rtmutex: Cleanup deadlock detector debug logic
The conditions under which deadlock detection is conducted are unclear and undocumented. Add constants instead of using 0/1 and provide a selection function which hides the additional debug dependency from the calling code. Add comments where needed. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Reviewed-by: Steven Rostedt <rostedt@goodmis.org> Cc: Lai Jiangshan <laijs@cn.fujitsu.com> Link: http://lkml.kernel.org/r/20140522031949.947264874@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Thomas Gleixner
parent
c051b21f71
commit
8930ed80f9
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@ -66,12 +66,13 @@ void rt_mutex_debug_task_free(struct task_struct *task)
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* the deadlock. We print when we return. act_waiter can be NULL in
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* case of a remove waiter operation.
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*/
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void debug_rt_mutex_deadlock(int detect, struct rt_mutex_waiter *act_waiter,
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void debug_rt_mutex_deadlock(enum rtmutex_chainwalk chwalk,
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struct rt_mutex_waiter *act_waiter,
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struct rt_mutex *lock)
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{
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struct task_struct *task;
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if (!debug_locks || detect || !act_waiter)
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if (!debug_locks || chwalk == RT_MUTEX_FULL_CHAINWALK || !act_waiter)
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return;
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task = rt_mutex_owner(act_waiter->lock);
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@ -20,14 +20,15 @@ extern void debug_rt_mutex_unlock(struct rt_mutex *lock);
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extern void debug_rt_mutex_proxy_lock(struct rt_mutex *lock,
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struct task_struct *powner);
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extern void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock);
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extern void debug_rt_mutex_deadlock(int detect, struct rt_mutex_waiter *waiter,
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extern void debug_rt_mutex_deadlock(enum rtmutex_chainwalk chwalk,
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struct rt_mutex_waiter *waiter,
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struct rt_mutex *lock);
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extern void debug_rt_mutex_print_deadlock(struct rt_mutex_waiter *waiter);
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# define debug_rt_mutex_reset_waiter(w) \
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do { (w)->deadlock_lock = NULL; } while (0)
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static inline int debug_rt_mutex_detect_deadlock(struct rt_mutex_waiter *waiter,
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int detect)
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static inline bool debug_rt_mutex_detect_deadlock(struct rt_mutex_waiter *waiter,
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enum rtmutex_chainwalk walk)
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{
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return (waiter != NULL);
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}
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@ -307,6 +307,32 @@ static void rt_mutex_adjust_prio(struct task_struct *task)
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raw_spin_unlock_irqrestore(&task->pi_lock, flags);
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}
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/*
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* Deadlock detection is conditional:
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*
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* If CONFIG_DEBUG_RT_MUTEXES=n, deadlock detection is only conducted
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* if the detect argument is == RT_MUTEX_FULL_CHAINWALK.
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*
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* If CONFIG_DEBUG_RT_MUTEXES=y, deadlock detection is always
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* conducted independent of the detect argument.
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*
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* If the waiter argument is NULL this indicates the deboost path and
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* deadlock detection is disabled independent of the detect argument
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* and the config settings.
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*/
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static bool rt_mutex_cond_detect_deadlock(struct rt_mutex_waiter *waiter,
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enum rtmutex_chainwalk chwalk)
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{
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/*
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* This is just a wrapper function for the following call,
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* because debug_rt_mutex_detect_deadlock() smells like a magic
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* debug feature and I wanted to keep the cond function in the
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* main source file along with the comments instead of having
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* two of the same in the headers.
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*/
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return debug_rt_mutex_detect_deadlock(waiter, chwalk);
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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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@ -381,7 +407,7 @@ static inline struct rt_mutex *task_blocked_on_lock(struct task_struct *p)
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* goto again;
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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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enum rtmutex_chainwalk chwalk,
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struct rt_mutex *orig_lock,
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struct rt_mutex *next_lock,
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struct rt_mutex_waiter *orig_waiter,
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@ -389,12 +415,12 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task,
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{
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struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter;
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struct rt_mutex_waiter *prerequeue_top_waiter;
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int detect_deadlock, ret = 0, depth = 0;
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int ret = 0, depth = 0;
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struct rt_mutex *lock;
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bool detect_deadlock;
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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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detect_deadlock = rt_mutex_cond_detect_deadlock(orig_waiter, chwalk);
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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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@ -520,7 +546,7 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task,
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* walk, we detected a deadlock.
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*/
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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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debug_rt_mutex_deadlock(chwalk, orig_waiter, lock);
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raw_spin_unlock(&lock->wait_lock);
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ret = -EDEADLK;
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goto out_unlock_pi;
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@ -784,7 +810,7 @@ static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task,
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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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struct task_struct *task,
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int detect_deadlock)
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enum rtmutex_chainwalk chwalk)
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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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@ -830,7 +856,7 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
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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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} else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock)) {
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} else if (rt_mutex_cond_detect_deadlock(waiter, chwalk)) {
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chain_walk = 1;
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}
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@ -855,7 +881,7 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
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raw_spin_unlock(&lock->wait_lock);
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res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock,
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res = rt_mutex_adjust_prio_chain(owner, chwalk, lock,
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next_lock, waiter, task);
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raw_spin_lock(&lock->wait_lock);
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@ -960,7 +986,8 @@ static void remove_waiter(struct rt_mutex *lock,
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raw_spin_unlock(&lock->wait_lock);
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rt_mutex_adjust_prio_chain(owner, 0, lock, next_lock, NULL, current);
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rt_mutex_adjust_prio_chain(owner, RT_MUTEX_MIN_CHAINWALK, lock,
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next_lock, NULL, current);
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raw_spin_lock(&lock->wait_lock);
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}
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@ -990,7 +1017,8 @@ void rt_mutex_adjust_pi(struct task_struct *task)
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/* gets dropped in rt_mutex_adjust_prio_chain()! */
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get_task_struct(task);
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rt_mutex_adjust_prio_chain(task, 0, NULL, next_lock, NULL, task);
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rt_mutex_adjust_prio_chain(task, RT_MUTEX_MIN_CHAINWALK, NULL,
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next_lock, NULL, task);
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}
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/**
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@ -1068,7 +1096,7 @@ static void rt_mutex_handle_deadlock(int res, int detect_deadlock,
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static int __sched
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rt_mutex_slowlock(struct rt_mutex *lock, int state,
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struct hrtimer_sleeper *timeout,
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int detect_deadlock)
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enum rtmutex_chainwalk chwalk)
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{
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struct rt_mutex_waiter waiter;
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int ret = 0;
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@ -1094,7 +1122,7 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state,
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timeout->task = NULL;
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}
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ret = task_blocks_on_rt_mutex(lock, &waiter, current, detect_deadlock);
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ret = task_blocks_on_rt_mutex(lock, &waiter, current, chwalk);
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if (likely(!ret))
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ret = __rt_mutex_slowlock(lock, state, timeout, &waiter);
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@ -1103,7 +1131,7 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state,
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if (unlikely(ret)) {
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remove_waiter(lock, &waiter);
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rt_mutex_handle_deadlock(ret, detect_deadlock, &waiter);
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rt_mutex_handle_deadlock(ret, chwalk, &waiter);
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}
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/*
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@ -1230,27 +1258,29 @@ static inline int
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rt_mutex_fastlock(struct rt_mutex *lock, int state,
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int (*slowfn)(struct rt_mutex *lock, int state,
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struct hrtimer_sleeper *timeout,
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int detect_deadlock))
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enum rtmutex_chainwalk chwalk))
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{
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if (likely(rt_mutex_cmpxchg(lock, NULL, current))) {
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rt_mutex_deadlock_account_lock(lock, current);
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return 0;
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} else
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return slowfn(lock, state, NULL, 0);
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return slowfn(lock, state, NULL, RT_MUTEX_MIN_CHAINWALK);
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}
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static inline int
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rt_mutex_timed_fastlock(struct rt_mutex *lock, int state,
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struct hrtimer_sleeper *timeout, int detect_deadlock,
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struct hrtimer_sleeper *timeout,
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enum rtmutex_chainwalk chwalk,
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int (*slowfn)(struct rt_mutex *lock, int state,
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struct hrtimer_sleeper *timeout,
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int detect_deadlock))
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enum rtmutex_chainwalk chwalk))
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{
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if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
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if (chwalk == RT_MUTEX_MIN_CHAINWALK &&
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likely(rt_mutex_cmpxchg(lock, NULL, current))) {
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rt_mutex_deadlock_account_lock(lock, current);
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return 0;
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} else
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return slowfn(lock, state, timeout, detect_deadlock);
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return slowfn(lock, state, timeout, chwalk);
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}
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static inline int
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@ -1312,7 +1342,8 @@ int rt_mutex_timed_futex_lock(struct rt_mutex *lock,
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{
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might_sleep();
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return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, 1,
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return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout,
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RT_MUTEX_FULL_CHAINWALK,
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rt_mutex_slowlock);
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}
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@ -1334,7 +1365,8 @@ rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout)
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{
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might_sleep();
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return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, 0,
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return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout,
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RT_MUTEX_MIN_CHAINWALK,
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rt_mutex_slowlock);
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}
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EXPORT_SYMBOL_GPL(rt_mutex_timed_lock);
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@ -1463,7 +1495,8 @@ int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
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}
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/* We enforce deadlock detection for futexes */
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ret = task_blocks_on_rt_mutex(lock, waiter, task, 1);
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ret = task_blocks_on_rt_mutex(lock, waiter, task,
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RT_MUTEX_FULL_CHAINWALK);
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if (ret && !rt_mutex_owner(lock)) {
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/*
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@ -22,10 +22,15 @@
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#define debug_rt_mutex_init(m, n) do { } while (0)
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#define debug_rt_mutex_deadlock(d, a ,l) do { } while (0)
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#define debug_rt_mutex_print_deadlock(w) do { } while (0)
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#define debug_rt_mutex_detect_deadlock(w,d) (d)
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#define debug_rt_mutex_reset_waiter(w) do { } while (0)
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static inline void rt_mutex_print_deadlock(struct rt_mutex_waiter *w)
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{
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WARN(1, "rtmutex deadlock detected\n");
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}
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static inline bool debug_rt_mutex_detect_deadlock(struct rt_mutex_waiter *w,
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enum rtmutex_chainwalk walk)
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{
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return walk == RT_MUTEX_FULL_CHAINWALK;
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}
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@ -101,6 +101,21 @@ static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock)
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((unsigned long)lock->owner & ~RT_MUTEX_OWNER_MASKALL);
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}
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/*
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* Constants for rt mutex functions which have a selectable deadlock
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* detection.
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*
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* RT_MUTEX_MIN_CHAINWALK: Stops the lock chain walk when there are
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* no further PI adjustments to be made.
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*
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* RT_MUTEX_FULL_CHAINWALK: Invoke deadlock detection with a full
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* walk of the lock chain.
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*/
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enum rtmutex_chainwalk {
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RT_MUTEX_MIN_CHAINWALK,
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RT_MUTEX_FULL_CHAINWALK,
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};
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/*
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* PI-futex support (proxy locking functions, etc.):
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*/
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