From: Ingo Molnar <[email protected]>
core functions for the rt-mutex subsystem.
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Arjan van de Ven <[email protected]>
----
include/linux/init_task.h | 1
include/linux/rtmutex.h | 106 ++++
include/linux/rtmutex_internal.h | 157 ++++++
include/linux/sched.h | 11
init/Kconfig | 5
kernel/Makefile | 1
kernel/fork.c | 3
kernel/rtmutex.c | 941 +++++++++++++++++++++++++++++++++++++++
kernel/rtmutex.h | 28 +
9 files changed, 1253 insertions(+)
Index: linux-pi-futex.mm.q/include/linux/init_task.h
===================================================================
--- linux-pi-futex.mm.q.orig/include/linux/init_task.h
+++ linux-pi-futex.mm.q/include/linux/init_task.h
@@ -123,6 +123,7 @@ extern struct group_info init_groups;
.journal_info = NULL, \
.cpu_timers = INIT_CPU_TIMERS(tsk.cpu_timers), \
.fs_excl = ATOMIC_INIT(0), \
+ INIT_RT_MUTEXES(tsk) \
}
Index: linux-pi-futex.mm.q/include/linux/rtmutex.h
===================================================================
--- /dev/null
+++ linux-pi-futex.mm.q/include/linux/rtmutex.h
@@ -0,0 +1,106 @@
+/*
+ * RT Mutexes: blocking mutual exclusion locks with PI support
+ *
+ * started by Ingo Molnar and Thomas Gleixner:
+ *
+ * Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <[email protected]>
+ * Copyright (C) 2006, Timesys Corp., Thomas Gleixner <[email protected]>
+ *
+ * This file contains the public data structure and API definitions.
+ */
+
+#ifndef __LINUX_RT_MUTEX_H
+#define __LINUX_RT_MUTEX_H
+
+#include <linux/linkage.h>
+#include <linux/plist.h>
+#include <linux/spinlock_types.h>
+
+/*
+ * The rt_mutex structure
+ *
+ * @wait_lock: spinlock to protect the structure
+ * @wait_list: pilist head to enqueue waiters in priority order
+ * @owner: the mutex owner
+ */
+struct rt_mutex {
+ spinlock_t wait_lock;
+ struct plist_head wait_list;
+ struct task_struct *owner;
+# ifdef CONFIG_DEBUG_RT_MUTEXES
+ int save_state;
+ struct list_head held_list;
+ unsigned long acquire_ip;
+ const char *name, *file;
+ int line;
+ void *magic;
+# endif
+};
+
+struct rt_mutex_waiter;
+struct hrtimer_sleeper;
+
+#ifdef CONFIG_DEBUG_RT_MUTEXES
+# define __DEBUG_RT_MUTEX_INITIALIZER(mutexname) \
+ , .name = #mutexname, .file = __FILE__, .line = __LINE__
+# define rt_mutex_init(mutex) __rt_mutex_init(mutex, __FUNCTION__)
+ extern void rt_mutex_debug_task_free(struct task_struct *tsk);
+#else
+# define __DEBUG_RT_MUTEX_INITIALIZER(mutexname)
+# define rt_mutex_init(mutex) __rt_mutex_init(mutex, NULL)
+# define rt_mutex_debug_task_free(t) do { } while (0)
+#endif
+
+#define __RT_MUTEX_INITIALIZER(mutexname) \
+ { .wait_lock = SPIN_LOCK_UNLOCKED \
+ , .wait_list = PLIST_HEAD_INIT(mutexname.wait_list) \
+ , .owner = NULL \
+ __DEBUG_RT_MUTEX_INITIALIZER(mutexname)}
+
+#define DEFINE_RT_MUTEX(mutexname) \
+ struct rt_mutex mutexname = __RT_MUTEX_INITIALIZER(mutexname)
+
+/***
+ * rt_mutex_is_locked - is the mutex locked
+ * @lock: the mutex to be queried
+ *
+ * Returns 1 if the mutex is locked, 0 if unlocked.
+ */
+static inline int fastcall rt_mutex_is_locked(struct rt_mutex *lock)
+{
+ return lock->owner != NULL;
+}
+
+extern void fastcall __rt_mutex_init(struct rt_mutex *lock, const char *name);
+extern void fastcall rt_mutex_destroy(struct rt_mutex *lock);
+
+extern void fastcall rt_mutex_lock(struct rt_mutex *lock);
+extern int fastcall rt_mutex_lock_interruptible(struct rt_mutex *lock,
+ int detect_deadlock);
+extern int fastcall rt_mutex_timed_lock(struct rt_mutex *lock,
+ struct hrtimer_sleeper *timeout,
+ int detect_deadlock);
+
+extern int fastcall rt_mutex_trylock(struct rt_mutex *lock);
+
+extern void fastcall rt_mutex_unlock(struct rt_mutex *lock);
+
+#ifdef CONFIG_RT_MUTEXES
+# define rt_mutex_init_task(p) \
+ do { \
+ spin_lock_init(&p->pi_lock); \
+ plist_head_init(&p->pi_waiters); \
+ p->pi_blocked_on = NULL; \
+ p->pi_locked_by = NULL; \
+ INIT_LIST_HEAD(&p->pi_lock_chain); \
+ } while (0)
+# define INIT_RT_MUTEXES(tsk) \
+ .pi_waiters = PLIST_HEAD_INIT(tsk.pi_waiters), \
+ .pi_lock = SPIN_LOCK_UNLOCKED, \
+ .pi_lock_chain = LIST_HEAD_INIT(tsk.pi_lock_chain),
+#else
+# define rt_mutex_init_task(p) do { } while (0)
+# define INIT_RT_MUTEXES(tsk)
+#endif
+
+#endif
Index: linux-pi-futex.mm.q/include/linux/rtmutex_internal.h
===================================================================
--- /dev/null
+++ linux-pi-futex.mm.q/include/linux/rtmutex_internal.h
@@ -0,0 +1,157 @@
+/*
+ * RT Mutexes: blocking mutual exclusion locks with PI support
+ *
+ * started by Ingo Molnar and Thomas Gleixner:
+ *
+ * Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <[email protected]>
+ * Copyright (C) 2006, Timesys Corp., Thomas Gleixner <[email protected]>
+ *
+ * This file contains the private data structure and API definitions.
+ */
+
+#ifndef __LINUX_RT_MUTEX_INTERNAL_H
+#define __LINUX_RT_MUTEX_INTERNAL_H
+
+#include <linux/rtmutex.h>
+
+/*
+ * This is the control structure for tasks blocked on a rt_mutex,
+ * which is allocated on the kernel stack on of the blocked task.
+ *
+ * @list_entry: pi node to enqueue into the mutex waiters list
+ * @pi_list_entry: pi node to enqueue into the mutex owner waiters list
+ * @task: task reference to the blocked task
+ */
+struct rt_mutex_waiter {
+ struct plist_node list_entry;
+ struct plist_node pi_list_entry;
+ struct task_struct *task;
+ struct rt_mutex *lock;
+#ifdef CONFIG_DEBUG_RT_MUTEXES
+ unsigned long ip;
+ pid_t deadlock_task_pid;
+ struct rt_mutex *deadlock_lock;
+#endif
+};
+
+/*
+ * Plist wrapper macros
+ */
+#define rt_mutex_has_waiters(lock) (!plist_head_empty(&lock->wait_list))
+
+#define rt_mutex_top_waiter(lock) \
+({ struct rt_mutex_waiter *__w = plist_first_entry(&lock->wait_list, \
+ struct rt_mutex_waiter, list_entry); \
+ BUG_ON(__w->lock != lock); \
+ __w; \
+})
+
+#define task_has_pi_waiters(task) (!plist_head_empty(&task->pi_waiters))
+
+#define task_top_pi_waiter(task) \
+ plist_first_entry(&task->pi_waiters, struct rt_mutex_waiter, pi_list_entry)
+
+/*
+ * lock->owner state tracking:
+ *
+ * lock->owner holds the task_struct pointer of the owner. Bit 0 and 1
+ * are used to keep track of the "owner is pending" and "lock has
+ * waiters" state.
+ *
+ * owner bit1 bit0
+ * NULL 0 0 lock is free (fast acquire possible)
+ * NULL 0 1 invalid state
+ * NULL 1 0 invalid state
+ * NULL 1 1 invalid state
+ * taskpointer 0 0 lock is held (fast release possible)
+ * taskpointer 0 1 task is pending owner
+ * taskpointer 1 0 lock is held and has waiters
+ * taskpointer 1 1 task is pending owner and lock has more waiters
+ *
+ * Pending ownership is assigned to the top (highest priority)
+ * waiter of the lock, when the lock is released. The thread is woken
+ * up and can now take the lock. Until the lock is taken (bit 0
+ * cleared) a competing higher priority thread can steal the lock
+ * which puts the woken up thread back on the waiters list.
+ *
+ * The fast atomic compare exchange based acquire and release is only
+ * possible when bit 0 and 1 of lock->owner are 0.
+ */
+#define RT_MUTEX_OWNER_PENDING 1UL
+#define RT_MUTEX_HAS_WAITERS 2UL
+#define RT_MUTEX_OWNER_MASKALL 3UL
+
+#define rt_mutex_owner(lock) \
+({ \
+ typecheck(struct rt_mutex *,(lock)); \
+ ((struct task_struct *)((unsigned long)((lock)->owner) & ~RT_MUTEX_OWNER_MASKALL)); \
+})
+
+#define rt_mutex_real_owner(lock) \
+({ \
+ typecheck(struct rt_mutex *,(lock)); \
+ ((struct task_struct *)((unsigned long)((lock)->owner) & ~RT_MUTEX_HAS_WAITERS)); \
+})
+
+#define rt_mutex_owner_pending(lock) \
+({ \
+ typecheck(struct rt_mutex *,(lock)); \
+ ((unsigned long)((lock)->owner) & RT_MUTEX_OWNER_PENDING); \
+})
+
+static inline void rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner,
+ unsigned long msk)
+{
+ unsigned long val = ((unsigned long) owner) | msk;
+
+ 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)
+{
+ unsigned long owner;
+
+ owner = ((unsigned long) lock->owner) & ~RT_MUTEX_HAS_WAITERS;
+ lock->owner = (struct task_struct *)(owner);
+}
+
+static inline 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)
+{
+ unsigned long owner = ((unsigned long) lock->owner)| RT_MUTEX_HAS_WAITERS;
+
+ lock->owner = (struct task_struct *) owner;
+}
+
+#endif
+
+#endif
Index: linux-pi-futex.mm.q/include/linux/sched.h
===================================================================
--- linux-pi-futex.mm.q.orig/include/linux/sched.h
+++ linux-pi-futex.mm.q/include/linux/sched.h
@@ -36,6 +36,7 @@
#include <linux/seccomp.h>
#include <linux/rcupdate.h>
#include <linux/futex.h>
+#include <linux/rtmutex.h>
#include <linux/auxvec.h> /* For AT_VECTOR_SIZE */
@@ -858,6 +859,16 @@ struct task_struct {
/* Protection of the PI data structures: */
spinlock_t pi_lock;
+#ifdef CONFIG_RT_MUTEXES
+ /* PI waiters blocked on a rt_mutex held by this task */
+ struct plist_head pi_waiters;
+ /* Deadlock detection and priority inheritance handling */
+ struct rt_mutex_waiter *pi_blocked_on;
+ /* PI locking helpers */
+ struct task_struct *pi_locked_by;
+ struct list_head pi_lock_chain;
+#endif
+
#ifdef CONFIG_DEBUG_MUTEXES
/* mutex deadlock detection */
struct mutex_waiter *blocked_on;
Index: linux-pi-futex.mm.q/init/Kconfig
===================================================================
--- linux-pi-futex.mm.q.orig/init/Kconfig
+++ linux-pi-futex.mm.q/init/Kconfig
@@ -361,9 +361,14 @@ config BASE_FULL
kernel data structures. This saves memory on small machines,
but may reduce performance.
+config RT_MUTEXES
+ boolean
+ select PLIST
+
config FUTEX
bool "Enable futex support" if EMBEDDED
default y
+ select RT_MUTEXES
help
Disabling this option will cause the kernel to be built without
support for "fast userspace mutexes". The resulting kernel may not
Index: linux-pi-futex.mm.q/kernel/Makefile
===================================================================
--- linux-pi-futex.mm.q.orig/kernel/Makefile
+++ linux-pi-futex.mm.q/kernel/Makefile
@@ -16,6 +16,7 @@ obj-$(CONFIG_FUTEX) += futex.o
ifeq ($(CONFIG_COMPAT),y)
obj-$(CONFIG_FUTEX) += futex_compat.o
endif
+obj-$(CONFIG_RT_MUTEXES) += rtmutex.o
obj-$(CONFIG_GENERIC_ISA_DMA) += dma.o
obj-$(CONFIG_SMP) += cpu.o spinlock.o
obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock.o
Index: linux-pi-futex.mm.q/kernel/fork.c
===================================================================
--- linux-pi-futex.mm.q.orig/kernel/fork.c
+++ linux-pi-futex.mm.q/kernel/fork.c
@@ -104,6 +104,7 @@ static kmem_cache_t *mm_cachep;
void free_task(struct task_struct *tsk)
{
free_thread_info(tsk->thread_info);
+ rt_mutex_debug_task_free(tsk);
free_task_struct(tsk);
}
EXPORT_SYMBOL(free_task);
@@ -1042,6 +1043,8 @@ static task_t *copy_process(unsigned lon
mpol_fix_fork_child_flag(p);
#endif
+ rt_mutex_init_task(p);
+
#ifdef CONFIG_DEBUG_MUTEXES
p->blocked_on = NULL; /* not blocked yet */
#endif
Index: linux-pi-futex.mm.q/kernel/rtmutex.c
===================================================================
--- /dev/null
+++ linux-pi-futex.mm.q/kernel/rtmutex.c
@@ -0,0 +1,941 @@
+/*
+ * 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 <[email protected]>
+ * Copyright (C) 2006 Timesys Corp., Thomas Gleixner <[email protected]>
+ * Copyright (C) 2005 Kihon Technologies Inc., Steven Rostedt
+ */
+#include <linux/spinlock.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/timer.h>
+
+#include <linux/rtmutex_internal.h>
+
+#ifdef CONFIG_DEBUG_RT_MUTEXES
+# include "rtmutex-debug.h"
+#else
+# include "rtmutex.h"
+#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;
+
+ spin_lock_irqsave(&task->pi_lock, flags);
+ __rt_mutex_adjust_prio(task);
+ spin_unlock_irqrestore(&task->pi_lock, flags);
+}
+
+/*
+ * PI-locking: we lock PI-dependencies opportunistically via trylock.
+ *
+ * In the overwhelming majority of cases the 'PI chain' is empty or at
+ * most 1-2 entries long, for which the trylock is sufficient,
+ * scalability-wise. The locking might look a bit scary, for which we
+ * apologize in advance :-)
+ *
+ * If any of the trylocks fails then we back out, task the global
+ * pi_conflicts_lock and take the locks again. This ensures deadlock-free
+ * but still scalable locking in the dependency graph, combined with
+ * the ability to reliably (and cheaply) detect user-space deadlocks.
+ */
+static DEFINE_SPINLOCK(pi_conflicts_lock);
+
+/*
+ * Lock the full boosting chain.
+ *
+ * If 'try' is set, we have to backout if we hit a owner who is
+ * running its own pi chain operation. We go back and take the slow
+ * path via the pi_conflicts_lock.
+ */
+static int lock_pi_chain(struct rt_mutex *act_lock,
+ struct rt_mutex_waiter *waiter,
+ struct list_head *lock_chain,
+ int try, int detect_deadlock)
+{
+ struct task_struct *owner;
+ struct rt_mutex *nextlock, *lock = act_lock;
+ struct rt_mutex_waiter *nextwaiter;
+
+ /*
+ * Debugging might turn deadlock detection on, unconditionally:
+ */
+ detect_deadlock = debug_rt_mutex_detect_deadlock(detect_deadlock);
+
+ for (;;) {
+ owner = rt_mutex_owner(lock);
+
+ /* Check for circular dependencies */
+ if (unlikely(owner->pi_locked_by == current)) {
+ debug_rt_mutex_deadlock(detect_deadlock, waiter, lock);
+ return detect_deadlock ? -EDEADLK : 0;
+ }
+
+ while (!spin_trylock(&owner->pi_lock)) {
+ /*
+ * Owner runs its own chain. Go back and take
+ * the slow path
+ */
+ if (try && owner->pi_locked_by == owner)
+ return -EBUSY;
+ cpu_relax();
+ }
+
+ BUG_ON(owner->pi_locked_by);
+ owner->pi_locked_by = current;
+ BUG_ON(!list_empty(&owner->pi_lock_chain));
+ list_add(&owner->pi_lock_chain, lock_chain);
+
+ /*
+ * When the owner is blocked on a lock, try to take
+ * the lock:
+ */
+ nextwaiter = owner->pi_blocked_on;
+
+ /* End of chain? */
+ if (!nextwaiter)
+ return 0;
+
+ nextlock = nextwaiter->lock;
+
+ /* Check for circular dependencies: */
+ if (unlikely(nextlock == act_lock ||
+ rt_mutex_owner(nextlock) == current)) {
+ debug_rt_mutex_deadlock(detect_deadlock, waiter,
+ nextlock);
+ list_del_init(&owner->pi_lock_chain);
+ owner->pi_locked_by = NULL;
+ spin_unlock(&owner->pi_lock);
+ return detect_deadlock ? -EDEADLK : 0;
+ }
+
+ /* Try to get nextlock->wait_lock: */
+ if (unlikely(!spin_trylock(&nextlock->wait_lock))) {
+ list_del_init(&owner->pi_lock_chain);
+ owner->pi_locked_by = NULL;
+ spin_unlock(&owner->pi_lock);
+ cpu_relax();
+ continue;
+ }
+
+ lock = nextlock;
+
+ /*
+ * If deadlock detection is done (or has to be done, as
+ * for userspace locks), we have to walk the full chain
+ * unconditionally.
+ */
+ if (detect_deadlock)
+ continue;
+
+ /*
+ * Optimization: we only have to continue up to the point
+ * where boosting/unboosting still has to be done:
+ */
+
+ /* Boost or unboost? */
+ if (waiter) {
+ /* If the top waiter has higher priority, stop: */
+ if (rt_mutex_top_waiter(lock)->list_entry.prio <=
+ waiter->list_entry.prio)
+ return 0;
+ } else {
+ /* If nextwaiter is not the top waiter, stop: */
+ if (rt_mutex_top_waiter(lock) != nextwaiter)
+ return 0;
+ }
+ }
+}
+
+/*
+ * Unlock the pi_chain:
+ */
+static void unlock_pi_chain(struct list_head *lock_chain)
+{
+ struct task_struct *owner, *tmp;
+
+ list_for_each_entry_safe(owner, tmp, lock_chain, pi_lock_chain) {
+ struct rt_mutex_waiter *waiter = owner->pi_blocked_on;
+
+ list_del_init(&owner->pi_lock_chain);
+ BUG_ON(!owner->pi_locked_by);
+ owner->pi_locked_by = NULL;
+ if (waiter)
+ spin_unlock(&waiter->lock->wait_lock);
+ spin_unlock(&owner->pi_lock);
+ }
+}
+
+/*
+ * Do the priority (un)boosting along the chain:
+ */
+static void adjust_pi_chain(struct rt_mutex *lock,
+ struct rt_mutex_waiter *waiter,
+ struct rt_mutex_waiter *top_waiter,
+ struct list_head *lock_chain)
+{
+ struct task_struct *owner = rt_mutex_owner(lock);
+ struct list_head *curr = lock_chain->prev;
+
+ for (;;) {
+ if (top_waiter)
+ plist_del(&top_waiter->pi_list_entry,
+ &owner->pi_waiters);
+
+ if (waiter && waiter == rt_mutex_top_waiter(lock)) {
+ waiter->pi_list_entry.prio = waiter->task->prio;
+ plist_add(&waiter->pi_list_entry, &owner->pi_waiters);
+ }
+ __rt_mutex_adjust_prio(owner);
+
+ waiter = owner->pi_blocked_on;
+ if (!waiter || curr->prev == lock_chain)
+ return;
+
+ curr = curr->prev;
+ lock = waiter->lock;
+ owner = rt_mutex_owner(lock);
+ top_waiter = rt_mutex_top_waiter(lock);
+
+ plist_del(&waiter->list_entry, &lock->wait_list);
+ waiter->list_entry.prio = waiter->task->prio;
+ plist_add(&waiter->list_entry, &lock->wait_list);
+
+ /*
+ * We can stop here, if the waiter is/was not the top
+ * priority waiter:
+ */
+ if (top_waiter != waiter &&
+ waiter != rt_mutex_top_waiter(lock))
+ return;
+
+ /*
+ * Note: waiter is not necessarily the new top
+ * waiter!
+ */
+ waiter = rt_mutex_top_waiter(lock);
+ }
+}
+
+/*
+ * Task blocks on lock.
+ *
+ * Prepare waiter and potentially propagate our priority into the 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,
+ int detect_deadlock __IP_DECL__)
+{
+ int res = 0;
+ struct rt_mutex_waiter *top_waiter = waiter;
+ LIST_HEAD(lock_chain);
+
+ waiter->task = current;
+ waiter->lock = lock;
+ debug_rt_mutex_reset_waiter(waiter);
+
+ spin_lock(¤t->pi_lock);
+ current->pi_locked_by = current;
+ plist_node_init(&waiter->list_entry, current->prio);
+ plist_node_init(&waiter->pi_list_entry, current->prio);
+
+ /* Get the top priority waiter of the lock: */
+ if (rt_mutex_has_waiters(lock))
+ top_waiter = rt_mutex_top_waiter(lock);
+ plist_add(&waiter->list_entry, &lock->wait_list);
+
+ current->pi_blocked_on = waiter;
+
+ /*
+ * Call adjust_prio_chain, when waiter is the new top waiter
+ * or when deadlock detection is requested:
+ */
+ if (waiter != rt_mutex_top_waiter(lock) &&
+ !debug_rt_mutex_detect_deadlock(detect_deadlock))
+ goto out;
+
+ /* Try to lock the full chain: */
+ res = lock_pi_chain(lock, waiter, &lock_chain, 1, detect_deadlock);
+
+ if (likely(!res))
+ adjust_pi_chain(lock, waiter, top_waiter, &lock_chain);
+
+ /* Common case: we managed to lock it: */
+ if (res != -EBUSY)
+ goto out_unlock;
+
+ /* Rare case: we hit some other task running a pi chain operation: */
+ unlock_pi_chain(&lock_chain);
+
+ plist_del(&waiter->list_entry, &lock->wait_list);
+ current->pi_blocked_on = NULL;
+ current->pi_locked_by = NULL;
+ spin_unlock(¤t->pi_lock);
+ fixup_rt_mutex_waiters(lock);
+
+ spin_unlock(&lock->wait_lock);
+
+ spin_lock(&pi_conflicts_lock);
+
+ spin_lock(¤t->pi_lock);
+ current->pi_locked_by = current;
+ spin_lock(&lock->wait_lock);
+ if (!rt_mutex_owner(lock)) {
+ waiter->task = NULL;
+ spin_unlock(&pi_conflicts_lock);
+ goto out;
+ }
+ plist_node_init(&waiter->list_entry, current->prio);
+ plist_node_init(&waiter->pi_list_entry, current->prio);
+
+ /* Get the top priority waiter of the lock: */
+ if (rt_mutex_has_waiters(lock))
+ top_waiter = rt_mutex_top_waiter(lock);
+ plist_add(&waiter->list_entry, &lock->wait_list);
+
+ current->pi_blocked_on = waiter;
+
+ /* Lock the full chain: */
+ res = lock_pi_chain(lock, waiter, &lock_chain, 0, detect_deadlock);
+
+ /* Drop the conflicts lock before adjusting: */
+ spin_unlock(&pi_conflicts_lock);
+
+ if (likely(!res))
+ adjust_pi_chain(lock, waiter, top_waiter, &lock_chain);
+
+ out_unlock:
+ unlock_pi_chain(&lock_chain);
+ out:
+ current->pi_locked_by = NULL;
+ spin_unlock(¤t->pi_lock);
+ return res;
+}
+
+/*
+ * Optimization: check if we can steal the lock from the
+ * assigned pending owner [which might not have taken the
+ * lock yet]:
+ */
+static inline int try_to_steal_lock(struct rt_mutex *lock)
+{
+ struct task_struct *pendowner = rt_mutex_owner(lock);
+ struct rt_mutex_waiter *next;
+
+ if (!rt_mutex_owner_pending(lock))
+ return 0;
+
+ if (pendowner == current)
+ return 1;
+
+ spin_lock(&pendowner->pi_lock);
+ if (current->prio >= pendowner->prio) {
+ spin_unlock(&pendowner->pi_lock);
+ return 0;
+ }
+
+ /*
+ * Check if a waiter is enqueued on the pending owners
+ * pi_waiters list. Remove it and readjust pending owners
+ * priority.
+ */
+ if (likely(!rt_mutex_has_waiters(lock))) {
+ spin_unlock(&pendowner->pi_lock);
+ return 1;
+ }
+
+ /* No chain handling, pending owner is not blocked on anything: */
+ next = rt_mutex_top_waiter(lock);
+ plist_del(&next->pi_list_entry, &pendowner->pi_waiters);
+ __rt_mutex_adjust_prio(pendowner);
+ spin_unlock(&pendowner->pi_lock);
+
+ /*
+ * We are going to steal the lock and a waiter was
+ * enqueued on the pending owners pi_waiters queue. So
+ * we have to enqueue this waiter into
+ * current->pi_waiters list. This covers the case,
+ * where current is boosted because it holds another
+ * lock and gets unboosted because the booster is
+ * interrupted, so we would delay a waiter with higher
+ * priority as current->normal_prio.
+ *
+ * Note: in the rare case of a SCHED_OTHER task changing
+ * its priority and thus stealing the lock, next->task
+ * might be current:
+ */
+ if (likely(next->task != current)) {
+ spin_lock(¤t->pi_lock);
+ plist_add(&next->pi_list_entry, ¤t->pi_waiters);
+ __rt_mutex_adjust_prio(current);
+ spin_unlock(¤t->pi_lock);
+ }
+ return 1;
+}
+
+/*
+ * Try to take an rt-mutex
+ *
+ * This fails
+ * - when the lock has a real owner
+ * - when a different pending owner exists and has higher priority than current
+ *
+ * Must be called with lock->wait_lock held.
+ */
+static int try_to_take_rt_mutex(struct rt_mutex *lock __IP_DECL__)
+{
+ /*
+ * 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.
+ */
+ mark_rt_mutex_waiters(lock);
+
+ if (rt_mutex_owner(lock) && !try_to_steal_lock(lock))
+ return 0;
+
+ /* We got the lock. */
+ debug_rt_mutex_lock(lock __IP__);
+
+ rt_mutex_set_owner(lock, current, 0);
+
+ rt_mutex_deadlock_account_lock(lock, current);
+
+ return 1;
+}
+
+/*
+ * Wake up the next waiter on the lock.
+ *
+ * Remove the top waiter from the current tasks waiter list and from
+ * the lock waiter list. Set it as pending owner. Then wake it up.
+ *
+ * Called with lock->wait_lock held.
+ */
+static void wakeup_next_waiter(struct rt_mutex *lock)
+{
+ struct rt_mutex_waiter *waiter;
+ struct task_struct *pendowner;
+
+ waiter = rt_mutex_top_waiter(lock);
+ plist_del(&waiter->list_entry, &lock->wait_list);
+
+ /*
+ * 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.
+ */
+ spin_lock(¤t->pi_lock);
+ plist_del(&waiter->pi_list_entry, ¤t->pi_waiters);
+ spin_unlock(¤t->pi_lock);
+
+ pendowner = waiter->task;
+ waiter->task = NULL;
+
+ rt_mutex_set_owner(lock, pendowner, RT_MUTEX_OWNER_PENDING);
+
+ /*
+ * 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(&pendowner->pi_lock);
+
+ 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(&pendowner->pi_lock);
+
+ wake_up_process(pendowner);
+}
+
+/*
+ * Remove a waiter from a lock
+ *
+ * Must be called with lock->wait_lock held.
+ */
+static int remove_waiter(struct rt_mutex *lock,
+ struct rt_mutex_waiter *waiter __IP_DECL__)
+{
+ struct rt_mutex_waiter *next_waiter = NULL,
+ *top_waiter = rt_mutex_top_waiter(lock);
+ LIST_HEAD(lock_chain);
+ int res;
+
+ plist_del(&waiter->list_entry, &lock->wait_list);
+
+ spin_lock(¤t->pi_lock);
+
+ if (waiter != top_waiter || rt_mutex_owner(lock) == current)
+ goto out;
+
+ current->pi_locked_by = current;
+
+ if (rt_mutex_has_waiters(lock))
+ next_waiter = rt_mutex_top_waiter(lock);
+
+ /* Try to lock the full chain: */
+ res = lock_pi_chain(lock, next_waiter, &lock_chain, 1, 0);
+
+ if (likely(res != -EBUSY)) {
+ adjust_pi_chain(lock, next_waiter, waiter, &lock_chain);
+ goto out_unlock;
+ }
+
+ /* We hit some other task running a pi chain operation: */
+ unlock_pi_chain(&lock_chain);
+ plist_add(&waiter->list_entry, &lock->wait_list);
+ current->pi_blocked_on = waiter;
+ current->pi_locked_by = NULL;
+ spin_unlock(¤t->pi_lock);
+ spin_unlock(&lock->wait_lock);
+
+ spin_lock(&pi_conflicts_lock);
+
+ spin_lock(¤t->pi_lock);
+ current->pi_locked_by = current;
+
+ spin_lock(&lock->wait_lock);
+
+ /* We might have been woken up: */
+ if (!waiter->task) {
+ spin_unlock(&pi_conflicts_lock);
+ goto out;
+ }
+
+ top_waiter = rt_mutex_top_waiter(lock);
+
+ plist_del(&waiter->list_entry, &lock->wait_list);
+
+ if (waiter != top_waiter || rt_mutex_owner(lock) == current)
+ goto out;
+
+ /* Get the top priority waiter of the lock: */
+ if (rt_mutex_has_waiters(lock))
+ next_waiter = rt_mutex_top_waiter(lock);
+
+ /* Lock the full chain: */
+ lock_pi_chain(lock, next_waiter, &lock_chain, 0, 0);
+
+ /* Drop the conflicts lock: */
+ spin_unlock(&pi_conflicts_lock);
+
+ adjust_pi_chain(lock, next_waiter, waiter, &lock_chain);
+
+ out_unlock:
+ unlock_pi_chain(&lock_chain);
+ out:
+ current->pi_blocked_on = NULL;
+ waiter->task = NULL;
+ current->pi_locked_by = NULL;
+ spin_unlock(¤t->pi_lock);
+
+ WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
+
+ return 0;
+}
+
+/*
+ * Slow path lock function:
+ */
+static int fastcall noinline __sched
+rt_mutex_slowlock(struct rt_mutex *lock, int state,
+ struct hrtimer_sleeper *timeout,
+ int detect_deadlock __IP_DECL__)
+{
+ struct rt_mutex_waiter waiter;
+ int ret = 0;
+ unsigned long flags;
+
+ debug_rt_mutex_init_waiter(&waiter);
+ waiter.task = NULL;
+
+ spin_lock_irqsave(&lock->wait_lock, flags);
+
+ /* Try to acquire the lock again: */
+ if (try_to_take_rt_mutex(lock __IP__)) {
+ spin_unlock_irqrestore(&lock->wait_lock, flags);
+ return 0;
+ }
+
+ BUG_ON(rt_mutex_owner(lock) == current);
+
+ set_task_state(current, state);
+
+ /* Setup the timer, when timeout != NULL */
+ if (unlikely(timeout))
+ hrtimer_start(&timeout->timer, timeout->timer.expires,
+ HRTIMER_ABS);
+
+ for (;;) {
+ /* Try to acquire the lock: */
+ if (try_to_take_rt_mutex(lock __IP__))
+ 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 an higher prio task.
+ */
+ if (!waiter.task) {
+ ret = task_blocks_on_rt_mutex(lock, &waiter,
+ detect_deadlock __IP__);
+ if (ret == -EDEADLK)
+ break;
+ if (ret == -EBUSY)
+ continue;
+ }
+
+ spin_unlock_irqrestore(&lock->wait_lock, flags);
+
+ debug_rt_mutex_print_deadlock(&waiter);
+
+ schedule();
+
+ spin_lock_irqsave(&lock->wait_lock, flags);
+ set_task_state(current, state);
+ }
+
+ set_task_state(current, TASK_RUNNING);
+
+ if (unlikely(waiter.task))
+ remove_waiter(lock, &waiter __IP__);
+
+ /*
+ * try_to_take_rt_mutex() sets the waiter bit
+ * unconditionally. We might have to fix that up.
+ */
+ fixup_rt_mutex_waiters(lock);
+
+ spin_unlock_irqrestore(&lock->wait_lock, flags);
+
+ /* Remove pending timer: */
+ if (unlikely(timeout && timeout->task))
+ 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 fastcall
+rt_mutex_slowtrylock(struct rt_mutex *lock __IP_DECL__)
+{
+ unsigned long flags;
+ int ret = 0;
+
+ spin_lock_irqsave(&lock->wait_lock, flags);
+
+ if (likely(rt_mutex_owner(lock) != current)) {
+
+ ret = try_to_take_rt_mutex(lock __IP__);
+ /*
+ * try_to_take_rt_mutex() sets the lock waiters
+ * bit. We might be the only waiter. Check if this
+ * needs to be cleaned up.
+ */
+ if (!ret)
+ fixup_rt_mutex_waiters(lock);
+ }
+
+ spin_unlock_irqrestore(&lock->wait_lock, flags);
+
+ return ret;
+}
+
+/*
+ * Slow path to release a rt-mutex:
+ */
+static void fastcall noinline __sched
+rt_mutex_slowunlock(struct rt_mutex *lock)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&lock->wait_lock, flags);
+
+ debug_rt_mutex_unlock(lock);
+
+ rt_mutex_deadlock_account_unlock(current);
+
+ if (!rt_mutex_has_waiters(lock)) {
+ lock->owner = NULL;
+ spin_unlock_irqrestore(&lock->wait_lock, flags);
+ return;
+ }
+
+ wakeup_next_waiter(lock);
+
+ spin_unlock_irqrestore(&lock->wait_lock, flags);
+
+ /* 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 fastcall (*slowfn)(struct rt_mutex *lock, int state,
+ struct hrtimer_sleeper *timeout,
+ int detect_deadlock __IP_DECL__))
+{
+ 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 __RET_IP__);
+}
+
+static inline int
+rt_mutex_timed_fastlock(struct rt_mutex *lock, int state,
+ struct hrtimer_sleeper *timeout, int detect_deadlock,
+ int fastcall (*slowfn)(struct rt_mutex *lock, int state,
+ struct hrtimer_sleeper *timeout,
+ int detect_deadlock __IP_DECL__))
+{
+ 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 __RET_IP__);
+}
+
+static inline int
+rt_mutex_fasttrylock(struct rt_mutex *lock,
+ int fastcall (*slowfn)(struct rt_mutex *lock __IP_DECL__))
+{
+ if (likely(rt_mutex_cmpxchg(lock, NULL, current))) {
+ rt_mutex_deadlock_account_lock(lock, current);
+ return 1;
+ }
+ return slowfn(lock __RET_IP__);
+}
+
+static inline void
+rt_mutex_fastunlock(struct rt_mutex *lock,
+ void fastcall (*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 fastcall __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 fastcall __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 fastcall
+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 fastcall __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 fastcall __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 fastcall 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 fastcall __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);
+
+ debug_rt_mutex_init(lock, name);
+}
+EXPORT_SYMBOL_GPL(__rt_mutex_init);
Index: linux-pi-futex.mm.q/kernel/rtmutex.h
===================================================================
--- /dev/null
+++ linux-pi-futex.mm.q/kernel/rtmutex.h
@@ -0,0 +1,28 @@
+/*
+ * RT-Mutexes: blocking mutual exclusion locks with PI support
+ *
+ * started by Ingo Molnar and Thomas Gleixner:
+ *
+ * Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <[email protected]>
+ * Copyright (C) 2006, Timesys Corp., Thomas Gleixner <[email protected]>
+ *
+ * This file contains macros used solely by rtmutex.c.
+ * Non-debug version.
+ */
+
+#define __IP_DECL__
+#define __IP__
+#define __RET_IP__
+#define rt_mutex_deadlock_check(l) (0)
+#define rt_mutex_deadlock_account_lock(m, t) do { } while (0)
+#define rt_mutex_deadlock_account_unlock(l) do { } while (0)
+#define debug_rt_mutex_init_waiter(w) do { } while (0)
+#define debug_rt_mutex_free_waiter(w) do { } while (0)
+#define debug_rt_mutex_lock(l) do { } while (0)
+#define debug_rt_mutex_proxy_unlock(l) do { } while (0)
+#define debug_rt_mutex_unlock(l) do { } while (0)
+#define debug_rt_mutex_init(m, n) do { } while (0)
+#define debug_rt_mutex_deadlock(d, a ,l) do { } while (0)
+#define debug_rt_mutex_print_deadlock(w) do { } while (0)
+#define debug_rt_mutex_detect_deadlock(d) (d)
+#define debug_rt_mutex_reset_waiter(w) do { } while (0)
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