*/
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static void __rt_mutex_adjust_prio(struct task_struct *task)
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{
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int prio = rt_mutex_getprio(task);
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if (task->prio != prio)
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rt_mutex_setprio(task, prio);
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}
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/*
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* Adjust task priority (undo boosting). Called from the exit path of
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* rt_mutex_slowunlock() and rt_mutex_slowlock().
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*
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* (Note: We do this outside of the protection of lock->wait_lock to
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* allow the lock to be taken while or before we readjust the priority
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* of task. We do not use the spin_xx_mutex() variants here as we are
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* outside of the debug path.)
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*/
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static void rt_mutex_adjust_prio(struct task_struct *task)
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{
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unsigned long flags;
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spin_lock_irqsave(&task->pi_lock, flags);
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__rt_mutex_adjust_prio(task);
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spin_unlock_irqrestore(&task->pi_lock, flags);
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}
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/*
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* Max number of times we'll walk the boosting chain:
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*/
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int max_lock_depth = 1024;
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/*
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* Adjust the priority chain. Also used for deadlock detection.
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* Decreases task's usage by one - may thus free the task.
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* Returns 0 or -EDEADLK.
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*/
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static int rt_mutex_adjust_prio_chain(struct task_struct *task,
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int deadlock_detect,
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struct rt_mutex *orig_lock,
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struct rt_mutex_waiter *orig_waiter,
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struct task_struct *top_task)
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{
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struct rt_mutex *lock;
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struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter;
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int detect_deadlock, ret = 0, depth = 0;
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unsigned long flags;
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detect_deadlock = debug_rt_mutex_detect_deadlock(orig_waiter,
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deadlock_detect);
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/*
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* The (de)boosting is a step by step approach with a lot of
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* pitfalls. We want this to be preemptible and we want hold a
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* maximum of two locks per step. So we have to check
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* carefully whether things change under us.
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*/
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again:
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if (++depth > max_lock_depth) {
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static int prev_max;
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/*
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* Print this only once. If the admin changes the limit,
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* print a new message when reaching the limit again.
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*/
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if (prev_max != max_lock_depth) {
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prev_max = max_lock_depth;
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printk(KERN_WARNING "Maximum lock depth %d reached "
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"task: %s (%d)\n", max_lock_depth,
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top_task->comm, top_task->pid);
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}
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put_task_struct(task);
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return deadlock_detect ? -EDEADLK : 0;
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}
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retry:
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/*
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* Task can not go away as we did a get_task() before !
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*/
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spin_lock_irqsave(&task->pi_lock, flags);
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waiter = task->pi_blocked_on;
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/*
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* Check whether the end of the boosting chain has been
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* reached or the state of the chain has changed while we
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* dropped the locks.
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*/
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if (!waiter || !waiter->task)
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goto out_unlock_pi;
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/*
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* Check the orig_waiter state. After we dropped the locks,
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* the previous owner of the lock might have released the lock
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* and made us the pending owner:
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*/
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if (orig_waiter && !orig_waiter->task)
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goto out_unlock_pi;
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/*
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* Drop out, when the task has no waiters. Note,
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* top_waiter can be NULL, when we are in the deboosting
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* mode!
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*/
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if (top_waiter && (!task_has_pi_waiters(task) ||
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top_waiter != task_top_pi_waiter(task)))
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goto out_unlock_pi;
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/*
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* When deadlock detection is off then we check, if further
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* priority adjustment is necessary.
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*/
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if (!detect_deadlock && waiter->list_entry.prio == task->prio)
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goto out_unlock_pi;
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lock = waiter->lock;
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if (!spin_trylock(&lock->wait_lock)) {
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spin_unlock_irqrestore(&task->pi_lock, flags);
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cpu_relax();
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goto retry;
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}
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/* Deadlock detection */
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if (lock == orig_lock || rt_mutex_owner(lock) == top_task) {
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debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock);
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spin_unlock(&lock->wait_lock);
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ret = deadlock_detect ? -EDEADLK : 0;
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goto out_unlock_pi;
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}
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top_waiter = rt_mutex_top_waiter(lock);
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/* Requeue the waiter */
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plist_del(&waiter->list_entry, &lock->wait_list);
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waiter->list_entry.prio = task->prio;
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plist_add(&waiter->list_entry, &lock->wait_list);
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/* Release the task */
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spin_unlock_irqrestore(&task->pi_lock, flags);
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put_task_struct(task);
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/* Grab the next task */
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task = rt_mutex_owner(lock);
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get_task_struct(task);
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spin_lock_irqsave(&task->pi_lock, flags);
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if (waiter == rt_mutex_top_waiter(lock)) {
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/* Boost the owner */
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plist_del(&top_waiter->pi_list_entry, &task->pi_waiters);
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waiter->pi_list_entry.prio = waiter->list_entry.prio;
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plist_add(&waiter->pi_list_entry, &task->pi_waiters);
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__rt_mutex_adjust_prio(task);
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} else if (top_waiter == waiter) {
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/* Deboost the owner */
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plist_del(&waiter->pi_list_entry, &task->pi_waiters);
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waiter = rt_mutex_top_waiter(lock);
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waiter->pi_list_entry.prio = waiter->list_entry.prio;
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plist_add(&waiter->pi_list_entry, &task->pi_waiters);
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__rt_mutex_adjust_prio(task);
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}
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spin_unlock_irqrestore(&task->pi_lock, flags);
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top_waiter = rt_mutex_top_waiter(lock);
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spin_unlock(&lock->wait_lock);
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if (!detect_deadlock && waiter != top_waiter)
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goto out_put_task;
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goto again;
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out_unlock_pi:
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spin_unlock_irqrestore(&task->pi_lock, flags);
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out_put_task:
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put_task_struct(task);
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return ret;
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}
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/*
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* Optimization: check if we can steal the lock from the
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* assigned pending owner [which might not have taken the
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* lock yet]:
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*/
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static inline int try_to_steal_lock(struct rt_mutex *lock)
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{
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struct task_struct *pendowner = rt_mutex_owner(lock);
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struct rt_mutex_waiter *next;
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unsigned long flags;
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if (!rt_mutex_owner_pending(lock))
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return 0;
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if (pendowner == current)
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return 1;
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spin_lock_irqsave(&pendowner->pi_lock, flags);
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if (current->prio >= pendowner->prio) {
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spin_unlock_irqrestore(&pendowner->pi_lock, flags);
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return 0;
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}
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/*
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* Check if a waiter is enqueued on the pending owners
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* pi_waiters list. Remove it and readjust pending owners
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* priority.
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*/
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if (likely(!rt_mutex_has_waiters(lock))) {
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spin_unlock_irqrestore(&pendowner->pi_lock, flags);
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return 1;
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}
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/* No chain handling, pending owner is not blocked on anything: */
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next = rt_mutex_top_waiter(lock);
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plist_del(&next->pi_list_entry, &pendowner->pi_waiters);
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__rt_mutex_adjust_prio(pendowner);
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spin_unlock_irqrestore(&pendowner->pi_lock, flags);
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/*
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* We are going to steal the lock and a waiter was
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* enqueued on the pending owners pi_waiters queue. So
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* we have to enqueue this waiter into
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* current->pi_waiters list. This covers the case,
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* where current is boosted because it holds another
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* lock and gets unboosted because the booster is
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* interrupted, so we would delay a waiter with higher
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* priority as current->normal_prio.
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*
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* Note: in the rare case of a SCHED_OTHER task changing
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* its priority and thus stealing the lock, next->task
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* might be current:
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*/
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if (likely(next->task != current)) {
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spin_lock_irqsave(¤t->pi_lock, flags);
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plist_add(&next->pi_list_entry, ¤t->pi_waiters);
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__rt_mutex_adjust_prio(current);
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spin_unlock_irqrestore(¤t->pi_lock, flags);
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}
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return 1;
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}
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/*
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* Try to take an rt-mutex
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*
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* This fails
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* - when the lock has a real owner
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* - when a different pending owner exists and has higher priority than current
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*
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* Must be called with lock->wait_lock held.
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*/
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static int try_to_take_rt_mutex(struct rt_mutex *lock)
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{
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/*
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* We have to be careful here if the atomic speedups are
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* enabled, such that, when
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* - no other waiter is on the lock
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* - the lock has been released since we did the cmpxchg
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* the lock can be released or taken while we are doing the
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* checks and marking the lock with RT_MUTEX_HAS_WAITERS.
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*
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* The atomic acquire/release aware variant of
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* mark_rt_mutex_waiters uses a cmpxchg loop. After setting
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* the WAITERS bit, the atomic release / acquire can not
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* happen anymore and lock->wait_lock protects us from the
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* non-atomic case.
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*
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* Note, that this might set lock->owner =
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* RT_MUTEX_HAS_WAITERS in the case the lock is not contended
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* any more. This is fixed up when we take the ownership.
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* This is the transitional state explained at the top of this file.
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*/
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mark_rt_mutex_waiters(lock);
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if (rt_mutex_owner(lock) && !try_to_steal_lock(lock))
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return 0;
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/* We got the lock. */
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debug_rt_mutex_lock(lock);
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rt_mutex_set_owner(lock, current, 0);
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rt_mutex_deadlock_account_lock(lock, current);
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return 1;
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}
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/*
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* Task blocks on lock.
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*
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* Prepare waiter and propagate pi chain
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*
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* This must be called with lock->wait_lock held.
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*/
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static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
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struct rt_mutex_waiter *waiter,
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int detect_deadlock)
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{
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struct task_struct *owner = rt_mutex_owner(lock);
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struct rt_mutex_waiter *top_waiter = waiter;
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unsigned long flags;
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int chain_walk = 0, res;
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spin_lock_irqsave(¤t->pi_lock, flags);
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__rt_mutex_adjust_prio(current);
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waiter->task = current;
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waiter->lock = lock;
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plist_node_init(&waiter->list_entry, current->prio);
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plist_node_init(&waiter->pi_list_entry, current->prio);
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/* Get the top priority waiter on the lock */
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if (rt_mutex_has_waiters(lock))
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top_waiter = rt_mutex_top_waiter(lock);
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plist_add(&waiter->list_entry, &lock->wait_list);
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current->pi_blocked_on = waiter;
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spin_unlock_irqrestore(¤t->pi_lock, flags);
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if (waiter == rt_mutex_top_waiter(lock)) {
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spin_lock_irqsave(&owner->pi_lock, flags);
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plist_del(&top_waiter->pi_list_entry, &owner->pi_waiters);
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plist_add(&waiter->pi_list_entry, &owner->pi_waiters);
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__rt_mutex_adjust_prio(owner);
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if (owner->pi_blocked_on)
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chain_walk = 1;
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spin_unlock_irqrestore(&owner->pi_lock, flags);
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}
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else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock))
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chain_walk = 1;
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if (!chain_walk)
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return 0;
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/*
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* The owner can't disappear while holding a lock,
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* so the owner struct is protected by wait_lock.
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* Gets dropped in rt_mutex_adjust_prio_chain()!
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*/
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get_task_struct(owner);
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spin_unlock(&lock->wait_lock);
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res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, waiter,
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current);
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spin_lock(&lock->wait_lock);
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return res;
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}
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/*
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* Wake up the next waiter on the lock.
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*
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* Remove the top waiter from the current tasks waiter list and from
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* the lock waiter list. Set it as pending owner. Then wake it up.
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*
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* Called with lock->wait_lock held.
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*/
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static void wakeup_next_waiter(struct rt_mutex *lock)
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{
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struct rt_mutex_waiter *waiter;
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struct task_struct *pendowner;
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unsigned long flags;
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spin_lock_irqsave(¤t->pi_lock, flags);
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waiter = rt_mutex_top_waiter(lock);
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plist_del(&waiter->list_entry, &lock->wait_list);
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/*
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* Remove it from current->pi_waiters. We do not adjust a
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* possible priority boost right now. We execute wakeup in the
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* boosted mode and go back to normal after releasing
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* lock->wait_lock.
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*/
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plist_del(&waiter->pi_list_entry, ¤t->pi_waiters);
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pendowner = waiter->task;
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waiter->task = NULL;
|
|
|
|
rt_mutex_set_owner(lock, pendowner, RT_MUTEX_OWNER_PENDING);
|
|
|
|
spin_unlock_irqrestore(¤t->pi_lock, flags);
|
|
|
|
/*
|
|
* Clear the pi_blocked_on variable and enqueue a possible
|
|
* waiter into the pi_waiters list of the pending owner. This
|
|
* prevents that in case the pending owner gets unboosted a
|
|
* waiter with higher priority than pending-owner->normal_prio
|
|
* is blocked on the unboosted (pending) owner.
|
|
*/
|
|
spin_lock_irqsave(&pendowner->pi_lock, flags);
|
|
|
|
WARN_ON(!pendowner->pi_blocked_on);
|
|
WARN_ON(pendowner->pi_blocked_on != waiter);
|
|
WARN_ON(pendowner->pi_blocked_on->lock != lock);
|
|
|
|
pendowner->pi_blocked_on = NULL;
|
|
|
|
if (rt_mutex_has_waiters(lock)) {
|
|
struct rt_mutex_waiter *next;
|
|
|
|
next = rt_mutex_top_waiter(lock);
|
|
plist_add(&next->pi_list_entry, &pendowner->pi_waiters);
|
|
}
|
|
spin_unlock_irqrestore(&pendowner->pi_lock, flags);
|
|
|
|
wake_up_process(pendowner);
|
|
}
|
|
|
|
/*
|
|
* Remove a waiter from a lock
|
|
*
|
|
* Must be called with lock->wait_lock held
|
|
*/
|
|
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;
|
|
|
|
spin_lock_irqsave(¤t->pi_lock, flags);
|
|
plist_del(&waiter->list_entry, &lock->wait_list);
|
|
waiter->task = NULL;
|
|
current->pi_blocked_on = NULL;
|
|
spin_unlock_irqrestore(¤t->pi_lock, flags);
|
|
|
|
if (first && owner != current) {
|
|
|
|
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;
|
|
|
|
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);
|
|
|
|
spin_unlock(&lock->wait_lock);
|
|
|
|
rt_mutex_adjust_prio_chain(owner, 0, lock, NULL, current);
|
|
|
|
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;
|
|
|
|
spin_lock_irqsave(&task->pi_lock, flags);
|
|
|
|
waiter = task->pi_blocked_on;
|
|
if (!waiter || waiter->list_entry.prio == task->prio) {
|
|
spin_unlock_irqrestore(&task->pi_lock, flags);
|
|
return;
|
|
}
|
|
|
|
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);
|
|
}
|
|
|
|
/*
|
|
* 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);
|
|
waiter.task = NULL;
|
|
|
|
spin_lock(&lock->wait_lock);
|
|
|
|
/* Try to acquire the lock again: */
|
|
if (try_to_take_rt_mutex(lock)) {
|
|
spin_unlock(&lock->wait_lock);
|
|
return 0;
|
|
}
|
|
|
|
set_current_state(state);
|
|
|
|
/* Setup the timer, when timeout != NULL */
|
|
if (unlikely(timeout))
|
|
hrtimer_start(&timeout->timer, timeout->timer.expires,
|
|
HRTIMER_MODE_ABS);
|
|
|
|
for (;;) {
|
|
/* Try to acquire the lock: */
|
|
if (try_to_take_rt_mutex(lock))
|
|
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;
|
|
}
|
|
|
|
/*
|
|
* waiter.task is NULL the first time we come here and
|
|
* when we have been woken up by the previous owner
|
|
* but the lock got stolen by a higher prio task.
|
|
*/
|
|
if (!waiter.task) {
|
|
ret = task_blocks_on_rt_mutex(lock, &waiter,
|
|
detect_deadlock);
|
|
/*
|
|
* If we got woken up by the owner then start loop
|
|
* all over without going into schedule to try
|
|
* to get the lock now:
|
|
*/
|
|
if (unlikely(!waiter.task)) {
|
|
/*
|
|
* Reset the return value. We might
|
|
* have returned with -EDEADLK and the
|
|
* owner released the lock while we
|
|
* were walking the pi chain.
|
|
*/
|
|
ret = 0;
|
|
continue;
|
|
}
|
|
if (unlikely(ret))
|
|
break;
|
|
}
|
|
|
|
spin_unlock(&lock->wait_lock);
|
|
|
|
debug_rt_mutex_print_deadlock(&waiter);
|
|
|
|
if (waiter.task)
|
|
schedule_rt_mutex(lock);
|
|
|
|
spin_lock(&lock->wait_lock);
|
|
set_current_state(state);
|
|
}
|
|
|
|
set_current_state(TASK_RUNNING);
|
|
|
|
if (unlikely(waiter.task))
|
|
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);
|
|
|
|
spin_unlock(&lock->wait_lock);
|
|
|
|
/* Remove pending timer: */
|
|
if (unlikely(timeout))
|
|
hrtimer_cancel(&timeout->timer);
|
|
|
|
/*
|
|
* Readjust priority, when we did not get the lock. We might
|
|
* have been the pending owner and boosted. Since we did not
|
|
* take the lock, the PI boost has to go.
|
|
*/
|
|
if (unlikely(ret))
|
|
rt_mutex_adjust_prio(current);
|
|
|
|
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;
|
|
|
|
spin_lock(&lock->wait_lock);
|
|
|
|
if (likely(rt_mutex_owner(lock) != current)) {
|
|
|
|
ret = try_to_take_rt_mutex(lock);
|
|
/*
|
|
* try_to_take_rt_mutex() sets the lock waiters
|
|
* bit unconditionally. Clean this up.
|
|
*/
|
|
fixup_rt_mutex_waiters(lock);
|
|
}
|
|
|
|
spin_unlock(&lock->wait_lock);
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Slow path to release a rt-mutex:
|
|
*/
|
|
static void __sched
|
|
rt_mutex_slowunlock(struct rt_mutex *lock)
|
|
{
|
|
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;
|
|
spin_unlock(&lock->wait_lock);
|
|
return;
|
|
}
|
|
|
|
wakeup_next_waiter(lock);
|
|
|
|
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_lock_interruptible_ktime - 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
|
|
* -ETIMEOUT 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;
|
|
spin_lock_init(&lock->wait_lock);
|
|
plist_head_init(&lock->wait_list, &lock->wait_lock);
|
|
|
|
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, 0);
|
|
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, 0);
|
|
rt_mutex_deadlock_account_unlock(proxy_owner);
|
|
}
|
|
|
|
/**
|
|
* 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;
|
|
}
|