From: Ingo Molnar <[email protected]>
this adds the actual pi-futex implementation, based on rt-mutexes.
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/futex.h | 6
include/linux/sched.h | 3
kernel/exit.c | 8
kernel/fork.c | 3
kernel/futex.c | 696 +++++++++++++++++++++++++++++++++++++++++++++++---
kernel/futex_compat.c | 11
6 files changed, 686 insertions(+), 41 deletions(-)
Index: linux-pi-futex.mm.q/include/linux/futex.h
===================================================================
--- linux-pi-futex.mm.q.orig/include/linux/futex.h
+++ linux-pi-futex.mm.q/include/linux/futex.h
@@ -12,6 +12,8 @@
#define FUTEX_REQUEUE 3
#define FUTEX_CMP_REQUEUE 4
#define FUTEX_WAKE_OP 5
+#define FUTEX_LOCK_PI 6
+#define FUTEX_UNLOCK_PI 7
/*
* Support for robust futexes: the kernel cleans up held futexes at
@@ -97,10 +99,14 @@ extern int handle_futex_death(u32 __user
#ifdef CONFIG_FUTEX
extern void exit_robust_list(struct task_struct *curr);
+extern void exit_pi_state_list(struct task_struct *curr);
#else
static inline void exit_robust_list(struct task_struct *curr)
{
}
+static inline void exit_pi_state_list(struct task_struct *curr)
+{
+}
#endif
#define FUTEX_OP_SET 0 /* *(int *)UADDR2 = OPARG; */
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
@@ -705,6 +705,7 @@ static inline void prefetch_stack(struct
struct audit_context; /* See audit.c */
struct mempolicy;
+struct futex_pi_state;
enum sleep_type {
SLEEP_NORMAL,
@@ -917,6 +918,8 @@ struct task_struct {
#ifdef CONFIG_COMPAT
struct compat_robust_list_head __user *compat_robust_list;
#endif
+ struct list_head pi_state_list;
+ struct futex_pi_state *pi_state_cache;
atomic_t fs_excl; /* holding fs exclusive resources */
struct rcu_head rcu;
Index: linux-pi-futex.mm.q/kernel/exit.c
===================================================================
--- linux-pi-futex.mm.q.orig/kernel/exit.c
+++ linux-pi-futex.mm.q/kernel/exit.c
@@ -928,6 +928,14 @@ fastcall NORET_TYPE void do_exit(long co
tsk->mempolicy = NULL;
#endif
/*
+ * This must happen late, after the PID is not
+ * hashed anymore:
+ */
+ if (unlikely(!list_empty(&tsk->pi_state_list)))
+ exit_pi_state_list(tsk);
+ if (unlikely(current->pi_state_cache))
+ kfree(current->pi_state_cache);
+ /*
* If DEBUG_MUTEXES is on, make sure we are holding no locks:
*/
mutex_debug_check_no_locks_held(tsk);
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
@@ -1087,6 +1087,9 @@ static task_t *copy_process(unsigned lon
#ifdef CONFIG_COMPAT
p->compat_robust_list = NULL;
#endif
+ INIT_LIST_HEAD(&p->pi_state_list);
+ p->pi_state_cache = NULL;
+
/*
* sigaltstack should be cleared when sharing the same VM
*/
Index: linux-pi-futex.mm.q/kernel/futex.c
===================================================================
--- linux-pi-futex.mm.q.orig/kernel/futex.c
+++ linux-pi-futex.mm.q/kernel/futex.c
@@ -12,6 +12,10 @@
* (C) Copyright 2006 Red Hat Inc, All Rights Reserved
* Thanks to Thomas Gleixner for suggestions, analysis and fixes.
*
+ * PI-futex support started by Ingo Molnar and Thomas Gleixner
+ * Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <[email protected]>
+ * Copyright (C) 2006 Timesys Corp., Thomas Gleixner <[email protected]>
+ *
* Thanks to Ben LaHaise for yelling "hashed waitqueues" loudly
* enough at me, Linus for the original (flawed) idea, Matthew
* Kirkwood for proof-of-concept implementation.
@@ -44,6 +48,7 @@
#include <linux/pagemap.h>
#include <linux/syscalls.h>
#include <linux/signal.h>
+#include <linux/rtmutex_internal.h>
#include <asm/futex.h>
#define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
@@ -75,6 +80,27 @@ union futex_key {
};
/*
+ * Priority Inheritance state:
+ */
+struct futex_pi_state {
+ /*
+ * list of 'owned' pi_state instances - these have to be
+ * cleaned up in do_exit() if the task exits prematurely:
+ */
+ struct list_head list;
+
+ /*
+ * The PI object:
+ */
+ struct rt_mutex pi_mutex;
+
+ struct task_struct *owner;
+ atomic_t refcount;
+
+ union futex_key key;
+};
+
+/*
* We use this hashed waitqueue instead of a normal wait_queue_t, so
* we can wake only the relevant ones (hashed queues may be shared).
*
@@ -96,6 +122,10 @@ struct futex_q {
/* For fd, sigio sent using these: */
int fd;
struct file *filp;
+
+ /* Optional priority inheritance state: */
+ struct futex_pi_state *pi_state;
+ struct task_struct *task;
};
/*
@@ -260,6 +290,228 @@ static inline int get_futex_value_locked
}
/*
+ * Fault handling. Called with current->mm->mmap_sem held.
+ */
+static int futex_handle_fault(unsigned long address, int attempt)
+{
+ struct vm_area_struct * vma;
+ struct mm_struct *mm = current->mm;
+
+ if (attempt >= 2 || !(vma = find_vma(mm, address)) ||
+ vma->vm_start > address || !(vma->vm_flags & VM_WRITE))
+ return -EFAULT;
+
+ switch (handle_mm_fault(mm, vma, address, 1)) {
+ case VM_FAULT_MINOR:
+ current->min_flt++;
+ break;
+ case VM_FAULT_MAJOR:
+ current->maj_flt++;
+ break;
+ default:
+ return -EFAULT;
+ }
+ return 0;
+}
+
+/*
+ * PI code:
+ */
+static int refill_pi_state_cache(void)
+{
+ struct futex_pi_state *pi_state;
+
+ if (likely(current->pi_state_cache))
+ return 0;
+
+ pi_state = kmalloc(sizeof(*pi_state), GFP_KERNEL);
+
+ if (!pi_state)
+ return -ENOMEM;
+
+ memset(pi_state, 0, sizeof(*pi_state));
+ INIT_LIST_HEAD(&pi_state->list);
+ /* pi_mutex gets initialized later */
+ pi_state->owner = NULL;
+ atomic_set(&pi_state->refcount, 1);
+
+ current->pi_state_cache = pi_state;
+
+ return 0;
+}
+
+static struct futex_pi_state * alloc_pi_state(void)
+{
+ struct futex_pi_state *pi_state = current->pi_state_cache;
+
+ WARN_ON(!pi_state);
+ current->pi_state_cache = NULL;
+
+ return pi_state;
+}
+
+static void free_pi_state(struct futex_pi_state *pi_state)
+{
+ if (!atomic_dec_and_test(&pi_state->refcount))
+ return;
+
+ WARN_ON(!pi_state->owner);
+ WARN_ON(!rt_mutex_is_locked(&pi_state->pi_mutex));
+
+ spin_lock(&pi_state->owner->pi_lock);
+ list_del_init(&pi_state->list);
+ spin_unlock(&pi_state->owner->pi_lock);
+
+ rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner);
+
+ if (current->pi_state_cache)
+ kfree(pi_state);
+ else {
+ /*
+ * pi_state->list is already empty.
+ * clear pi_state->owner.
+ * refcount is at 0 - put it back to 1.
+ */
+ pi_state->owner = NULL;
+ atomic_set(&pi_state->refcount, 1);
+ current->pi_state_cache = pi_state;
+ }
+}
+
+/*
+ * Look up the task based on what TID userspace gave us.
+ * We dont trust it.
+ */
+static struct task_struct * futex_find_get_task(pid_t pid)
+{
+ struct task_struct *p;
+
+ read_lock(&tasklist_lock);
+ p = find_task_by_pid(pid);
+ if (!p)
+ goto out_unlock;
+ if ((current->euid != p->euid) && (current->euid != p->uid)) {
+ p = NULL;
+ goto out_unlock;
+ }
+ if (p->state == EXIT_ZOMBIE || p->exit_state == EXIT_ZOMBIE) {
+ p = NULL;
+ goto out_unlock;
+ }
+ get_task_struct(p);
+out_unlock:
+ read_unlock(&tasklist_lock);
+
+ return p;
+}
+
+/*
+ * This task is holding PI mutexes at exit time => bad.
+ * Kernel cleans up PI-state, but userspace is likely hosed.
+ * (Robust-futex cleanup is separate and might save the day for userspace.)
+ */
+void exit_pi_state_list(struct task_struct *curr)
+{
+ struct futex_hash_bucket *hb;
+ struct list_head *next, *head = &curr->pi_state_list;
+ struct futex_pi_state *pi_state;
+ union futex_key key;
+
+ /*
+ * We are a ZOMBIE and nobody can enqueue itself on
+ * pi_state_list anymore, but we have to be careful
+ * versus waiters unqueueing themselfs
+ */
+ spin_lock(&curr->pi_lock);
+ while (!list_empty(head)) {
+
+ next = head->next;
+ pi_state = list_entry(next, struct futex_pi_state, list);
+ key = pi_state->key;
+ spin_unlock(&curr->pi_lock);
+
+ hb = hash_futex(&key);
+ spin_lock(&hb->lock);
+
+ spin_lock(&curr->pi_lock);
+ if (head->next != next) {
+ spin_unlock(&hb->lock);
+ continue;
+ }
+
+ list_del_init(&pi_state->list);
+
+ WARN_ON(pi_state->owner != curr);
+
+ pi_state->owner = NULL;
+ spin_unlock(&curr->pi_lock);
+
+ rt_mutex_unlock(&pi_state->pi_mutex);
+
+ spin_unlock(&hb->lock);
+
+ spin_lock(&curr->pi_lock);
+ }
+ spin_unlock(&curr->pi_lock);
+}
+
+static int
+lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, struct futex_q *me)
+{
+ struct futex_pi_state *pi_state = NULL;
+ struct futex_q *this, *next;
+ struct list_head *head;
+ struct task_struct *p;
+ pid_t pid;
+
+ head = &hb->chain;
+
+ list_for_each_entry_safe(this, next, head, list) {
+ if (match_futex (&this->key, &me->key)) {
+ /*
+ * Another waiter already exists - bump up
+ * the refcount and return its pi_state:
+ */
+ pi_state = this->pi_state;
+ atomic_inc(&pi_state->refcount);
+ me->pi_state = pi_state;
+
+ return 0;
+ }
+ }
+ /*
+ * We are the first waiter - try to look up the real owner and
+ * attach the new pi_state to it:
+ */
+ pid = uval & FUTEX_TID_MASK;
+ p = futex_find_get_task(pid);
+ if (!p)
+ return -ESRCH;
+
+ pi_state = alloc_pi_state();
+
+ /*
+ * Initialize the pi_mutex in locked state and make 'p'
+ * the owner of it:
+ */
+ rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p);
+
+ /* Store the key for possible exit cleanups: */
+ pi_state->key = me->key;
+
+ spin_lock(&p->pi_lock);
+ list_add(&pi_state->list, &p->pi_state_list);
+ pi_state->owner = p;
+ spin_unlock(&p->pi_lock);
+
+ put_task_struct(p);
+
+ me->pi_state = pi_state;
+
+ return 0;
+}
+
+/*
* The hash bucket lock must be held when this is called.
* Afterwards, the futex_q must not be accessed.
*/
@@ -286,6 +538,70 @@ static void wake_futex(struct futex_q *q
q->lock_ptr = NULL;
}
+static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
+{
+ struct task_struct *new_owner;
+ struct futex_pi_state *pi_state = this->pi_state;
+ u32 curval, newval;
+
+ if (!pi_state)
+ return -EINVAL;
+
+ new_owner = rt_mutex_next_owner(&pi_state->pi_mutex);
+
+ /*
+ * This happens when we have stolen the lock and the original
+ * pending owner did not enqueue itself back on the rt_mutex.
+ * Thats not a tragedy. We know that way, that a lock waiter
+ * is on the fly. We make the futex_q waiter the pending owner.
+ */
+ if (!new_owner)
+ new_owner = this->task;
+
+ /*
+ * We pass it to the next owner. (The WAITERS bit is always
+ * kept enabled while there is PI state around. We must also
+ * preserve the owner died bit.)
+ */
+ newval = (uval & FUTEX_OWNER_DIED) | FUTEX_WAITERS | new_owner->pid;
+
+ inc_preempt_count();
+ curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval);
+ dec_preempt_count();
+
+ if (curval == -EFAULT)
+ return -EFAULT;
+ if (curval != uval)
+ return -EINVAL;
+
+ list_del_init(&pi_state->owner->pi_state_list);
+ list_add(&pi_state->list, &new_owner->pi_state_list);
+ pi_state->owner = new_owner;
+ rt_mutex_unlock(&pi_state->pi_mutex);
+
+ return 0;
+}
+
+static int unlock_futex_pi(u32 __user *uaddr, u32 uval)
+{
+ u32 oldval;
+
+ /*
+ * There is no waiter, so we unlock the futex. The owner died
+ * bit has not to be preserved here. We are the owner:
+ */
+ inc_preempt_count();
+ oldval = futex_atomic_cmpxchg_inatomic(uaddr, uval, 0);
+ dec_preempt_count();
+
+ if (oldval == -EFAULT)
+ return oldval;
+ if (oldval != uval)
+ return -EAGAIN;
+
+ return 0;
+}
+
/*
* Wake up all waiters hashed on the physical page that is mapped
* to this virtual address:
@@ -310,6 +626,8 @@ static int futex_wake(u32 __user *uaddr,
list_for_each_entry_safe(this, next, head, list) {
if (match_futex (&this->key, &key)) {
+ if (this->pi_state)
+ return -EINVAL;
wake_futex(this);
if (++ret >= nr_wake)
break;
@@ -386,27 +704,9 @@ retry:
* still holding the mmap_sem.
*/
if (attempt++) {
- struct vm_area_struct * vma;
- struct mm_struct *mm = current->mm;
- unsigned long address = (unsigned long)uaddr2;
-
- ret = -EFAULT;
- if (attempt >= 2 ||
- !(vma = find_vma(mm, address)) ||
- vma->vm_start > address ||
- !(vma->vm_flags & VM_WRITE))
+ if (futex_handle_fault((unsigned long)uaddr2,
+ attempt))
goto out;
-
- switch (handle_mm_fault(mm, vma, address, 1)) {
- case VM_FAULT_MINOR:
- current->min_flt++;
- break;
- case VM_FAULT_MAJOR:
- current->maj_flt++;
- break;
- default:
- goto out;
- }
goto retry;
}
@@ -573,6 +873,7 @@ queue_lock(struct futex_q *q, int fd, st
static inline void __queue_me(struct futex_q *q, struct futex_hash_bucket *hb)
{
list_add_tail(&q->list, &hb->chain);
+ q->task = current;
spin_unlock(&hb->lock);
}
@@ -627,6 +928,11 @@ static int unqueue_me(struct futex_q *q)
}
WARN_ON(list_empty(&q->list));
list_del(&q->list);
+
+ if (q->pi_state)
+ free_pi_state(q->pi_state);
+ q->pi_state = NULL;
+
spin_unlock(lock_ptr);
ret = 1;
}
@@ -637,14 +943,16 @@ static int unqueue_me(struct futex_q *q)
static int futex_wait(u32 __user *uaddr, u32 val, unsigned long time)
{
- DECLARE_WAITQUEUE(wait, current);
+ struct task_struct *curr = current;
+ DECLARE_WAITQUEUE(wait, curr);
struct futex_hash_bucket *hb;
struct futex_q q;
u32 uval;
int ret;
+ q.pi_state = NULL;
retry:
- down_read(¤t->mm->mmap_sem);
+ down_read(&curr->mm->mmap_sem);
ret = get_futex_key(uaddr, &q.key);
if (unlikely(ret != 0))
@@ -681,7 +989,7 @@ static int futex_wait(u32 __user *uaddr,
* If we would have faulted, release mmap_sem, fault it in and
* start all over again.
*/
- up_read(¤t->mm->mmap_sem);
+ up_read(&curr->mm->mmap_sem);
ret = get_user(uval, uaddr);
@@ -689,11 +997,9 @@ static int futex_wait(u32 __user *uaddr,
goto retry;
return ret;
}
- if (uval != val) {
- ret = -EWOULDBLOCK;
- queue_unlock(&q, hb);
- goto out_release_sem;
- }
+ ret = -EWOULDBLOCK;
+ if (uval != val)
+ goto out_unlock_release_sem;
/* Only actually queue if *uaddr contained val. */
__queue_me(&q, hb);
@@ -701,8 +1007,8 @@ static int futex_wait(u32 __user *uaddr,
/*
* Now the futex is queued and we have checked the data, we
* don't want to hold mmap_sem while we sleep.
- */
- up_read(¤t->mm->mmap_sem);
+ */
+ up_read(&curr->mm->mmap_sem);
/*
* There might have been scheduling since the queue_me(), as we
@@ -740,8 +1046,306 @@ static int futex_wait(u32 __user *uaddr,
*/
return -EINTR;
+ out_unlock_release_sem:
+ queue_unlock(&q, hb);
+
+ out_release_sem:
+ up_read(&curr->mm->mmap_sem);
+ return ret;
+}
+
+/*
+ * Userspace tried a 0 -> TID atomic transition of the futex value
+ * and failed. The kernel side here does the whole locking operation:
+ * if there are waiters then it will block, it does PI, etc. (Due to
+ * races the kernel might see a 0 value of the futex too.)
+ */
+static int futex_lock_pi(u32 __user *uaddr, int detect,
+ unsigned long sec, long nsec)
+{
+ struct task_struct *curr = current;
+ struct futex_hash_bucket *hb;
+ u32 uval, newval, curval;
+ struct futex_q q;
+ struct hrtimer_sleeper timeout, *to = NULL;
+ int ret, attempt = 0;
+
+ if (refill_pi_state_cache())
+ return -ENOMEM;
+
+ if (sec != MAX_SCHEDULE_TIMEOUT) {
+ to = &timeout;
+ hrtimer_init(&to->timer, CLOCK_REALTIME, HRTIMER_ABS);
+ hrtimer_init_sleeper(to, current);
+ to->timer.expires = ktime_set(sec, nsec);
+ }
+
+ q.pi_state = NULL;
+ retry:
+ down_read(&curr->mm->mmap_sem);
+
+ ret = get_futex_key(uaddr, &q.key);
+ if (unlikely(ret != 0))
+ goto out_release_sem;
+
+ hb = queue_lock(&q, -1, NULL);
+
+ retry_locked:
+ /*
+ * To avoid races, we attempt to take the lock here again
+ * (by doing a 0 -> TID atomic cmpxchg), while holding all
+ * the locks. It will most likely not succeed.
+ */
+ newval = current->pid;
+
+ inc_preempt_count();
+ curval = futex_atomic_cmpxchg_inatomic(uaddr, 0, newval);
+ dec_preempt_count();
+
+ if (unlikely(curval == -EFAULT))
+ goto uaddr_faulted;
+
+ /* We own the lock already */
+ if (unlikely((curval & FUTEX_TID_MASK) == current->pid)) {
+ if (!detect && 0)
+ force_sig(SIGKILL, current);
+ ret = -EDEADLK;
+ goto out_unlock_release_sem;
+ }
+
+ /*
+ * Surprise - we got the lock. Just return
+ * to userspace:
+ */
+ if (unlikely(!curval))
+ goto out_unlock_release_sem;
+
+ uval = curval;
+ newval = uval | FUTEX_WAITERS;
+
+ inc_preempt_count();
+ curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval);
+ dec_preempt_count();
+
+ if (unlikely(curval == -EFAULT))
+ goto uaddr_faulted;
+ if (unlikely(curval != uval))
+ goto retry_locked;
+
+ /*
+ * We dont have the lock. Look up the PI state (or create it if
+ * we are the first waiter):
+ */
+ ret = lookup_pi_state(uval, hb, &q);
+ if (unlikely(ret))
+ goto out_unlock_release_sem;
+
+ /*
+ * Only actually queue now that the atomic ops are done:
+ */
+ __queue_me(&q, hb);
+
+ /*
+ * Now the futex is queued and we have checked the data, we
+ * don't want to hold mmap_sem while we sleep.
+ */
+ up_read(&curr->mm->mmap_sem);
+
+ WARN_ON(!q.pi_state);
+ /*
+ * Block on the PI mutex:
+ */
+ ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1);
+
+ /*
+ * Got the lock. We might not be the anticipated owner if we
+ * did a lock-steal - fix up the PI-state in that case.
+ */
+ if (!ret && q.pi_state->owner != curr) {
+ u32 newtid = current->pid | FUTEX_WAITERS;
+
+ down_read(&curr->mm->mmap_sem);
+ hb = queue_lock(&q, -1, NULL);
+
+ /* Owner died? */
+ if (q.pi_state->owner != NULL) {
+ spin_lock(&q.pi_state->owner->pi_lock);
+ list_del_init(&q.pi_state->list);
+ spin_unlock(&q.pi_state->owner->pi_lock);
+ } else
+ newtid |= FUTEX_OWNER_DIED;
+
+ q.pi_state->owner = current;
+
+ spin_lock(¤t->pi_lock);
+ list_add(&q.pi_state->list, ¤t->pi_state_list);
+ spin_unlock(¤t->pi_lock);
+
+ queue_unlock(&q, hb);
+ up_read(&curr->mm->mmap_sem);
+ /*
+ * We own it, so we have to replace the pending owner
+ * TID. This must be atomic as we have preserve the
+ * owner died bit here.
+ */
+ ret = get_user(uval, uaddr);
+ while (!ret) {
+ newval = (uval & FUTEX_OWNER_DIED) | newtid;
+ curval = futex_atomic_cmpxchg_inatomic(uaddr,
+ uval, newval);
+ if (curval == -EFAULT)
+ ret = -EFAULT;
+ if (curval == uval)
+ break;
+ uval = curval;
+ }
+ }
+
+ unqueue_me(&q);
+
+ if (!detect && ret == -EDEADLK && 0)
+ force_sig(SIGKILL, current);
+
+ return ret;
+
+ out_unlock_release_sem:
+ queue_unlock(&q, hb);
+
out_release_sem:
+ up_read(&curr->mm->mmap_sem);
+ return ret;
+
+ uaddr_faulted:
+ /*
+ * We have to r/w *(int __user *)uaddr, but we can't modify it
+ * non-atomically. Therefore, if get_user below is not
+ * enough, we need to handle the fault ourselves, while
+ * still holding the mmap_sem.
+ */
+ if (attempt++) {
+ if (futex_handle_fault((unsigned long)uaddr, attempt))
+ goto out_unlock_release_sem;
+
+ goto retry_locked;
+ }
+
+ queue_unlock(&q, hb);
+ up_read(&curr->mm->mmap_sem);
+
+ ret = get_user(uval, uaddr);
+ if (!ret && (uval != -EFAULT))
+ goto retry;
+
+ return ret;
+}
+
+/*
+ * Userspace attempted a TID -> 0 atomic transition, and failed.
+ * This is the in-kernel slowpath: we look up the PI state (if any),
+ * and do the rt-mutex unlock.
+ */
+static int futex_unlock_pi(u32 __user *uaddr)
+{
+ struct futex_hash_bucket *hb;
+ struct futex_q *this, *next;
+ u32 uval;
+ struct list_head *head;
+ union futex_key key;
+ int ret, attempt = 0;
+
+retry:
+ if (get_user(uval, uaddr))
+ return -EFAULT;
+ /*
+ * We release only a lock we actually own:
+ */
+ if ((uval & FUTEX_TID_MASK) != current->pid)
+ return -EPERM;
+ /*
+ * First take all the futex related locks:
+ */
+ down_read(¤t->mm->mmap_sem);
+
+ ret = get_futex_key(uaddr, &key);
+ if (unlikely(ret != 0))
+ goto out;
+
+ hb = hash_futex(&key);
+ spin_lock(&hb->lock);
+
+retry_locked:
+ /*
+ * To avoid races, try to do the TID -> 0 atomic transition
+ * again. If it succeeds then we can return without waking
+ * anyone else up:
+ */
+ inc_preempt_count();
+ uval = futex_atomic_cmpxchg_inatomic(uaddr, current->pid, 0);
+ dec_preempt_count();
+
+ if (unlikely(uval == -EFAULT))
+ goto pi_faulted;
+ /*
+ * Rare case: we managed to release the lock atomically,
+ * no need to wake anyone else up:
+ */
+ if (unlikely(uval == current->pid))
+ goto out_unlock;
+
+ /*
+ * Ok, other tasks may need to be woken up - check waiters
+ * and do the wakeup if necessary:
+ */
+ head = &hb->chain;
+
+ list_for_each_entry_safe(this, next, head, list) {
+ if (!match_futex (&this->key, &key))
+ continue;
+ ret = wake_futex_pi(uaddr, uval, this);
+ /*
+ * The atomic access to the futex value
+ * generated a pagefault, so retry the
+ * user-access and the wakeup:
+ */
+ if (ret == -EFAULT)
+ goto pi_faulted;
+ goto out_unlock;
+ }
+ /*
+ * No waiters - kernel unlocks the futex:
+ */
+ ret = unlock_futex_pi(uaddr, uval);
+ if (ret == -EFAULT)
+ goto pi_faulted;
+
+out_unlock:
+ spin_unlock(&hb->lock);
+out:
up_read(¤t->mm->mmap_sem);
+
+ return ret;
+
+pi_faulted:
+ /*
+ * We have to r/w *(int __user *)uaddr, but we can't modify it
+ * non-atomically. Therefore, if get_user below is not
+ * enough, we need to handle the fault ourselves, while
+ * still holding the mmap_sem.
+ */
+ if (attempt++) {
+ if (futex_handle_fault((unsigned long)uaddr, attempt))
+ goto out_unlock;
+
+ goto retry_locked;
+ }
+
+ spin_unlock(&hb->lock);
+ up_read(¤t->mm->mmap_sem);
+
+ ret = get_user(uval, uaddr);
+ if (!ret && (uval != -EFAULT))
+ goto retry;
+
return ret;
}
@@ -820,6 +1424,7 @@ static int futex_fd(u32 __user *uaddr, i
err = -ENOMEM;
goto error;
}
+ q->pi_state = NULL;
down_read(¤t->mm->mmap_sem);
err = get_futex_key(uaddr, &q->key);
@@ -857,7 +1462,7 @@ error:
* Implementation: user-space maintains a per-thread list of locks it
* is holding. Upon do_exit(), the kernel carefully walks this list,
* and marks all locks that are owned by this thread with the
- * FUTEX_OWNER_DEAD bit, and wakes up a waiter (if any). The list is
+ * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is
* always manipulated with the lock held, so the list is private and
* per-thread. Userspace also maintains a per-thread 'list_op_pending'
* field, to allow the kernel to clean up if the thread dies after
@@ -932,7 +1537,7 @@ err_unlock:
*/
int handle_futex_death(u32 __user *uaddr, struct task_struct *curr)
{
- u32 uval;
+ u32 uval, nval;
retry:
if (get_user(uval, uaddr))
@@ -949,8 +1554,12 @@ retry:
* thread-death.) The rest of the cleanup is done in
* userspace.
*/
- if (futex_atomic_cmpxchg_inatomic(uaddr, uval,
- uval | FUTEX_OWNER_DIED) != uval)
+ nval = futex_atomic_cmpxchg_inatomic(uaddr, uval,
+ uval | FUTEX_OWNER_DIED);
+ if (nval == -EFAULT)
+ return -1;
+
+ if (nval != uval)
goto retry;
if (uval & FUTEX_WAITERS)
@@ -995,7 +1604,7 @@ void exit_robust_list(struct task_struct
while (entry != &head->list) {
/*
* A pending lock might already be on the list, so
- * dont process it twice:
+ * don't process it twice:
*/
if (entry != pending)
if (handle_futex_death((void *)entry + futex_offset,
@@ -1041,6 +1650,12 @@ long do_futex(u32 __user *uaddr, int op,
case FUTEX_WAKE_OP:
ret = futex_wake_op(uaddr, uaddr2, val, val2, val3);
break;
+ case FUTEX_LOCK_PI:
+ ret = futex_lock_pi(uaddr, val, timeout, val2);
+ break;
+ case FUTEX_UNLOCK_PI:
+ ret = futex_unlock_pi(uaddr);
+ break;
default:
ret = -ENOSYS;
}
@@ -1056,17 +1671,22 @@ asmlinkage long sys_futex(u32 __user *ua
unsigned long timeout = MAX_SCHEDULE_TIMEOUT;
u32 val2 = 0;
- if (utime && (op == FUTEX_WAIT)) {
+ if (utime && (op == FUTEX_WAIT || op == FUTEX_LOCK_PI)) {
if (copy_from_user(&t, utime, sizeof(t)) != 0)
return -EFAULT;
if (!timespec_valid(&t))
return -EINVAL;
- timeout = timespec_to_jiffies(&t) + 1;
+ if (op == FUTEX_WAIT)
+ timeout = timespec_to_jiffies(&t) + 1;
+ else {
+ timeout = t.tv_sec;
+ val2 = t.tv_nsec;
+ }
}
/*
* requeue parameter in 'utime' if op == FUTEX_REQUEUE.
*/
- if (op >= FUTEX_REQUEUE)
+ if (op == FUTEX_REQUEUE || op == FUTEX_CMP_REQUEUE)
val2 = (u32) (unsigned long) utime;
return do_futex(uaddr, op, val, timeout, uaddr2, val2, val3);
Index: linux-pi-futex.mm.q/kernel/futex_compat.c
===================================================================
--- linux-pi-futex.mm.q.orig/kernel/futex_compat.c
+++ linux-pi-futex.mm.q/kernel/futex_compat.c
@@ -129,14 +129,19 @@ asmlinkage long compat_sys_futex(u32 __u
unsigned long timeout = MAX_SCHEDULE_TIMEOUT;
int val2 = 0;
- if (utime && (op == FUTEX_WAIT)) {
+ if (utime && (op == FUTEX_WAIT || op == FUTEX_LOCK_PI)) {
if (get_compat_timespec(&t, utime))
return -EFAULT;
if (!timespec_valid(&t))
return -EINVAL;
- timeout = timespec_to_jiffies(&t) + 1;
+ if (op == FUTEX_WAIT)
+ timeout = timespec_to_jiffies(&t) + 1;
+ else {
+ timeout = t.tv_sec;
+ val2 = t.tv_nsec;
+ }
}
- if (op >= FUTEX_REQUEUE)
+ if (op == FUTEX_REQUEUE || op == FUTEX_CMP_REQUEUE)
val2 = (int) (unsigned long) utime;
return do_futex(uaddr, op, val, timeout, uaddr2, val2, val3);
-
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