X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=kernel%2Ffutex.c;h=e43945e995f54040aecc49678922b9e18186db52;hb=b331d259b1147f82d692f3b866e036017cbde8fe;hp=f59003b1d8f974be5a39aefb21c989ee5814430a;hpb=627371d73cdd04ed23fe098755b4f855138ad9e0;p=safe%2Fjmp%2Flinux-2.6 diff --git a/kernel/futex.c b/kernel/futex.c index f59003b..e43945e 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -16,6 +16,9 @@ * Copyright (C) 2006 Red Hat, Inc., Ingo Molnar * Copyright (C) 2006 Timesys Corp., Thomas Gleixner * + * PRIVATE futexes by Eric Dumazet + * Copyright (C) 2007 Eric Dumazet + * * 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. @@ -48,37 +51,18 @@ #include #include #include +#include +#include +#include +#include + #include #include "rtmutex_common.h" -#define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8) +int __read_mostly futex_cmpxchg_enabled; -/* - * Futexes are matched on equal values of this key. - * The key type depends on whether it's a shared or private mapping. - * Don't rearrange members without looking at hash_futex(). - * - * offset is aligned to a multiple of sizeof(u32) (== 4) by definition. - * We set bit 0 to indicate if it's an inode-based key. - */ -union futex_key { - struct { - unsigned long pgoff; - struct inode *inode; - int offset; - } shared; - struct { - unsigned long address; - struct mm_struct *mm; - int offset; - } private; - struct { - unsigned long word; - void *ptr; - int offset; - } both; -}; +#define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8) /* * Priority Inheritance state: @@ -106,12 +90,12 @@ struct futex_pi_state { * we can wake only the relevant ones (hashed queues may be shared). * * A futex_q has a woken state, just like tasks have TASK_RUNNING. - * It is considered woken when list_empty(&q->list) || q->lock_ptr == 0. + * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0. * The order of wakup is always to make the first condition true, then * wake up q->waiters, then make the second condition true. */ struct futex_q { - struct list_head list; + struct plist_node list; wait_queue_head_t waiters; /* Which hash list lock to use: */ @@ -127,14 +111,17 @@ struct futex_q { /* Optional priority inheritance state: */ struct futex_pi_state *pi_state; struct task_struct *task; + + /* Bitset for the optional bitmasked wakeup */ + u32 bitset; }; /* * Split the global futex_lock into every hash list lock. */ struct futex_hash_bucket { - spinlock_t lock; - struct list_head chain; + spinlock_t lock; + struct plist_head chain; }; static struct futex_hash_bucket futex_queues[1<mmap_sem, when futex is shared + */ +static inline void futex_lock_mm(struct rw_semaphore *fshared) +{ + if (fshared) + down_read(fshared); +} + +/* + * Release mm->mmap_sem, when the futex is shared + */ +static inline void futex_unlock_mm(struct rw_semaphore *fshared) +{ + if (fshared) + up_read(fshared); +} + +/* * We hash on the keys returned from get_futex_key (see below). */ static struct futex_hash_bucket *hash_futex(union futex_key *key) @@ -163,19 +168,26 @@ static inline int match_futex(union futex_key *key1, union futex_key *key2) && key1->both.offset == key2->both.offset); } -/* - * Get parameters which are the keys for a futex. +/** + * get_futex_key - Get parameters which are the keys for a futex. + * @uaddr: virtual address of the futex + * @shared: NULL for a PROCESS_PRIVATE futex, + * ¤t->mm->mmap_sem for a PROCESS_SHARED futex + * @key: address where result is stored. + * + * Returns a negative error code or 0 + * The key words are stored in *key on success. * - * For shared mappings, it's (page->index, vma->vm_file->f_dentry->d_inode, + * For shared mappings, it's (page->index, vma->vm_file->f_path.dentry->d_inode, * offset_within_page). For private mappings, it's (uaddr, current->mm). * We can usually work out the index without swapping in the page. * - * Returns: 0, or negative error code. - * The key words are stored in *key on success. - * - * Should be called with ¤t->mm->mmap_sem but NOT any spinlocks. + * fshared is NULL for PROCESS_PRIVATE futexes + * For other futexes, it points to ¤t->mm->mmap_sem and + * caller must have taken the reader lock. but NOT any spinlocks. */ -static int get_futex_key(u32 __user *uaddr, union futex_key *key) +static int get_futex_key(u32 __user *uaddr, struct rw_semaphore *fshared, + union futex_key *key) { unsigned long address = (unsigned long)uaddr; struct mm_struct *mm = current->mm; @@ -187,11 +199,25 @@ static int get_futex_key(u32 __user *uaddr, union futex_key *key) * The futex address must be "naturally" aligned. */ key->both.offset = address % PAGE_SIZE; - if (unlikely((key->both.offset % sizeof(u32)) != 0)) + if (unlikely((address % sizeof(u32)) != 0)) return -EINVAL; address -= key->both.offset; /* + * PROCESS_PRIVATE futexes are fast. + * As the mm cannot disappear under us and the 'key' only needs + * virtual address, we dont even have to find the underlying vma. + * Note : We do have to check 'uaddr' is a valid user address, + * but access_ok() should be faster than find_vma() + */ + if (!fshared) { + if (unlikely(!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))) + return -EFAULT; + key->private.mm = mm; + key->private.address = address; + return 0; + } + /* * The futex is hashed differently depending on whether * it's in a shared or private mapping. So check vma first. */ @@ -215,6 +241,7 @@ static int get_futex_key(u32 __user *uaddr, union futex_key *key) * mappings of _writable_ handles. */ if (likely(!(vma->vm_flags & VM_MAYSHARE))) { + key->both.offset |= FUT_OFF_MMSHARED; /* reference taken on mm */ key->private.mm = mm; key->private.address = address; return 0; @@ -223,8 +250,8 @@ static int get_futex_key(u32 __user *uaddr, union futex_key *key) /* * Linear file mappings are also simple. */ - key->shared.inode = vma->vm_file->f_dentry->d_inode; - key->both.offset++; /* Bit 0 of offset indicates inode-based key. */ + key->shared.inode = vma->vm_file->f_path.dentry->d_inode; + key->both.offset |= FUT_OFF_INODE; /* inode-based key. */ if (likely(!(vma->vm_flags & VM_NONLINEAR))) { key->shared.pgoff = (((address - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff); @@ -251,16 +278,18 @@ static int get_futex_key(u32 __user *uaddr, union futex_key *key) * Take a reference to the resource addressed by a key. * Can be called while holding spinlocks. * - * NOTE: mmap_sem MUST be held between get_futex_key() and calling this - * function, if it is called at all. mmap_sem keeps key->shared.inode valid. */ -static inline void get_key_refs(union futex_key *key) +static void get_futex_key_refs(union futex_key *key) { - if (key->both.ptr != 0) { - if (key->both.offset & 1) + if (key->both.ptr == NULL) + return; + switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { + case FUT_OFF_INODE: atomic_inc(&key->shared.inode->i_count); - else + break; + case FUT_OFF_MMSHARED: atomic_inc(&key->private.mm->mm_count); + break; } } @@ -268,50 +297,80 @@ static inline void get_key_refs(union futex_key *key) * Drop a reference to the resource addressed by a key. * The hash bucket spinlock must not be held. */ -static void drop_key_refs(union futex_key *key) +static void drop_futex_key_refs(union futex_key *key) { - if (key->both.ptr != 0) { - if (key->both.offset & 1) + if (!key->both.ptr) + return; + switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { + case FUT_OFF_INODE: iput(key->shared.inode); - else + break; + case FUT_OFF_MMSHARED: mmdrop(key->private.mm); + break; } } -static inline int get_futex_value_locked(u32 *dest, u32 __user *from) +static u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval) +{ + u32 curval; + + pagefault_disable(); + curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval); + pagefault_enable(); + + return curval; +} + +static int get_futex_value_locked(u32 *dest, u32 __user *from) { int ret; - inc_preempt_count(); + pagefault_disable(); ret = __copy_from_user_inatomic(dest, from, sizeof(u32)); - dec_preempt_count(); + pagefault_enable(); return ret ? -EFAULT : 0; } /* - * Fault handling. Called with current->mm->mmap_sem held. + * Fault handling. + * if fshared is non NULL, current->mm->mmap_sem is already held */ -static int futex_handle_fault(unsigned long address, int attempt) +static int futex_handle_fault(unsigned long address, + struct rw_semaphore *fshared, int attempt) { struct vm_area_struct * vma; struct mm_struct *mm = current->mm; + int ret = -EFAULT; - if (attempt >= 2 || !(vma = find_vma(mm, address)) || - vma->vm_start > address || !(vma->vm_flags & VM_WRITE)) - return -EFAULT; + if (attempt > 2) + return ret; - 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; + if (!fshared) + down_read(&mm->mmap_sem); + vma = find_vma(mm, address); + if (vma && address >= vma->vm_start && + (vma->vm_flags & VM_WRITE)) { + int fault; + fault = handle_mm_fault(mm, vma, address, 1); + if (unlikely((fault & VM_FAULT_ERROR))) { +#if 0 + /* XXX: let's do this when we verify it is OK */ + if (ret & VM_FAULT_OOM) + ret = -ENOMEM; +#endif + } else { + ret = 0; + if (fault & VM_FAULT_MAJOR) + current->maj_flt++; + else + current->min_flt++; + } } - return 0; + if (!fshared) + up_read(&mm->mmap_sem); + return ret; } /* @@ -324,12 +383,11 @@ static int refill_pi_state_cache(void) if (likely(current->pi_state_cache)) return 0; - pi_state = kmalloc(sizeof(*pi_state), GFP_KERNEL); + pi_state = kzalloc(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; @@ -389,21 +447,14 @@ 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); + rcu_read_lock(); + p = find_task_by_vpid(pid); + if (!p || ((current->euid != p->euid) && (current->euid != p->uid))) + p = ERR_PTR(-ESRCH); + else + get_task_struct(p); + + rcu_read_unlock(); return p; } @@ -420,6 +471,8 @@ void exit_pi_state_list(struct task_struct *curr) struct futex_hash_bucket *hb; union futex_key key; + if (!futex_cmpxchg_enabled) + return; /* * We are a ZOMBIE and nobody can enqueue itself on * pi_state_list anymore, but we have to be careful @@ -462,18 +515,19 @@ void exit_pi_state_list(struct task_struct *curr) } static int -lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, struct futex_q *me) +lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, + union futex_key *key, struct futex_pi_state **ps) { struct futex_pi_state *pi_state = NULL; struct futex_q *this, *next; - struct list_head *head; + struct plist_head *head; struct task_struct *p; - pid_t pid; + pid_t pid = uval & FUTEX_TID_MASK; head = &hb->chain; - list_for_each_entry_safe(this, next, head, list) { - if (match_futex(&this->key, &me->key)) { + plist_for_each_entry_safe(this, next, head, list) { + if (match_futex(&this->key, key)) { /* * Another waiter already exists - bump up * the refcount and return its pi_state: @@ -486,22 +540,45 @@ lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, struct futex_q *me) return -EINVAL; WARN_ON(!atomic_read(&pi_state->refcount)); + WARN_ON(pid && pi_state->owner && + pi_state->owner->pid != pid); atomic_inc(&pi_state->refcount); - me->pi_state = pi_state; + *ps = pi_state; return 0; } } /* - * We are the first waiter - try to look up the real owner and - * attach the new pi_state to it: + * We are the first waiter - try to look up the real owner and attach + * the new pi_state to it, but bail out when TID = 0 */ - pid = uval & FUTEX_TID_MASK; - p = futex_find_get_task(pid); - if (!p) + if (!pid) return -ESRCH; + p = futex_find_get_task(pid); + if (IS_ERR(p)) + return PTR_ERR(p); + + /* + * We need to look at the task state flags to figure out, + * whether the task is exiting. To protect against the do_exit + * change of the task flags, we do this protected by + * p->pi_lock: + */ + spin_lock_irq(&p->pi_lock); + if (unlikely(p->flags & PF_EXITING)) { + /* + * The task is on the way out. When PF_EXITPIDONE is + * set, we know that the task has finished the + * cleanup: + */ + int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN; + + spin_unlock_irq(&p->pi_lock); + put_task_struct(p); + return ret; + } pi_state = alloc_pi_state(); @@ -512,9 +589,8 @@ lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, struct futex_q *me) rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p); /* Store the key for possible exit cleanups: */ - pi_state->key = me->key; + pi_state->key = *key; - spin_lock_irq(&p->pi_lock); WARN_ON(!list_empty(&pi_state->list)); list_add(&pi_state->list, &p->pi_state_list); pi_state->owner = p; @@ -522,7 +598,7 @@ lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, struct futex_q *me) put_task_struct(p); - me->pi_state = pi_state; + *ps = pi_state; return 0; } @@ -533,12 +609,12 @@ lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, struct futex_q *me) */ static void wake_futex(struct futex_q *q) { - list_del_init(&q->list); + plist_del(&q->list, &q->list.plist); if (q->filp) send_sigio(&q->filp->f_owner, q->fd, POLL_IN); /* * The lock in wake_up_all() is a crucial memory barrier after the - * list_del_init() and also before assigning to q->lock_ptr. + * plist_del() and also before assigning to q->lock_ptr. */ wake_up_all(&q->waiters); /* @@ -550,7 +626,7 @@ static void wake_futex(struct futex_q *q) * at the end of wake_up_all() does not prevent this store from * moving. */ - wmb(); + smp_wmb(); q->lock_ptr = NULL; } @@ -563,6 +639,7 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this) if (!pi_state) return -EINVAL; + spin_lock(&pi_state->pi_mutex.wait_lock); new_owner = rt_mutex_next_owner(&pi_state->pi_mutex); /* @@ -579,16 +656,22 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this) * 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; + if (!(uval & FUTEX_OWNER_DIED)) { + int ret = 0; - inc_preempt_count(); - curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval); - dec_preempt_count(); + newval = FUTEX_WAITERS | task_pid_vnr(new_owner); - if (curval == -EFAULT) - return -EFAULT; - if (curval != uval) - return -EINVAL; + curval = cmpxchg_futex_value_locked(uaddr, uval, newval); + + if (curval == -EFAULT) + ret = -EFAULT; + else if (curval != uval) + ret = -EINVAL; + if (ret) { + spin_unlock(&pi_state->pi_mutex.wait_lock); + return ret; + } + } spin_lock_irq(&pi_state->owner->pi_lock); WARN_ON(list_empty(&pi_state->list)); @@ -601,6 +684,7 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this) pi_state->owner = new_owner; spin_unlock_irq(&new_owner->pi_lock); + spin_unlock(&pi_state->pi_mutex.wait_lock); rt_mutex_unlock(&pi_state->pi_mutex); return 0; @@ -614,9 +698,7 @@ static int unlock_futex_pi(u32 __user *uaddr, u32 uval) * 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(); + oldval = cmpxchg_futex_value_locked(uaddr, uval, 0); if (oldval == -EFAULT) return oldval; @@ -646,17 +728,21 @@ double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) * Wake up all waiters hashed on the physical page that is mapped * to this virtual address: */ -static int futex_wake(u32 __user *uaddr, int nr_wake) +static int futex_wake(u32 __user *uaddr, struct rw_semaphore *fshared, + int nr_wake, u32 bitset) { struct futex_hash_bucket *hb; struct futex_q *this, *next; - struct list_head *head; + struct plist_head *head; union futex_key key; int ret; - down_read(¤t->mm->mmap_sem); + if (!bitset) + return -EINVAL; - ret = get_futex_key(uaddr, &key); + futex_lock_mm(fshared); + + ret = get_futex_key(uaddr, fshared, &key); if (unlikely(ret != 0)) goto out; @@ -664,12 +750,17 @@ static int futex_wake(u32 __user *uaddr, int nr_wake) spin_lock(&hb->lock); head = &hb->chain; - list_for_each_entry_safe(this, next, head, list) { + plist_for_each_entry_safe(this, next, head, list) { if (match_futex (&this->key, &key)) { if (this->pi_state) { ret = -EINVAL; break; } + + /* Check if one of the bits is set in both bitsets */ + if (!(this->bitset & bitset)) + continue; + wake_futex(this); if (++ret >= nr_wake) break; @@ -678,7 +769,7 @@ static int futex_wake(u32 __user *uaddr, int nr_wake) spin_unlock(&hb->lock); out: - up_read(¤t->mm->mmap_sem); + futex_unlock_mm(fshared); return ret; } @@ -687,22 +778,23 @@ out: * to this virtual address: */ static int -futex_wake_op(u32 __user *uaddr1, u32 __user *uaddr2, +futex_wake_op(u32 __user *uaddr1, struct rw_semaphore *fshared, + u32 __user *uaddr2, int nr_wake, int nr_wake2, int op) { union futex_key key1, key2; struct futex_hash_bucket *hb1, *hb2; - struct list_head *head; + struct plist_head *head; struct futex_q *this, *next; int ret, op_ret, attempt = 0; retryfull: - down_read(¤t->mm->mmap_sem); + futex_lock_mm(fshared); - ret = get_futex_key(uaddr1, &key1); + ret = get_futex_key(uaddr1, fshared, &key1); if (unlikely(ret != 0)) goto out; - ret = get_futex_key(uaddr2, &key2); + ret = get_futex_key(uaddr2, fshared, &key2); if (unlikely(ret != 0)) goto out; @@ -742,8 +834,9 @@ retry: * still holding the mmap_sem. */ if (attempt++) { - if (futex_handle_fault((unsigned long)uaddr2, - attempt)) + ret = futex_handle_fault((unsigned long)uaddr2, + fshared, attempt); + if (ret) goto out; goto retry; } @@ -752,7 +845,7 @@ retry: * If we would have faulted, release mmap_sem, * fault it in and start all over again. */ - up_read(¤t->mm->mmap_sem); + futex_unlock_mm(fshared); ret = get_user(dummy, uaddr2); if (ret) @@ -763,7 +856,7 @@ retry: head = &hb1->chain; - list_for_each_entry_safe(this, next, head, list) { + plist_for_each_entry_safe(this, next, head, list) { if (match_futex (&this->key, &key1)) { wake_futex(this); if (++ret >= nr_wake) @@ -775,7 +868,7 @@ retry: head = &hb2->chain; op_ret = 0; - list_for_each_entry_safe(this, next, head, list) { + plist_for_each_entry_safe(this, next, head, list) { if (match_futex (&this->key, &key2)) { wake_futex(this); if (++op_ret >= nr_wake2) @@ -789,7 +882,8 @@ retry: if (hb1 != hb2) spin_unlock(&hb2->lock); out: - up_read(¤t->mm->mmap_sem); + futex_unlock_mm(fshared); + return ret; } @@ -797,22 +891,23 @@ out: * Requeue all waiters hashed on one physical page to another * physical page. */ -static int futex_requeue(u32 __user *uaddr1, u32 __user *uaddr2, +static int futex_requeue(u32 __user *uaddr1, struct rw_semaphore *fshared, + u32 __user *uaddr2, int nr_wake, int nr_requeue, u32 *cmpval) { union futex_key key1, key2; struct futex_hash_bucket *hb1, *hb2; - struct list_head *head1; + struct plist_head *head1; struct futex_q *this, *next; int ret, drop_count = 0; retry: - down_read(¤t->mm->mmap_sem); + futex_lock_mm(fshared); - ret = get_futex_key(uaddr1, &key1); + ret = get_futex_key(uaddr1, fshared, &key1); if (unlikely(ret != 0)) goto out; - ret = get_futex_key(uaddr2, &key2); + ret = get_futex_key(uaddr2, fshared, &key2); if (unlikely(ret != 0)) goto out; @@ -835,7 +930,7 @@ static int futex_requeue(u32 __user *uaddr1, u32 __user *uaddr2, * If we would have faulted, release mmap_sem, fault * it in and start all over again. */ - up_read(¤t->mm->mmap_sem); + futex_unlock_mm(fshared); ret = get_user(curval, uaddr1); @@ -851,7 +946,7 @@ static int futex_requeue(u32 __user *uaddr1, u32 __user *uaddr2, } head1 = &hb1->chain; - list_for_each_entry_safe(this, next, head1, list) { + plist_for_each_entry_safe(this, next, head1, list) { if (!match_futex (&this->key, &key1)) continue; if (++ret <= nr_wake) { @@ -862,11 +957,15 @@ static int futex_requeue(u32 __user *uaddr1, u32 __user *uaddr2, * requeue. */ if (likely(head1 != &hb2->chain)) { - list_move_tail(&this->list, &hb2->chain); + plist_del(&this->list, &hb1->chain); + plist_add(&this->list, &hb2->chain); this->lock_ptr = &hb2->lock; +#ifdef CONFIG_DEBUG_PI_LIST + this->list.plist.lock = &hb2->lock; +#endif } this->key = key2; - get_key_refs(&key2); + get_futex_key_refs(&key2); drop_count++; if (ret - nr_wake >= nr_requeue) @@ -879,12 +978,12 @@ out_unlock: if (hb1 != hb2) spin_unlock(&hb2->lock); - /* drop_key_refs() must be called outside the spinlocks. */ + /* drop_futex_key_refs() must be called outside the spinlocks. */ while (--drop_count >= 0) - drop_key_refs(&key1); + drop_futex_key_refs(&key1); out: - up_read(¤t->mm->mmap_sem); + futex_unlock_mm(fshared); return ret; } @@ -899,7 +998,7 @@ queue_lock(struct futex_q *q, int fd, struct file *filp) init_waitqueue_head(&q->waiters); - get_key_refs(&q->key); + get_futex_key_refs(&q->key); hb = hash_futex(&q->key); q->lock_ptr = &hb->lock; @@ -909,7 +1008,23 @@ queue_lock(struct futex_q *q, int fd, struct file *filp) static inline void __queue_me(struct futex_q *q, struct futex_hash_bucket *hb) { - list_add_tail(&q->list, &hb->chain); + int prio; + + /* + * The priority used to register this element is + * - either the real thread-priority for the real-time threads + * (i.e. threads with a priority lower than MAX_RT_PRIO) + * - or MAX_RT_PRIO for non-RT threads. + * Thus, all RT-threads are woken first in priority order, and + * the others are woken last, in FIFO order. + */ + prio = min(current->normal_prio, MAX_RT_PRIO); + + plist_node_init(&q->list, prio); +#ifdef CONFIG_DEBUG_PI_LIST + q->list.plist.lock = &hb->lock; +#endif + plist_add(&q->list, &hb->chain); q->task = current; spin_unlock(&hb->lock); } @@ -918,7 +1033,7 @@ static inline void queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb) { spin_unlock(&hb->lock); - drop_key_refs(&q->key); + drop_futex_key_refs(&q->key); } /* @@ -944,7 +1059,8 @@ static int unqueue_me(struct futex_q *q) /* In the common case we don't take the spinlock, which is nice. */ retry: lock_ptr = q->lock_ptr; - if (lock_ptr != 0) { + barrier(); + if (lock_ptr != NULL) { spin_lock(lock_ptr); /* * q->lock_ptr can change between reading it and @@ -963,8 +1079,8 @@ static int unqueue_me(struct futex_q *q) spin_unlock(lock_ptr); goto retry; } - WARN_ON(list_empty(&q->list)); - list_del(&q->list); + WARN_ON(plist_node_empty(&q->list)); + plist_del(&q->list, &q->list.plist); BUG_ON(q->pi_state); @@ -972,29 +1088,90 @@ static int unqueue_me(struct futex_q *q) ret = 1; } - drop_key_refs(&q->key); + drop_futex_key_refs(&q->key); return ret; } /* * PI futexes can not be requeued and must remove themself from the - * hash bucket. The hash bucket lock is held on entry and dropped here. + * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry + * and dropped here. */ -static void unqueue_me_pi(struct futex_q *q, struct futex_hash_bucket *hb) +static void unqueue_me_pi(struct futex_q *q) { - WARN_ON(list_empty(&q->list)); - list_del(&q->list); + WARN_ON(plist_node_empty(&q->list)); + plist_del(&q->list, &q->list.plist); BUG_ON(!q->pi_state); free_pi_state(q->pi_state); q->pi_state = NULL; - spin_unlock(&hb->lock); + spin_unlock(q->lock_ptr); + + drop_futex_key_refs(&q->key); +} + +/* + * Fixup the pi_state owner with the new owner. + * + * Must be called with hash bucket lock held and mm->sem held for non + * private futexes. + */ +static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, + struct task_struct *newowner) +{ + u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS; + struct futex_pi_state *pi_state = q->pi_state; + u32 uval, curval, newval; + int ret; + + /* Owner died? */ + if (pi_state->owner != NULL) { + spin_lock_irq(&pi_state->owner->pi_lock); + WARN_ON(list_empty(&pi_state->list)); + list_del_init(&pi_state->list); + spin_unlock_irq(&pi_state->owner->pi_lock); + } else + newtid |= FUTEX_OWNER_DIED; + + pi_state->owner = newowner; + + spin_lock_irq(&newowner->pi_lock); + WARN_ON(!list_empty(&pi_state->list)); + list_add(&pi_state->list, &newowner->pi_state_list); + spin_unlock_irq(&newowner->pi_lock); + + /* + * 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_futex_value_locked(&uval, uaddr); + + while (!ret) { + newval = (uval & FUTEX_OWNER_DIED) | newtid; + + curval = cmpxchg_futex_value_locked(uaddr, uval, newval); - drop_key_refs(&q->key); + if (curval == -EFAULT) + ret = -EFAULT; + if (curval == uval) + break; + uval = curval; + } + return ret; } -static int futex_wait(u32 __user *uaddr, u32 val, unsigned long time) +/* + * In case we must use restart_block to restart a futex_wait, + * we encode in the 'flags' shared capability + */ +#define FLAGS_SHARED 1 + +static long futex_wait_restart(struct restart_block *restart); + +static int futex_wait(u32 __user *uaddr, struct rw_semaphore *fshared, + u32 val, ktime_t *abs_time, u32 bitset) { struct task_struct *curr = current; DECLARE_WAITQUEUE(wait, curr); @@ -1002,12 +1179,18 @@ static int futex_wait(u32 __user *uaddr, u32 val, unsigned long time) struct futex_q q; u32 uval; int ret; + struct hrtimer_sleeper t; + int rem = 0; + + if (!bitset) + return -EINVAL; q.pi_state = NULL; + q.bitset = bitset; retry: - down_read(&curr->mm->mmap_sem); + futex_lock_mm(fshared); - ret = get_futex_key(uaddr, &q.key); + ret = get_futex_key(uaddr, fshared, &q.key); if (unlikely(ret != 0)) goto out_release_sem; @@ -1030,8 +1213,8 @@ static int futex_wait(u32 __user *uaddr, u32 val, unsigned long time) * a wakeup when *uaddr != val on entry to the syscall. This is * rare, but normal. * - * We hold the mmap semaphore, so the mapping cannot have changed - * since we looked it up in get_futex_key. + * for shared futexes, we hold the mmap semaphore, so the mapping + * cannot have changed since we looked it up in get_futex_key. */ ret = get_futex_value_locked(&uval, uaddr); @@ -1042,7 +1225,7 @@ static int futex_wait(u32 __user *uaddr, u32 val, unsigned long time) * If we would have faulted, release mmap_sem, fault it in and * start all over again. */ - up_read(&curr->mm->mmap_sem); + futex_unlock_mm(fshared); ret = get_user(uval, uaddr); @@ -1061,7 +1244,7 @@ static int futex_wait(u32 __user *uaddr, u32 val, unsigned long time) * 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); + futex_unlock_mm(fshared); /* * There might have been scheduling since the queue_me(), as we @@ -1076,11 +1259,35 @@ static int futex_wait(u32 __user *uaddr, u32 val, unsigned long time) __set_current_state(TASK_INTERRUPTIBLE); add_wait_queue(&q.waiters, &wait); /* - * !list_empty() is safe here without any lock. + * !plist_node_empty() is safe here without any lock. * q.lock_ptr != 0 is not safe, because of ordering against wakeup. */ - if (likely(!list_empty(&q.list))) - time = schedule_timeout(time); + if (likely(!plist_node_empty(&q.list))) { + if (!abs_time) + schedule(); + else { + hrtimer_init(&t.timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); + hrtimer_init_sleeper(&t, current); + t.timer.expires = *abs_time; + + hrtimer_start(&t.timer, t.timer.expires, HRTIMER_MODE_ABS); + if (!hrtimer_active(&t.timer)) + t.task = NULL; + + /* + * the timer could have already expired, in which + * case current would be flagged for rescheduling. + * Don't bother calling schedule. + */ + if (likely(t.task)) + schedule(); + + hrtimer_cancel(&t.timer); + + /* Flag if a timeout occured */ + rem = (t.task == NULL); + } + } __set_current_state(TASK_RUNNING); /* @@ -1091,86 +1298,145 @@ static int futex_wait(u32 __user *uaddr, u32 val, unsigned long time) /* If we were woken (and unqueued), we succeeded, whatever. */ if (!unqueue_me(&q)) return 0; - if (time == 0) + if (rem) return -ETIMEDOUT; + /* * We expect signal_pending(current), but another thread may * have handled it for us already. */ - return -EINTR; + if (!abs_time) + return -ERESTARTSYS; + else { + struct restart_block *restart; + restart = ¤t_thread_info()->restart_block; + restart->fn = futex_wait_restart; + restart->futex.uaddr = (u32 *)uaddr; + restart->futex.val = val; + restart->futex.time = abs_time->tv64; + restart->futex.bitset = bitset; + restart->futex.flags = 0; + + if (fshared) + restart->futex.flags |= FLAGS_SHARED; + return -ERESTART_RESTARTBLOCK; + } out_unlock_release_sem: queue_unlock(&q, hb); out_release_sem: - up_read(&curr->mm->mmap_sem); + futex_unlock_mm(fshared); return ret; } + +static long futex_wait_restart(struct restart_block *restart) +{ + u32 __user *uaddr = (u32 __user *)restart->futex.uaddr; + struct rw_semaphore *fshared = NULL; + ktime_t t; + + t.tv64 = restart->futex.time; + restart->fn = do_no_restart_syscall; + if (restart->futex.flags & FLAGS_SHARED) + fshared = ¤t->mm->mmap_sem; + return (long)futex_wait(uaddr, fshared, restart->futex.val, &t, + restart->futex.bitset); +} + + /* * 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 do_futex_lock_pi(u32 __user *uaddr, int detect, int trylock, - struct hrtimer_sleeper *to) +static int futex_lock_pi(u32 __user *uaddr, struct rw_semaphore *fshared, + int detect, ktime_t *time, int trylock) { + struct hrtimer_sleeper timeout, *to = NULL; struct task_struct *curr = current; struct futex_hash_bucket *hb; u32 uval, newval, curval; struct futex_q q; - int ret, attempt = 0; + int ret, lock_taken, ownerdied = 0, attempt = 0; if (refill_pi_state_cache()) return -ENOMEM; + if (time) { + to = &timeout; + hrtimer_init(&to->timer, CLOCK_REALTIME, HRTIMER_MODE_ABS); + hrtimer_init_sleeper(to, current); + to->timer.expires = *time; + } + q.pi_state = NULL; retry: - down_read(&curr->mm->mmap_sem); + futex_lock_mm(fshared); - ret = get_futex_key(uaddr, &q.key); + ret = get_futex_key(uaddr, fshared, &q.key); if (unlikely(ret != 0)) goto out_release_sem; + retry_unlocked: hb = queue_lock(&q, -1, NULL); retry_locked: + ret = lock_taken = 0; + /* * 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; + newval = task_pid_vnr(current); - inc_preempt_count(); - curval = futex_atomic_cmpxchg_inatomic(uaddr, 0, newval); - dec_preempt_count(); + curval = cmpxchg_futex_value_locked(uaddr, 0, newval); 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); + /* + * Detect deadlocks. In case of REQUEUE_PI this is a valid + * situation and we return success to user space. + */ + if (unlikely((curval & FUTEX_TID_MASK) == task_pid_vnr(current))) { ret = -EDEADLK; goto out_unlock_release_sem; } /* - * Surprise - we got the lock. Just return - * to userspace: + * 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(); + /* + * Set the WAITERS flag, so the owner will know it has someone + * to wake at next unlock + */ + newval = curval | FUTEX_WAITERS; + + /* + * There are two cases, where a futex might have no owner (the + * owner TID is 0): OWNER_DIED. We take over the futex in this + * case. We also do an unconditional take over, when the owner + * of the futex died. + * + * This is safe as we are protected by the hash bucket lock ! + */ + if (unlikely(ownerdied || !(curval & FUTEX_TID_MASK))) { + /* Keep the OWNER_DIED bit */ + newval = (curval & ~FUTEX_TID_MASK) | task_pid_vnr(current); + ownerdied = 0; + lock_taken = 1; + } + + curval = cmpxchg_futex_value_locked(uaddr, uval, newval); if (unlikely(curval == -EFAULT)) goto uaddr_faulted; @@ -1178,40 +1444,51 @@ static int do_futex_lock_pi(u32 __user *uaddr, int detect, int trylock, goto retry_locked; /* + * We took the lock due to owner died take over. + */ + if (unlikely(lock_taken)) + goto out_unlock_release_sem; + + /* * 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); + ret = lookup_pi_state(uval, hb, &q.key, &q.pi_state); if (unlikely(ret)) { - /* - * There were no waiters and the owner task lookup - * failed. When the OWNER_DIED bit is set, then we - * know that this is a robust futex and we actually - * take the lock. This is safe as we are protected by - * the hash bucket lock. We also set the waiters bit - * unconditionally here, to simplify glibc handling of - * multiple tasks racing to acquire the lock and - * cleanup the problems which were left by the dead - * owner. - */ - if (curval & FUTEX_OWNER_DIED) { - uval = newval; - newval = current->pid | - FUTEX_OWNER_DIED | FUTEX_WAITERS; + switch (ret) { - inc_preempt_count(); - curval = futex_atomic_cmpxchg_inatomic(uaddr, - uval, newval); - dec_preempt_count(); + case -EAGAIN: + /* + * Task is exiting and we just wait for the + * exit to complete. + */ + queue_unlock(&q, hb); + futex_unlock_mm(fshared); + cond_resched(); + goto retry; - if (unlikely(curval == -EFAULT)) + case -ESRCH: + /* + * No owner found for this futex. Check if the + * OWNER_DIED bit is set to figure out whether + * this is a robust futex or not. + */ + if (get_futex_value_locked(&curval, uaddr)) goto uaddr_faulted; - if (unlikely(curval != uval)) + + /* + * We simply start over in case of a robust + * futex. The code above will take the futex + * and return happy. + */ + if (curval & FUTEX_OWNER_DIED) { + ownerdied = 1; goto retry_locked; - ret = 0; + } + default: + goto out_unlock_release_sem; } - goto out_unlock_release_sem; } /* @@ -1223,7 +1500,7 @@ static int do_futex_lock_pi(u32 __user *uaddr, int detect, int trylock, * 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); + futex_unlock_mm(fshared); WARN_ON(!q.pi_state); /* @@ -1237,76 +1514,80 @@ static int do_futex_lock_pi(u32 __user *uaddr, int detect, int trylock, ret = ret ? 0 : -EWOULDBLOCK; } - down_read(&curr->mm->mmap_sem); + futex_lock_mm(fshared); spin_lock(q.lock_ptr); - /* - * 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; - - /* Owner died? */ - if (q.pi_state->owner != NULL) { - spin_lock_irq(&q.pi_state->owner->pi_lock); - WARN_ON(list_empty(&q.pi_state->list)); - list_del_init(&q.pi_state->list); - spin_unlock_irq(&q.pi_state->owner->pi_lock); - } else - newtid |= FUTEX_OWNER_DIED; - - q.pi_state->owner = current; - - spin_lock_irq(¤t->pi_lock); - WARN_ON(!list_empty(&q.pi_state->list)); - list_add(&q.pi_state->list, ¤t->pi_state_list); - spin_unlock_irq(¤t->pi_lock); - - /* Unqueue and drop the lock */ - unqueue_me_pi(&q, hb); - up_read(&curr->mm->mmap_sem); + if (!ret) { /* - * 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. + * Got the lock. We might not be the anticipated owner + * if we did a lock-steal - fix up the PI-state in + * that case: */ - 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; - } + if (q.pi_state->owner != curr) + ret = fixup_pi_state_owner(uaddr, &q, curr); } else { /* * Catch the rare case, where the lock was released - * when we were on the way back before we locked - * the hash bucket. + * when we were on the way back before we locked the + * hash bucket. */ - if (ret && q.pi_state->owner == curr) { + if (q.pi_state->owner == curr) { + /* + * Try to get the rt_mutex now. This might + * fail as some other task acquired the + * rt_mutex after we removed ourself from the + * rt_mutex waiters list. + */ if (rt_mutex_trylock(&q.pi_state->pi_mutex)) ret = 0; + else { + /* + * pi_state is incorrect, some other + * task did a lock steal and we + * returned due to timeout or signal + * without taking the rt_mutex. Too + * late. We can access the + * rt_mutex_owner without locking, as + * the other task is now blocked on + * the hash bucket lock. Fix the state + * up. + */ + struct task_struct *owner; + int res; + + owner = rt_mutex_owner(&q.pi_state->pi_mutex); + res = fixup_pi_state_owner(uaddr, &q, owner); + + /* propagate -EFAULT, if the fixup failed */ + if (res) + ret = res; + } + } else { + /* + * Paranoia check. If we did not take the lock + * in the trylock above, then we should not be + * the owner of the rtmutex, neither the real + * nor the pending one: + */ + if (rt_mutex_owner(&q.pi_state->pi_mutex) == curr) + printk(KERN_ERR "futex_lock_pi: ret = %d " + "pi-mutex: %p pi-state %p\n", ret, + q.pi_state->pi_mutex.owner, + q.pi_state->owner); } - /* Unqueue and drop the lock */ - unqueue_me_pi(&q, hb); - up_read(&curr->mm->mmap_sem); } - if (!detect && ret == -EDEADLK && 0) - force_sig(SIGKILL, current); + /* Unqueue and drop the lock */ + unqueue_me_pi(&q); + futex_unlock_mm(fshared); - return ret; + return ret != -EINTR ? ret : -ERESTARTNOINTR; out_unlock_release_sem: queue_unlock(&q, hb); out_release_sem: - up_read(&curr->mm->mmap_sem); + futex_unlock_mm(fshared); return ret; uaddr_faulted: @@ -1315,16 +1596,20 @@ static int do_futex_lock_pi(u32 __user *uaddr, int detect, int trylock, * non-atomically. Therefore, if get_user below is not * enough, we need to handle the fault ourselves, while * still holding the mmap_sem. + * + * ... and hb->lock. :-) --ANK */ - if (attempt++) { - if (futex_handle_fault((unsigned long)uaddr, attempt)) - goto out_unlock_release_sem; + queue_unlock(&q, hb); - goto retry_locked; + if (attempt++) { + ret = futex_handle_fault((unsigned long)uaddr, fshared, + attempt); + if (ret) + goto out_release_sem; + goto retry_unlocked; } - queue_unlock(&q, hb); - up_read(&curr->mm->mmap_sem); + futex_unlock_mm(fshared); ret = get_user(uval, uaddr); if (!ret && (uval != -EFAULT)) @@ -1334,86 +1619,16 @@ static int do_futex_lock_pi(u32 __user *uaddr, int detect, int trylock, } /* - * Restart handler - */ -static long futex_lock_pi_restart(struct restart_block *restart) -{ - struct hrtimer_sleeper timeout, *to = NULL; - int ret; - - restart->fn = do_no_restart_syscall; - - if (restart->arg2 || restart->arg3) { - to = &timeout; - hrtimer_init(&to->timer, CLOCK_REALTIME, HRTIMER_ABS); - hrtimer_init_sleeper(to, current); - to->timer.expires.tv64 = ((u64)restart->arg1 << 32) | - (u64) restart->arg0; - } - - pr_debug("lock_pi restart: %p, %d (%d)\n", - (u32 __user *)restart->arg0, current->pid); - - ret = do_futex_lock_pi((u32 __user *)restart->arg0, restart->arg1, - 0, to); - - if (ret != -EINTR) - return ret; - - restart->fn = futex_lock_pi_restart; - - /* The other values are filled in */ - return -ERESTART_RESTARTBLOCK; -} - -/* - * Called from the syscall entry below. - */ -static int futex_lock_pi(u32 __user *uaddr, int detect, unsigned long sec, - long nsec, int trylock) -{ - struct hrtimer_sleeper timeout, *to = NULL; - struct restart_block *restart; - int ret; - - 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); - } - - ret = do_futex_lock_pi(uaddr, detect, trylock, to); - - if (ret != -EINTR) - return ret; - - pr_debug("lock_pi interrupted: %p, %d (%d)\n", uaddr, current->pid); - - restart = ¤t_thread_info()->restart_block; - restart->fn = futex_lock_pi_restart; - restart->arg0 = (unsigned long) uaddr; - restart->arg1 = detect; - if (to) { - restart->arg2 = to->timer.expires.tv64 & 0xFFFFFFFF; - restart->arg3 = to->timer.expires.tv64 >> 32; - } else - restart->arg2 = restart->arg3 = 0; - - return -ERESTART_RESTARTBLOCK; -} - -/* * 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) +static int futex_unlock_pi(u32 __user *uaddr, struct rw_semaphore *fshared) { struct futex_hash_bucket *hb; struct futex_q *this, *next; u32 uval; - struct list_head *head; + struct plist_head *head; union futex_key key; int ret, attempt = 0; @@ -1423,29 +1638,29 @@ retry: /* * We release only a lock we actually own: */ - if ((uval & FUTEX_TID_MASK) != current->pid) + if ((uval & FUTEX_TID_MASK) != task_pid_vnr(current)) return -EPERM; /* * First take all the futex related locks: */ - down_read(¤t->mm->mmap_sem); + futex_lock_mm(fshared); - ret = get_futex_key(uaddr, &key); + ret = get_futex_key(uaddr, fshared, &key); if (unlikely(ret != 0)) goto out; hb = hash_futex(&key); +retry_unlocked: 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 (!(uval & FUTEX_OWNER_DIED)) + uval = cmpxchg_futex_value_locked(uaddr, task_pid_vnr(current), 0); + if (unlikely(uval == -EFAULT)) goto pi_faulted; @@ -1453,7 +1668,7 @@ retry_locked: * Rare case: we managed to release the lock atomically, * no need to wake anyone else up: */ - if (unlikely(uval == current->pid)) + if (unlikely(uval == task_pid_vnr(current))) goto out_unlock; /* @@ -1462,7 +1677,7 @@ retry_locked: */ head = &hb->chain; - list_for_each_entry_safe(this, next, head, list) { + plist_for_each_entry_safe(this, next, head, list) { if (!match_futex (&this->key, &key)) continue; ret = wake_futex_pi(uaddr, uval, this); @@ -1478,14 +1693,16 @@ retry_locked: /* * No waiters - kernel unlocks the futex: */ - ret = unlock_futex_pi(uaddr, uval); - if (ret == -EFAULT) - goto pi_faulted; + if (!(uval & FUTEX_OWNER_DIED)) { + 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); + futex_unlock_mm(fshared); return ret; @@ -1495,16 +1712,21 @@ pi_faulted: * non-atomically. Therefore, if get_user below is not * enough, we need to handle the fault ourselves, while * still holding the mmap_sem. + * + * ... and hb->lock. --ANK */ - if (attempt++) { - if (futex_handle_fault((unsigned long)uaddr, attempt)) - goto out_unlock; + spin_unlock(&hb->lock); - goto retry_locked; + if (attempt++) { + ret = futex_handle_fault((unsigned long)uaddr, fshared, + attempt); + if (ret) + goto out; + uval = 0; + goto retry_unlocked; } - spin_unlock(&hb->lock); - up_read(¤t->mm->mmap_sem); + futex_unlock_mm(fshared); ret = get_user(uval, uaddr); if (!ret && (uval != -EFAULT)) @@ -1533,16 +1755,16 @@ static unsigned int futex_poll(struct file *filp, poll_wait(filp, &q->waiters, wait); /* - * list_empty() is safe here without any lock. + * plist_node_empty() is safe here without any lock. * q->lock_ptr != 0 is not safe, because of ordering against wakeup. */ - if (list_empty(&q->list)) + if (plist_node_empty(&q->list)) ret = POLLIN | POLLRDNORM; return ret; } -static struct file_operations futex_fops = { +static const struct file_operations futex_fops = { .release = futex_close, .poll = futex_poll, }; @@ -1556,6 +1778,14 @@ static int futex_fd(u32 __user *uaddr, int signal) struct futex_q *q; struct file *filp; int ret, err; + struct rw_semaphore *fshared; + static unsigned long printk_interval; + + if (printk_timed_ratelimit(&printk_interval, 60 * 60 * 1000)) { + printk(KERN_WARNING "Process `%s' used FUTEX_FD, which " + "will be removed from the kernel in June 2007\n", + current->comm); + } ret = -EINVAL; if (!valid_signal(signal)) @@ -1571,12 +1801,12 @@ static int futex_fd(u32 __user *uaddr, int signal) goto out; } filp->f_op = &futex_fops; - filp->f_vfsmnt = mntget(futex_mnt); - filp->f_dentry = dget(futex_mnt->mnt_root); - filp->f_mapping = filp->f_dentry->d_inode->i_mapping; + filp->f_path.mnt = mntget(futex_mnt); + filp->f_path.dentry = dget(futex_mnt->mnt_root); + filp->f_mapping = filp->f_path.dentry->d_inode->i_mapping; if (signal) { - err = f_setown(filp, current->pid, 1); + err = __f_setown(filp, task_pid(current), PIDTYPE_PID, 1); if (err < 0) { goto error; } @@ -1590,11 +1820,12 @@ static int futex_fd(u32 __user *uaddr, int signal) } q->pi_state = NULL; - down_read(¤t->mm->mmap_sem); - err = get_futex_key(uaddr, &q->key); + fshared = ¤t->mm->mmap_sem; + down_read(fshared); + err = get_futex_key(uaddr, fshared, &q->key); if (unlikely(err != 0)) { - up_read(¤t->mm->mmap_sem); + up_read(fshared); kfree(q); goto error; } @@ -1606,7 +1837,7 @@ static int futex_fd(u32 __user *uaddr, int signal) filp->private_data = q; queue_me(q, ret, filp); - up_read(¤t->mm->mmap_sem); + up_read(fshared); /* Now we map fd to filp, so userspace can access it */ fd_install(ret, filp); @@ -1643,6 +1874,8 @@ asmlinkage long sys_set_robust_list(struct robust_list_head __user *head, size_t len) { + if (!futex_cmpxchg_enabled) + return -ENOSYS; /* * The kernel knows only one size for now: */ @@ -1661,20 +1894,23 @@ sys_set_robust_list(struct robust_list_head __user *head, * @len_ptr: pointer to a length field, the kernel fills in the header size */ asmlinkage long -sys_get_robust_list(int pid, struct robust_list_head __user **head_ptr, +sys_get_robust_list(int pid, struct robust_list_head __user * __user *head_ptr, size_t __user *len_ptr) { - struct robust_list_head *head; + struct robust_list_head __user *head; unsigned long ret; + if (!futex_cmpxchg_enabled) + return -ENOSYS; + if (!pid) head = current->robust_list; else { struct task_struct *p; ret = -ESRCH; - read_lock(&tasklist_lock); - p = find_task_by_pid(pid); + rcu_read_lock(); + p = find_task_by_vpid(pid); if (!p) goto err_unlock; ret = -EPERM; @@ -1682,7 +1918,7 @@ sys_get_robust_list(int pid, struct robust_list_head __user **head_ptr, !capable(CAP_SYS_PTRACE)) goto err_unlock; head = p->robust_list; - read_unlock(&tasklist_lock); + rcu_read_unlock(); } if (put_user(sizeof(*head), len_ptr)) @@ -1690,7 +1926,7 @@ sys_get_robust_list(int pid, struct robust_list_head __user **head_ptr, return put_user(head, head_ptr); err_unlock: - read_unlock(&tasklist_lock); + rcu_read_unlock(); return ret; } @@ -1699,15 +1935,15 @@ err_unlock: * Process a futex-list entry, check whether it's owned by the * dying task, and do notification if so: */ -int handle_futex_death(u32 __user *uaddr, struct task_struct *curr) +int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi) { - u32 uval, nval; + u32 uval, nval, mval; retry: if (get_user(uval, uaddr)) return -1; - if ((uval & FUTEX_TID_MASK) == curr->pid) { + if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) { /* * Ok, this dying thread is truly holding a futex * of interest. Set the OWNER_DIED bit atomically @@ -1718,21 +1954,45 @@ retry: * thread-death.) The rest of the cleanup is done in * userspace. */ - nval = futex_atomic_cmpxchg_inatomic(uaddr, uval, - uval | FUTEX_OWNER_DIED); + mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED; + nval = futex_atomic_cmpxchg_inatomic(uaddr, uval, mval); + if (nval == -EFAULT) return -1; if (nval != uval) goto retry; - if (uval & FUTEX_WAITERS) - futex_wake(uaddr, 1); + /* + * Wake robust non-PI futexes here. The wakeup of + * PI futexes happens in exit_pi_state(): + */ + if (!pi && (uval & FUTEX_WAITERS)) + futex_wake(uaddr, &curr->mm->mmap_sem, 1, + FUTEX_BITSET_MATCH_ANY); } return 0; } /* + * Fetch a robust-list pointer. Bit 0 signals PI futexes: + */ +static inline int fetch_robust_entry(struct robust_list __user **entry, + struct robust_list __user * __user *head, + int *pi) +{ + unsigned long uentry; + + if (get_user(uentry, (unsigned long __user *)head)) + return -EFAULT; + + *entry = (void __user *)(uentry & ~1UL); + *pi = uentry & 1; + + return 0; +} + +/* * Walk curr->robust_list (very carefully, it's a userspace list!) * and mark any locks found there dead, and notify any waiters. * @@ -1741,15 +2001,19 @@ retry: void exit_robust_list(struct task_struct *curr) { struct robust_list_head __user *head = curr->robust_list; - struct robust_list __user *entry, *pending; - unsigned int limit = ROBUST_LIST_LIMIT; + struct robust_list __user *entry, *next_entry, *pending; + unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip; unsigned long futex_offset; + int rc; + + if (!futex_cmpxchg_enabled) + return; /* * Fetch the list head (which was registered earlier, via * sys_set_robust_list()): */ - if (get_user(entry, &head->list.next)) + if (fetch_robust_entry(&entry, &head->list.next, &pi)) return; /* * Fetch the relative futex offset: @@ -1760,25 +2024,28 @@ void exit_robust_list(struct task_struct *curr) * Fetch any possibly pending lock-add first, and handle it * if it exists: */ - if (get_user(pending, &head->list_op_pending)) + if (fetch_robust_entry(&pending, &head->list_op_pending, &pip)) return; - if (pending) - handle_futex_death((void *)pending + futex_offset, curr); + next_entry = NULL; /* avoid warning with gcc */ while (entry != &head->list) { /* + * Fetch the next entry in the list before calling + * handle_futex_death: + */ + rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi); + /* * A pending lock might already be on the list, so * don't process it twice: */ if (entry != pending) - if (handle_futex_death((void *)entry + futex_offset, - curr)) + if (handle_futex_death((void __user *)entry + futex_offset, + curr, pi)) return; - /* - * Fetch the next entry in the list: - */ - if (get_user(entry, &entry->next)) + if (rc) return; + entry = next_entry; + pi = next_pi; /* * Avoid excessively long or circular lists: */ @@ -1787,41 +2054,57 @@ void exit_robust_list(struct task_struct *curr) cond_resched(); } + + if (pending) + handle_futex_death((void __user *)pending + futex_offset, + curr, pip); } -long do_futex(u32 __user *uaddr, int op, u32 val, unsigned long timeout, +long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout, u32 __user *uaddr2, u32 val2, u32 val3) { - int ret; + int ret = -ENOSYS; + int cmd = op & FUTEX_CMD_MASK; + struct rw_semaphore *fshared = NULL; - switch (op) { + if (!(op & FUTEX_PRIVATE_FLAG)) + fshared = ¤t->mm->mmap_sem; + + switch (cmd) { case FUTEX_WAIT: - ret = futex_wait(uaddr, val, timeout); + val3 = FUTEX_BITSET_MATCH_ANY; + case FUTEX_WAIT_BITSET: + ret = futex_wait(uaddr, fshared, val, timeout, val3); break; case FUTEX_WAKE: - ret = futex_wake(uaddr, val); + val3 = FUTEX_BITSET_MATCH_ANY; + case FUTEX_WAKE_BITSET: + ret = futex_wake(uaddr, fshared, val, val3); break; case FUTEX_FD: /* non-zero val means F_SETOWN(getpid()) & F_SETSIG(val) */ ret = futex_fd(uaddr, val); break; case FUTEX_REQUEUE: - ret = futex_requeue(uaddr, uaddr2, val, val2, NULL); + ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, NULL); break; case FUTEX_CMP_REQUEUE: - ret = futex_requeue(uaddr, uaddr2, val, val2, &val3); + ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3); break; case FUTEX_WAKE_OP: - ret = futex_wake_op(uaddr, uaddr2, val, val2, val3); + ret = futex_wake_op(uaddr, fshared, uaddr2, val, val2, val3); break; case FUTEX_LOCK_PI: - ret = futex_lock_pi(uaddr, val, timeout, val2, 0); + if (futex_cmpxchg_enabled) + ret = futex_lock_pi(uaddr, fshared, val, timeout, 0); break; case FUTEX_UNLOCK_PI: - ret = futex_unlock_pi(uaddr); + if (futex_cmpxchg_enabled) + ret = futex_unlock_pi(uaddr, fshared); break; case FUTEX_TRYLOCK_PI: - ret = futex_lock_pi(uaddr, 0, timeout, val2, 1); + if (futex_cmpxchg_enabled) + ret = futex_lock_pi(uaddr, fshared, 0, timeout, 1); break; default: ret = -ENOSYS; @@ -1834,36 +2117,39 @@ asmlinkage long sys_futex(u32 __user *uaddr, int op, u32 val, struct timespec __user *utime, u32 __user *uaddr2, u32 val3) { - struct timespec t; - unsigned long timeout = MAX_SCHEDULE_TIMEOUT; + struct timespec ts; + ktime_t t, *tp = NULL; u32 val2 = 0; + int cmd = op & FUTEX_CMD_MASK; - if (utime && (op == FUTEX_WAIT || op == FUTEX_LOCK_PI)) { - if (copy_from_user(&t, utime, sizeof(t)) != 0) + if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI || + cmd == FUTEX_WAIT_BITSET)) { + if (copy_from_user(&ts, utime, sizeof(ts)) != 0) return -EFAULT; - if (!timespec_valid(&t)) + if (!timespec_valid(&ts)) return -EINVAL; - if (op == FUTEX_WAIT) - timeout = timespec_to_jiffies(&t) + 1; - else { - timeout = t.tv_sec; - val2 = t.tv_nsec; - } + + t = timespec_to_ktime(ts); + if (cmd == FUTEX_WAIT) + t = ktime_add_safe(ktime_get(), t); + tp = &t; } /* - * requeue parameter in 'utime' if op == FUTEX_REQUEUE. + * requeue parameter in 'utime' if cmd == FUTEX_REQUEUE. + * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP. */ - if (op == FUTEX_REQUEUE || op == FUTEX_CMP_REQUEUE) + if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE || + cmd == FUTEX_WAKE_OP) val2 = (u32) (unsigned long) utime; - return do_futex(uaddr, op, val, timeout, uaddr2, val2, val3); + return do_futex(uaddr, op, val, tp, uaddr2, val2, val3); } static int futexfs_get_sb(struct file_system_type *fs_type, int flags, const char *dev_name, void *data, struct vfsmount *mnt) { - return get_sb_pseudo(fs_type, "futex", NULL, 0xBAD1DEA, mnt); + return get_sb_pseudo(fs_type, "futex", NULL, FUTEXFS_SUPER_MAGIC, mnt); } static struct file_system_type futex_fs_type = { @@ -1872,17 +2158,40 @@ static struct file_system_type futex_fs_type = { .kill_sb = kill_anon_super, }; -static int __init init(void) +static int __init futex_init(void) { - unsigned int i; + u32 curval; + int i; - register_filesystem(&futex_fs_type); - futex_mnt = kern_mount(&futex_fs_type); + /* + * This will fail and we want it. Some arch implementations do + * runtime detection of the futex_atomic_cmpxchg_inatomic() + * functionality. We want to know that before we call in any + * of the complex code paths. Also we want to prevent + * registration of robust lists in that case. NULL is + * guaranteed to fault and we get -EFAULT on functional + * implementation, the non functional ones will return + * -ENOSYS. + */ + curval = cmpxchg_futex_value_locked(NULL, 0, 0); + if (curval == -EFAULT) + futex_cmpxchg_enabled = 1; for (i = 0; i < ARRAY_SIZE(futex_queues); i++) { - INIT_LIST_HEAD(&futex_queues[i].chain); + plist_head_init(&futex_queues[i].chain, &futex_queues[i].lock); spin_lock_init(&futex_queues[i].lock); } + + i = register_filesystem(&futex_fs_type); + if (i) + return i; + + futex_mnt = kern_mount(&futex_fs_type); + if (IS_ERR(futex_mnt)) { + unregister_filesystem(&futex_fs_type); + return PTR_ERR(futex_mnt); + } + return 0; } -__initcall(init); +__initcall(futex_init);