projects/linux·commit 23f78d4a

[PATCH] pi-futex: rt mutex core

23f78d4a · Ingo Molnar <[email protected]> · 2006-06-27 02:54:53 -07:00

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]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Commit
23f78d4a03c53cbd75d87a795378ea540aa08c86
Parents
b29739f9

Changes

11 files changed · +1181 −0

FileStatusAddDelContent
include/linux/init_task.hmodified+1−0View file
include/linux/rtmutex.hadded+104−0View file
include/linux/sched.hmodified+12−0View file
include/linux/sysctl.hmodified+1−0View file
init/Kconfigmodified+5−0View file
kernel/Makefilemodified+1−0View file
kernel/fork.cmodified+16−0View file
kernel/rtmutex.cadded+904−0View file
kernel/rtmutex.hadded+29−0View file
kernel/rtmutex_common.hadded+93−0View file
kernel/sysctl.cmodified+15−0View file

Only the first 600 diff lines are shown. Download the complete patch.

include/linux/init_task.h

View file
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 678c1a9..3a25695 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -124,6 +124,7 @@ extern struct group_info init_groups;
.cpu_timers = INIT_CPU_TIMERS(tsk.cpu_timers), \
.fs_excl = ATOMIC_INIT(0), \
.pi_lock = SPIN_LOCK_UNLOCKED, \
+ INIT_RT_MUTEXES(tsk) \
}

include/linux/rtmutex.h

View file
diff --git a/include/linux/rtmutex.h b/include/linux/rtmutex.h
new file mode 100644
index 0000000..12309c9
--- /dev/null
+++ b/include/linux/rtmutex.h
@@ -0,0 +1,104 @@
+/*
+ * 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_entry;
+ 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, mutexname.wait_lock) \
+ , .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 rt_mutex_is_locked(struct rt_mutex *lock)
+{
+ return lock->owner != NULL;
+}
+
+extern void __rt_mutex_init(struct rt_mutex *lock, const char *name);
+extern void rt_mutex_destroy(struct rt_mutex *lock);
+
+extern void rt_mutex_lock(struct rt_mutex *lock);
+extern int rt_mutex_lock_interruptible(struct rt_mutex *lock,
+ int detect_deadlock);
+extern int rt_mutex_timed_lock(struct rt_mutex *lock,
+ struct hrtimer_sleeper *timeout,
+ int detect_deadlock);
+
+extern int rt_mutex_trylock(struct rt_mutex *lock);
+
+extern void rt_mutex_unlock(struct rt_mutex *lock);
+
+#ifdef CONFIG_DEBUG_RT_MUTEXES
+# define INIT_RT_MUTEX_DEBUG(tsk) \
+ .held_list_head = LIST_HEAD_INIT(tsk.held_list_head), \
+ .held_list_lock = SPIN_LOCK_UNLOCKED
+#else
+# define INIT_RT_MUTEX_DEBUG(tsk)
+#endif
+
+#ifdef CONFIG_RT_MUTEXES
+# define INIT_RT_MUTEXES(tsk) \
+ .pi_waiters = PLIST_HEAD_INIT(tsk.pi_waiters, tsk.pi_lock), \
+ INIT_RT_MUTEX_DEBUG(tsk)
+#else
+# define INIT_RT_MUTEXES(tsk)
+#endif
+
+#endif

include/linux/sched.h

View file
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6f16764..6ea23c9 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -73,6 +73,7 @@ struct sched_param {
#include <linux/seccomp.h>
#include <linux/rcupdate.h>
#include <linux/futex.h>
+#include <linux/rtmutex.h>
#include <linux/time.h>
#include <linux/param.h>
@@ -858,6 +859,17 @@ 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;
+# ifdef CONFIG_DEBUG_RT_MUTEXES
+ spinlock_t held_list_lock;
+ struct list_head held_list_head;
+# endif
+#endif
+
#ifdef CONFIG_DEBUG_MUTEXES
/* mutex deadlock detection */
struct mutex_waiter *blocked_on;

include/linux/sysctl.h

View file
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index bee12a7..46e4d8f 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -149,6 +149,7 @@ enum
KERN_ACPI_VIDEO_FLAGS=71, /* int: flags for setting up video after ACPI sleep */
KERN_IA64_UNALIGNED=72, /* int: ia64 unaligned userland trap enable */
KERN_COMPAT_LOG=73, /* int: print compat layer messages */
+ KERN_MAX_LOCK_DEPTH=74,
};

init/Kconfig

View file
diff --git a/init/Kconfig b/init/Kconfig
index df55b36..f70f2fd 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -339,9 +339,14 @@ 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

kernel/Makefile

View file
diff --git a/kernel/Makefile b/kernel/Makefile
index 752bd7d..21df9a3 100644
--- a/kernel/Makefile
+++ b/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

kernel/fork.c

View file
diff --git a/kernel/fork.c b/kernel/fork.c
index 9b4e54e..b664a08 100644
--- a/kernel/fork.c
+++ b/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);
@@ -913,6 +914,19 @@ asmlinkage long sys_set_tid_address(int __user *tidptr)
return current->pid;
}
+static inline void rt_mutex_init_task(struct task_struct *p)
+{
+#ifdef CONFIG_RT_MUTEXES
+ spin_lock_init(&p->pi_lock);
+ plist_head_init(&p->pi_waiters, &p->pi_lock);
+ p->pi_blocked_on = NULL;
+# ifdef CONFIG_DEBUG_RT_MUTEXES
+ spin_lock_init(&p->held_list_lock);
+ INIT_LIST_HEAD(&p->held_list_head);
+# endif
+#endif
+}
+
/*
* This creates a new process as a copy of the old one,
* but does not actually start it yet.
@@ -1034,6 +1048,8 @@ static task_t *copy_process(unsigned long clone_flags,
mpol_fix_fork_child_flag(p);
#endif
+ rt_mutex_init_task(p);
+
#ifdef CONFIG_DEBUG_MUTEXES
p->blocked_on = NULL; /* not blocked yet */
#endif

kernel/rtmutex.c

View file
diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
new file mode 100644
index 0000000..937a474
--- /dev/null
+++ b/kernel/rtmutex.c
@@ -0,0 +1,904 @@
+/*
+ * 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) 2005-2006 Timesys Corp., Thomas Gleixner <[email protected]>
+ * Copyright (C) 2005 Kihon Technologies Inc., Steven Rostedt
+ * Copyright (C) 2006 Esben Nielsen
+ */
+#include <linux/spinlock.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/timer.h>
+
+#include "rtmutex_common.h"
+
+#ifdef CONFIG_DEBUG_RT_MUTEXES
+# include "rtmutex-debug.h"
+#else
+# include "rtmutex.h"
+#endif
+
+/*
+ * 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 Transitional 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.
+ *
+ * (*) There's a small time where the owner can be NULL and the
+ * "lock has waiters" bit is set. This can happen when grabbing the lock.
+ * To prevent a cmpxchg of the owner releasing the lock, we need to set this
+ * bit before looking at the lock, hence the reason this is a transitional
+ * state.
+ */
+
+static void
+rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner,
+ unsigned long mask)
+{
+ unsigned long val = (unsigned long)owner | mask;
+
+ if (rt_mutex_has_waiters(lock))
+ val |= RT_MUTEX_HAS_WAITERS;
+
+ lock->owner = (struct task_struct *)val;
+}
+
+static inline void clear_rt_mutex_waiters(struct rt_mutex *lock)
+{
+ lock->owner = (struct task_struct *)
+ ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS);
+}
+
+static void fixup_rt_mutex_waiters(struct rt_mutex *lock)
+{
+ if (!rt_mutex_has_waiters(lock))
+ clear_rt_mutex_waiters(lock);
+}
+
+/*
+ * We can speed up the acquire/release, if the architecture
+ * supports cmpxchg and if there's no debugging state to be set up
+ */
+#if defined(__HAVE_ARCH_CMPXCHG) && !defined(CONFIG_DEBUG_RT_MUTEXES)
+# define rt_mutex_cmpxchg(l,c,n) (cmpxchg(&l->owner, c, n) == c)
+static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
+{
+ unsigned long owner, *p = (unsigned long *) &lock->owner;
+
+ do {
+ owner = *p;
+ } while (cmpxchg(p, owner, owner | RT_MUTEX_HAS_WAITERS) != owner);
+}
+#else
+# define rt_mutex_cmpxchg(l,c,n) (0)
+static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
+{
+ lock->owner = (struct task_struct *)
+ ((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS);
+}
+#endif
+
+/*
+ * Calculate task priority from the waiter list priority
+ *
+ * Return task->normal_prio when the waiter list is empty or when
+ * the waiter is not allowed to do priority boosting
+ */
+int rt_mutex_getprio(struct task_struct *task)
+{
+ if (likely(!task_has_pi_waiters(task)))
+ return task->normal_prio;
+
+ return min(task_top_pi_waiter(task)->pi_list_entry.prio,
+ task->normal_prio);
+}
+
+/*
+ * Adjust the priority of a task, after its pi_waiters got modified.
+ *
+ * This can be both boosting and unboosting. task->pi_lock must be held.
+ */
+static void __rt_mutex_adjust_prio(struct task_struct *task)
+{
+ int prio = rt_mutex_getprio(task);
+
+ if (task->prio != prio)
+ rt_mutex_setprio(task, prio);
+}
+
+/*
+ * Adjust task priority (undo boosting). Called from the exit path of
+ * rt_mutex_slowunlock() and rt_mutex_slowlock().
+ *
+ * (Note: We do this outside of the protection of lock->wait_lock to
+ * allow the lock to be taken while or before we readjust the priority
+ * of task. We do not use the spin_xx_mutex() variants here as we are
+ * outside of the debug path.)
+ */
+static void rt_mutex_adjust_prio(struct task_struct *task)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&task->pi_lock, flags);
+ __rt_mutex_adjust_prio(task);
+ spin_unlock_irqrestore(&task->pi_lock, flags);
+}
+
+/*
+ * Max number of times we'll walk the boosting chain:
+ */
+int max_lock_depth = 1024;
+
+/*
+ * Adjust the priority chain. Also used for deadlock detection.
+ * Decreases task's usage by one - may thus free the task.
+ * Returns 0 or -EDEADLK.
+ */
+static int rt_mutex_adjust_prio_chain(task_t *task,
+ int deadlock_detect,
+ struct rt_mutex *orig_lock,
+ struct rt_mutex_waiter *orig_waiter
+ __IP_DECL__)
+{
+ struct rt_mutex *lock;
+ struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter;
+ int detect_deadlock, ret = 0, depth = 0;
+ unsigned long flags;
+
+ detect_deadlock = debug_rt_mutex_detect_deadlock(orig_waiter,
+ deadlock_detect);
+
+ /*
+ * The (de)boosting is a step by step approach with a lot of
+ * pitfalls. We want this to be preemptible and we want hold a
+ * maximum of two locks per step. So we have to check
+ * carefully whether things change under us.
+ */
+ again:
+ if (++depth > max_lock_depth) {
+ static int prev_max;
+
+ /*
+ * Print this only once. If the admin changes the limit,
+ * print a new message when reaching the limit again.
+ */
+ if (prev_max != max_lock_depth) {
+ prev_max = max_lock_depth;
+ printk(KERN_WARNING "Maximum lock depth %d reached "
+ "task: %s (%d)\n", max_lock_depth,
+ current->comm, current->pid);
+ }
+ put_task_struct(task);
+
+ return deadlock_detect ? -EDEADLK : 0;
+ }
+ retry:
+ /*
+ * Task can not go away as we did a get_task() before !
+ */
+ spin_lock_irqsave(&task->pi_lock, flags);
+
+ waiter = task->pi_blocked_on;
+ /*
+ * Check whether the end of the boosting chain has been
+ * reached or the state of the chain has changed while we
+ * dropped the locks.
+ */
+ if (!waiter || !waiter->task)
+ goto out_unlock_pi;
+
+ if (top_waiter && (!task_has_pi_waiters(task) ||
+ top_waiter != task_top_pi_waiter(task)))
+ goto out_unlock_pi;
+
+ /*
+ * When deadlock detection is off then we check, if further
+ * priority adjustment is necessary.
+ */
+ if (!detect_deadlock && waiter->list_entry.prio == task->prio)
+ goto out_unlock_pi;
+
+ lock = waiter->lock;
+ if (!spin_trylock(&lock->wait_lock)) {
+ spin_unlock_irqrestore(&task->pi_lock, flags);
+ cpu_relax();
+ goto retry;
+ }
+
+ /* Deadlock detection */
+ if (lock == orig_lock || rt_mutex_owner(lock) == current) {
+ debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock);
+ spin_unlock(&lock->wait_lock);
+ ret = deadlock_detect ? -EDEADLK : 0;
+ goto out_unlock_pi;
+ }
+
+ top_waiter = rt_mutex_top_waiter(lock);
+
+ /* Requeue the waiter */
+ plist_del(&waiter->list_entry, &lock->wait_list);
+ waiter->list_entry.prio = task->prio;
+ plist_add(&waiter->list_entry, &lock->wait_list);
+
+ /* Release the task */
+ spin_unlock_irqrestore(&task->pi_lock, flags);
+ put_task_struct(task);
+
+ /* Grab the next task */
+ task = rt_mutex_owner(lock);
+ spin_lock_irqsave(&task->pi_lock, flags);
+
+ if (waiter == rt_mutex_top_waiter(lock)) {
+ /* Boost the owner */
+ plist_del(&top_waiter->pi_list_entry, &task->pi_waiters);
+ waiter->pi_list_entry.prio = waiter->list_entry.prio;
+ plist_add(&waiter->pi_list_entry, &task->pi_waiters);
+ __rt_mutex_adjust_prio(task);
+
+ } else if (top_waiter == waiter) {
+ /* Deboost the owner */
+ plist_del(&waiter->pi_list_entry, &task->pi_waiters);
+ waiter = rt_mutex_top_waiter(lock);
+ waiter->pi_list_entry.prio = waiter->list_entry.prio;
+ plist_add(&waiter->pi_list_entry, &task->pi_waiters);
+ __rt_mutex_adjust_prio(task);
+ }
+
+ get_task_struct(task);
+ spin_unlock_irqrestore(&task->pi_lock, flags);
+
+ top_waiter = rt_mutex_top_waiter(lock);
+ spin_unlock(&lock->wait_lock);
+
+ if (!detect_deadlock && waiter != top_waiter)
+ goto out_put_task;
+
+ goto again;
+
+ out_unlock_pi:
+ spin_unlock_irqrestore(&task->pi_lock, flags);
+ out_put_task:
+ put_task_struct(task);
+ return ret;
+}
+
+/*
+ * 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;
+ unsigned long flags;
+
+ if (!rt_mutex_owner_pending(lock))
+ return 0;
+
+ if (pendowner == current)
+ return 1;
+
+ spin_lock_irqsave(&pendowner->pi_lock, flags);
+ if (current->prio >= pendowner->prio) {
+ spin_unlock_irqrestore(&pendowner->pi_lock, flags);
+ 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_irqrestore(&pendowner->pi_lock, flags);
+ 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_irqrestore(&pendowner->pi_lock, flags);
+
+ /*
+ * 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_irqsave(&current->pi_lock, flags);
+ plist_add(&next->pi_list_entry, &current->pi_waiters);
+ __rt_mutex_adjust_prio(current);
+ spin_unlock_irqrestore(&current->pi_lock, flags);
+ }
+ 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.
+ */

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kernel/rtmutex.h

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kernel/rtmutex_common.h

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kernel/sysctl.c

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