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bd197234b0
This reverts commit d0aa7a70bf.
It not only introduced user space visible changes to the futex syscall,
it is also non-functional and there is no way to fix it proper before
the 2.6.22 release.
The breakage report ( http://lkml.org/lkml/2007/5/12/17 ) went
unanswered, and unfortunately it turned out that the concept is not
feasible at all. It violates the rtmutex semantics badly by introducing
a virtual owner, which hacks around the coupling of the user-space
pi_futex and the kernel internal rt_mutex representation.
At the moment the only safe option is to remove it fully as it contains
user-space visible changes to broken kernel code, which we do not want
to expose in the 2.6.22 release.
The patch reverts the original patch mostly 1:1, but contains a couple
of trivial manual cleanups which were necessary due to patches, which
touched the same area of code later.
Verified against the glibc tests and my own PI futex tests.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Ulrich Drepper <drepper@redhat.com>
Cc: Pierre Peiffer <pierre.peiffer@bull.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
124 lines
3.2 KiB
C
124 lines
3.2 KiB
C
/*
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* RT Mutexes: 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) 2006, Timesys Corp., Thomas Gleixner <tglx@timesys.com>
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*
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* This file contains the private data structure and API definitions.
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*/
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#ifndef __KERNEL_RTMUTEX_COMMON_H
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#define __KERNEL_RTMUTEX_COMMON_H
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#include <linux/rtmutex.h>
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/*
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* The rtmutex in kernel tester is independent of rtmutex debugging. We
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* call schedule_rt_mutex_test() instead of schedule() for the tasks which
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* belong to the tester. That way we can delay the wakeup path of those
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* threads to provoke lock stealing and testing of complex boosting scenarios.
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*/
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#ifdef CONFIG_RT_MUTEX_TESTER
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extern void schedule_rt_mutex_test(struct rt_mutex *lock);
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#define schedule_rt_mutex(_lock) \
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do { \
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if (!(current->flags & PF_MUTEX_TESTER)) \
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schedule(); \
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else \
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schedule_rt_mutex_test(_lock); \
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} while (0)
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#else
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# define schedule_rt_mutex(_lock) schedule()
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#endif
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/*
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* This is the control structure for tasks blocked on a rt_mutex,
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* which is allocated on the kernel stack on of the blocked task.
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*
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* @list_entry: pi node to enqueue into the mutex waiters list
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* @pi_list_entry: pi node to enqueue into the mutex owner waiters list
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* @task: task reference to the blocked task
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*/
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struct rt_mutex_waiter {
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struct plist_node list_entry;
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struct plist_node pi_list_entry;
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struct task_struct *task;
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struct rt_mutex *lock;
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#ifdef CONFIG_DEBUG_RT_MUTEXES
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unsigned long ip;
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pid_t deadlock_task_pid;
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struct rt_mutex *deadlock_lock;
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#endif
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};
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/*
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* Various helpers to access the waiters-plist:
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*/
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static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
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{
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return !plist_head_empty(&lock->wait_list);
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}
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static inline struct rt_mutex_waiter *
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rt_mutex_top_waiter(struct rt_mutex *lock)
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{
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struct rt_mutex_waiter *w;
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w = plist_first_entry(&lock->wait_list, struct rt_mutex_waiter,
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list_entry);
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BUG_ON(w->lock != lock);
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return w;
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}
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static inline int task_has_pi_waiters(struct task_struct *p)
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{
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return !plist_head_empty(&p->pi_waiters);
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}
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static inline struct rt_mutex_waiter *
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task_top_pi_waiter(struct task_struct *p)
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{
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return plist_first_entry(&p->pi_waiters, struct rt_mutex_waiter,
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pi_list_entry);
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}
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/*
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* lock->owner state tracking:
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*/
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#define RT_MUTEX_OWNER_PENDING 1UL
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#define RT_MUTEX_HAS_WAITERS 2UL
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#define RT_MUTEX_OWNER_MASKALL 3UL
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static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock)
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{
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return (struct task_struct *)
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((unsigned long)lock->owner & ~RT_MUTEX_OWNER_MASKALL);
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}
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static inline struct task_struct *rt_mutex_real_owner(struct rt_mutex *lock)
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{
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return (struct task_struct *)
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((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS);
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}
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static inline unsigned long rt_mutex_owner_pending(struct rt_mutex *lock)
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{
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return (unsigned long)lock->owner & RT_MUTEX_OWNER_PENDING;
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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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extern struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock);
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extern void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
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struct task_struct *proxy_owner);
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extern void rt_mutex_proxy_unlock(struct rt_mutex *lock,
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struct task_struct *proxy_owner);
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#endif
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