#include <linux/nsproxy.h>
#include <linux/ptrace.h>
#include <linux/sched/rt.h>
+#include <linux/hugetlb.h>
+#include <linux/freezer.h>
+#include <linux/bootmem.h>
+#include <linux/fault-inject.h>
#include <asm/futex.h>
-#include "rtmutex_common.h"
+#include "locking/rtmutex_common.h"
-int __read_mostly futex_cmpxchg_enabled;
+/*
+ * READ this before attempting to hack on futexes!
+ *
+ * Basic futex operation and ordering guarantees
+ * =============================================
+ *
+ * The waiter reads the futex value in user space and calls
+ * futex_wait(). This function computes the hash bucket and acquires
+ * the hash bucket lock. After that it reads the futex user space value
+ * again and verifies that the data has not changed. If it has not changed
+ * it enqueues itself into the hash bucket, releases the hash bucket lock
+ * and schedules.
+ *
+ * The waker side modifies the user space value of the futex and calls
+ * futex_wake(). This function computes the hash bucket and acquires the
+ * hash bucket lock. Then it looks for waiters on that futex in the hash
+ * bucket and wakes them.
+ *
+ * In futex wake up scenarios where no tasks are blocked on a futex, taking
+ * the hb spinlock can be avoided and simply return. In order for this
+ * optimization to work, ordering guarantees must exist so that the waiter
+ * being added to the list is acknowledged when the list is concurrently being
+ * checked by the waker, avoiding scenarios like the following:
+ *
+ * CPU 0 CPU 1
+ * val = *futex;
+ * sys_futex(WAIT, futex, val);
+ * futex_wait(futex, val);
+ * uval = *futex;
+ * *futex = newval;
+ * sys_futex(WAKE, futex);
+ * futex_wake(futex);
+ * if (queue_empty())
+ * return;
+ * if (uval == val)
+ * lock(hash_bucket(futex));
+ * queue();
+ * unlock(hash_bucket(futex));
+ * schedule();
+ *
+ * This would cause the waiter on CPU 0 to wait forever because it
+ * missed the transition of the user space value from val to newval
+ * and the waker did not find the waiter in the hash bucket queue.
+ *
+ * The correct serialization ensures that a waiter either observes
+ * the changed user space value before blocking or is woken by a
+ * concurrent waker:
+ *
+ * CPU 0 CPU 1
+ * val = *futex;
+ * sys_futex(WAIT, futex, val);
+ * futex_wait(futex, val);
+ *
+ * waiters++; (a)
+ * mb(); (A) <-- paired with -.
+ * |
+ * lock(hash_bucket(futex)); |
+ * |
+ * uval = *futex; |
+ * | *futex = newval;
+ * | sys_futex(WAKE, futex);
+ * | futex_wake(futex);
+ * |
+ * `-------> mb(); (B)
+ * if (uval == val)
+ * queue();
+ * unlock(hash_bucket(futex));
+ * schedule(); if (waiters)
+ * lock(hash_bucket(futex));
+ * else wake_waiters(futex);
+ * waiters--; (b) unlock(hash_bucket(futex));
+ *
+ * Where (A) orders the waiters increment and the futex value read through
+ * atomic operations (see hb_waiters_inc) and where (B) orders the write
+ * to futex and the waiters read -- this is done by the barriers for both
+ * shared and private futexes in get_futex_key_refs().
+ *
+ * This yields the following case (where X:=waiters, Y:=futex):
+ *
+ * X = Y = 0
+ *
+ * w[X]=1 w[Y]=1
+ * MB MB
+ * r[Y]=y r[X]=x
+ *
+ * Which guarantees that x==0 && y==0 is impossible; which translates back into
+ * the guarantee that we cannot both miss the futex variable change and the
+ * enqueue.
+ *
+ * Note that a new waiter is accounted for in (a) even when it is possible that
+ * the wait call can return error, in which case we backtrack from it in (b).
+ * Refer to the comment in queue_lock().
+ *
+ * Similarly, in order to account for waiters being requeued on another
+ * address we always increment the waiters for the destination bucket before
+ * acquiring the lock. It then decrements them again after releasing it -
+ * the code that actually moves the futex(es) between hash buckets (requeue_futex)
+ * will do the additional required waiter count housekeeping. This is done for
+ * double_lock_hb() and double_unlock_hb(), respectively.
+ */
-#define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
+#ifndef CONFIG_HAVE_FUTEX_CMPXCHG
+int __read_mostly futex_cmpxchg_enabled;
+#endif
/*
* Futex flags used to encode options to functions and preserve them across
* waiting on a futex.
*/
struct futex_hash_bucket {
+ atomic_t waiters;
spinlock_t lock;
struct plist_head chain;
+} ____cacheline_aligned_in_smp;
+
+/*
+ * The base of the bucket array and its size are always used together
+ * (after initialization only in hash_futex()), so ensure that they
+ * reside in the same cacheline.
+ */
+static struct {
+ struct futex_hash_bucket *queues;
+ unsigned long hashsize;
+} __futex_data __read_mostly __aligned(2*sizeof(long));
+#define futex_queues (__futex_data.queues)
+#define futex_hashsize (__futex_data.hashsize)
+
+
+/*
+ * Fault injections for futexes.
+ */
+#ifdef CONFIG_FAIL_FUTEX
+
+static struct {
+ struct fault_attr attr;
+
+ bool ignore_private;
+} fail_futex = {
+ .attr = FAULT_ATTR_INITIALIZER,
+ .ignore_private = false,
};
-static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS];
+static int __init setup_fail_futex(char *str)
+{
+ return setup_fault_attr(&fail_futex.attr, str);
+}
+__setup("fail_futex=", setup_fail_futex);
+
+static bool should_fail_futex(bool fshared)
+{
+ if (fail_futex.ignore_private && !fshared)
+ return false;
+
+ return should_fail(&fail_futex.attr, 1);
+}
+
+#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
+
+static int __init fail_futex_debugfs(void)
+{
+ umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
+ struct dentry *dir;
+
+ dir = fault_create_debugfs_attr("fail_futex", NULL,
+ &fail_futex.attr);
+ if (IS_ERR(dir))
+ return PTR_ERR(dir);
+
+ if (!debugfs_create_bool("ignore-private", mode, dir,
+ &fail_futex.ignore_private)) {
+ debugfs_remove_recursive(dir);
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+late_initcall(fail_futex_debugfs);
+
+#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
+
+#else
+static inline bool should_fail_futex(bool fshared)
+{
+ return false;
+}
+#endif /* CONFIG_FAIL_FUTEX */
+
+static inline void futex_get_mm(union futex_key *key)
+{
+ atomic_inc(&key->private.mm->mm_count);
+ /*
+ * Ensure futex_get_mm() implies a full barrier such that
+ * get_futex_key() implies a full barrier. This is relied upon
+ * as full barrier (B), see the ordering comment above.
+ */
+ smp_mb__after_atomic();
+}
+
+/*
+ * Reflects a new waiter being added to the waitqueue.
+ */
+static inline void hb_waiters_inc(struct futex_hash_bucket *hb)
+{
+#ifdef CONFIG_SMP
+ atomic_inc(&hb->waiters);
+ /*
+ * Full barrier (A), see the ordering comment above.
+ */
+ smp_mb__after_atomic();
+#endif
+}
+
+/*
+ * Reflects a waiter being removed from the waitqueue by wakeup
+ * paths.
+ */
+static inline void hb_waiters_dec(struct futex_hash_bucket *hb)
+{
+#ifdef CONFIG_SMP
+ atomic_dec(&hb->waiters);
+#endif
+}
+
+static inline int hb_waiters_pending(struct futex_hash_bucket *hb)
+{
+#ifdef CONFIG_SMP
+ return atomic_read(&hb->waiters);
+#else
+ return 1;
+#endif
+}
/*
* We hash on the keys returned from get_futex_key (see below).
u32 hash = jhash2((u32*)&key->both.word,
(sizeof(key->both.word)+sizeof(key->both.ptr))/4,
key->both.offset);
- return &futex_queues[hash & ((1 << FUTEX_HASHBITS)-1)];
+ return &futex_queues[hash & (futex_hashsize - 1)];
}
/*
switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
case FUT_OFF_INODE:
- ihold(key->shared.inode);
+ ihold(key->shared.inode); /* implies MB (B) */
break;
case FUT_OFF_MMSHARED:
- atomic_inc(&key->private.mm->mm_count);
+ futex_get_mm(key); /* implies MB (B) */
break;
+ default:
+ /*
+ * Private futexes do not hold reference on an inode or
+ * mm, therefore the only purpose of calling get_futex_key_refs
+ * is because we need the barrier for the lockless waiter check.
+ */
+ smp_mb(); /* explicit MB (B) */
}
}
/*
* Drop a reference to the resource addressed by a key.
- * The hash bucket spinlock must not be held.
+ * The hash bucket spinlock must not be held. This is
+ * a no-op for private futexes, see comment in the get
+ * counterpart.
*/
static void drop_futex_key_refs(union futex_key *key)
{
return -EINVAL;
address -= key->both.offset;
+ if (unlikely(!access_ok(rw, uaddr, sizeof(u32))))
+ return -EFAULT;
+
+ if (unlikely(should_fail_futex(fshared)))
+ return -EFAULT;
+
/*
* PROCESS_PRIVATE futexes are fast.
* As the mm cannot disappear under us and the 'key' only needs
* 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;
- get_futex_key_refs(key);
+ get_futex_key_refs(key); /* implies MB (B) */
return 0;
}
again:
+ /* Ignore any VERIFY_READ mapping (futex common case) */
+ if (unlikely(should_fail_futex(fshared)))
+ return -EFAULT;
+
err = get_user_pages_fast(address, 1, 1, &page);
/*
* If write access is not required (eg. FUTEX_WAIT), try
put_page(page);
/* serialize against __split_huge_page_splitting() */
local_irq_disable();
- if (likely(__get_user_pages_fast(address, 1, 1, &page) == 1)) {
+ if (likely(__get_user_pages_fast(address, 1, !ro, &page) == 1)) {
page_head = compound_head(page);
/*
* page_head is valid pointer but we must pin
* A RO anonymous page will never change and thus doesn't make
* sense for futex operations.
*/
- if (ro) {
+ if (unlikely(should_fail_futex(fshared)) || ro) {
err = -EFAULT;
goto out;
}
} else {
key->both.offset |= FUT_OFF_INODE; /* inode-based key */
key->shared.inode = page_head->mapping->host;
- key->shared.pgoff = page_head->index;
+ key->shared.pgoff = basepage_index(page);
}
- get_futex_key_refs(key);
+ get_futex_key_refs(key); /* implies MB (B) */
out:
unlock_page(page_head);
return pi_state;
}
+/*
+ * Must be called with the hb lock held.
+ */
static void free_pi_state(struct futex_pi_state *pi_state)
{
+ if (!pi_state)
+ return;
+
if (!atomic_dec_and_test(&pi_state->refcount))
return;
raw_spin_unlock_irq(&curr->pi_lock);
}
-static int
-lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
- union futex_key *key, struct futex_pi_state **ps)
+/*
+ * We need to check the following states:
+ *
+ * Waiter | pi_state | pi->owner | uTID | uODIED | ?
+ *
+ * [1] NULL | --- | --- | 0 | 0/1 | Valid
+ * [2] NULL | --- | --- | >0 | 0/1 | Valid
+ *
+ * [3] Found | NULL | -- | Any | 0/1 | Invalid
+ *
+ * [4] Found | Found | NULL | 0 | 1 | Valid
+ * [5] Found | Found | NULL | >0 | 1 | Invalid
+ *
+ * [6] Found | Found | task | 0 | 1 | Valid
+ *
+ * [7] Found | Found | NULL | Any | 0 | Invalid
+ *
+ * [8] Found | Found | task | ==taskTID | 0/1 | Valid
+ * [9] Found | Found | task | 0 | 0 | Invalid
+ * [10] Found | Found | task | !=taskTID | 0/1 | Invalid
+ *
+ * [1] Indicates that the kernel can acquire the futex atomically. We
+ * came came here due to a stale FUTEX_WAITERS/FUTEX_OWNER_DIED bit.
+ *
+ * [2] Valid, if TID does not belong to a kernel thread. If no matching
+ * thread is found then it indicates that the owner TID has died.
+ *
+ * [3] Invalid. The waiter is queued on a non PI futex
+ *
+ * [4] Valid state after exit_robust_list(), which sets the user space
+ * value to FUTEX_WAITERS | FUTEX_OWNER_DIED.
+ *
+ * [5] The user space value got manipulated between exit_robust_list()
+ * and exit_pi_state_list()
+ *
+ * [6] Valid state after exit_pi_state_list() which sets the new owner in
+ * the pi_state but cannot access the user space value.
+ *
+ * [7] pi_state->owner can only be NULL when the OWNER_DIED bit is set.
+ *
+ * [8] Owner and user space value match
+ *
+ * [9] There is no transient state which sets the user space TID to 0
+ * except exit_robust_list(), but this is indicated by the
+ * FUTEX_OWNER_DIED bit. See [4]
+ *
+ * [10] There is no transient state which leaves owner and user space
+ * TID out of sync.
+ */
+
+/*
+ * Validate that the existing waiter has a pi_state and sanity check
+ * the pi_state against the user space value. If correct, attach to
+ * it.
+ */
+static int attach_to_pi_state(u32 uval, struct futex_pi_state *pi_state,
+ struct futex_pi_state **ps)
{
- struct futex_pi_state *pi_state = NULL;
- struct futex_q *this, *next;
- struct plist_head *head;
- struct task_struct *p;
pid_t pid = uval & FUTEX_TID_MASK;
- head = &hb->chain;
+ /*
+ * Userspace might have messed up non-PI and PI futexes [3]
+ */
+ if (unlikely(!pi_state))
+ return -EINVAL;
- 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:
- */
- pi_state = this->pi_state;
+ WARN_ON(!atomic_read(&pi_state->refcount));
+
+ /*
+ * Handle the owner died case:
+ */
+ if (uval & FUTEX_OWNER_DIED) {
+ /*
+ * exit_pi_state_list sets owner to NULL and wakes the
+ * topmost waiter. The task which acquires the
+ * pi_state->rt_mutex will fixup owner.
+ */
+ if (!pi_state->owner) {
/*
- * Userspace might have messed up non-PI and PI futexes
+ * No pi state owner, but the user space TID
+ * is not 0. Inconsistent state. [5]
*/
- if (unlikely(!pi_state))
+ if (pid)
return -EINVAL;
-
- WARN_ON(!atomic_read(&pi_state->refcount));
-
/*
- * When pi_state->owner is NULL then the owner died
- * and another waiter is on the fly. pi_state->owner
- * is fixed up by the task which acquires
- * pi_state->rt_mutex.
- *
- * We do not check for pid == 0 which can happen when
- * the owner died and robust_list_exit() cleared the
- * TID.
+ * Take a ref on the state and return success. [4]
*/
- if (pid && pi_state->owner) {
- /*
- * Bail out if user space manipulated the
- * futex value.
- */
- if (pid != task_pid_vnr(pi_state->owner))
- return -EINVAL;
- }
-
- atomic_inc(&pi_state->refcount);
- *ps = pi_state;
-
- return 0;
+ goto out_state;
}
+
+ /*
+ * If TID is 0, then either the dying owner has not
+ * yet executed exit_pi_state_list() or some waiter
+ * acquired the rtmutex in the pi state, but did not
+ * yet fixup the TID in user space.
+ *
+ * Take a ref on the state and return success. [6]
+ */
+ if (!pid)
+ goto out_state;
+ } else {
+ /*
+ * If the owner died bit is not set, then the pi_state
+ * must have an owner. [7]
+ */
+ if (!pi_state->owner)
+ return -EINVAL;
}
+ /*
+ * Bail out if user space manipulated the futex value. If pi
+ * state exists then the owner TID must be the same as the
+ * user space TID. [9/10]
+ */
+ if (pid != task_pid_vnr(pi_state->owner))
+ return -EINVAL;
+out_state:
+ atomic_inc(&pi_state->refcount);
+ *ps = pi_state;
+ return 0;
+}
+
+/*
+ * Lookup the task for the TID provided from user space and attach to
+ * it after doing proper sanity checks.
+ */
+static int attach_to_pi_owner(u32 uval, union futex_key *key,
+ struct futex_pi_state **ps)
+{
+ pid_t pid = uval & FUTEX_TID_MASK;
+ struct futex_pi_state *pi_state;
+ struct task_struct *p;
+
/*
* 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
+ * the new pi_state to it, but bail out when TID = 0 [1]
*/
if (!pid)
return -ESRCH;
if (!p)
return -ESRCH;
+ if (unlikely(p->flags & PF_KTHREAD)) {
+ put_task_struct(p);
+ return -EPERM;
+ }
+
/*
* We need to look at the task state flags to figure out,
* whether the task is exiting. To protect against the do_exit
return ret;
}
+ /*
+ * No existing pi state. First waiter. [2]
+ */
pi_state = alloc_pi_state();
/*
- * Initialize the pi_mutex in locked state and make 'p'
+ * Initialize the pi_mutex in locked state and make @p
* the owner of it:
*/
rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p);
return 0;
}
+static int lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
+ union futex_key *key, struct futex_pi_state **ps)
+{
+ struct futex_q *match = futex_top_waiter(hb, key);
+
+ /*
+ * If there is a waiter on that futex, validate it and
+ * attach to the pi_state when the validation succeeds.
+ */
+ if (match)
+ return attach_to_pi_state(uval, match->pi_state, ps);
+
+ /*
+ * We are the first waiter - try to look up the owner based on
+ * @uval and attach to it.
+ */
+ return attach_to_pi_owner(uval, key, ps);
+}
+
+static int lock_pi_update_atomic(u32 __user *uaddr, u32 uval, u32 newval)
+{
+ u32 uninitialized_var(curval);
+
+ if (unlikely(should_fail_futex(true)))
+ return -EFAULT;
+
+ if (unlikely(cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)))
+ return -EFAULT;
+
+ /*If user space value changed, let the caller retry */
+ return curval != uval ? -EAGAIN : 0;
+}
+
/**
* futex_lock_pi_atomic() - Atomic work required to acquire a pi aware futex
* @uaddr: the pi futex user address
struct futex_pi_state **ps,
struct task_struct *task, int set_waiters)
{
- int lock_taken, ret, force_take = 0;
- u32 uval, newval, curval, vpid = task_pid_vnr(task);
-
-retry:
- ret = lock_taken = 0;
+ u32 uval, newval, vpid = task_pid_vnr(task);
+ struct futex_q *match;
+ int ret;
/*
- * 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.
+ * Read the user space value first so we can validate a few
+ * things before proceeding further.
*/
- newval = vpid;
- if (set_waiters)
- newval |= FUTEX_WAITERS;
+ if (get_futex_value_locked(&uval, uaddr))
+ return -EFAULT;
- if (unlikely(cmpxchg_futex_value_locked(&curval, uaddr, 0, newval)))
+ if (unlikely(should_fail_futex(true)))
return -EFAULT;
/*
* Detect deadlocks.
*/
- if ((unlikely((curval & FUTEX_TID_MASK) == vpid)))
+ if ((unlikely((uval & FUTEX_TID_MASK) == vpid)))
return -EDEADLK;
- /*
- * Surprise - we got the lock. Just return to userspace:
- */
- if (unlikely(!curval))
- return 1;
-
- uval = curval;
+ if ((unlikely(should_fail_futex(true))))
+ return -EDEADLK;
/*
- * Set the FUTEX_WAITERS flag, so the owner will know it has someone
- * to wake at the next unlock.
+ * Lookup existing state first. If it exists, try to attach to
+ * its pi_state.
*/
- newval = curval | FUTEX_WAITERS;
+ match = futex_top_waiter(hb, key);
+ if (match)
+ return attach_to_pi_state(uval, match->pi_state, ps);
/*
- * Should we force take the futex? See below.
+ * No waiter and user TID is 0. We are here because the
+ * waiters or the owner died bit is set or called from
+ * requeue_cmp_pi or for whatever reason something took the
+ * syscall.
*/
- if (unlikely(force_take)) {
+ if (!(uval & FUTEX_TID_MASK)) {
/*
- * Keep the OWNER_DIED and the WAITERS bit and set the
- * new TID value.
+ * We take over the futex. No other waiters and the user space
+ * TID is 0. We preserve the owner died bit.
*/
- newval = (curval & ~FUTEX_TID_MASK) | vpid;
- force_take = 0;
- lock_taken = 1;
- }
+ newval = uval & FUTEX_OWNER_DIED;
+ newval |= vpid;
- if (unlikely(cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)))
- return -EFAULT;
- if (unlikely(curval != uval))
- goto retry;
+ /* The futex requeue_pi code can enforce the waiters bit */
+ if (set_waiters)
+ newval |= FUTEX_WAITERS;
+
+ ret = lock_pi_update_atomic(uaddr, uval, newval);
+ /* If the take over worked, return 1 */
+ return ret < 0 ? ret : 1;
+ }
/*
- * We took the lock due to forced take over.
+ * First waiter. Set the waiters bit before attaching ourself to
+ * the owner. If owner tries to unlock, it will be forced into
+ * the kernel and blocked on hb->lock.
*/
- if (unlikely(lock_taken))
- return 1;
-
+ newval = uval | FUTEX_WAITERS;
+ ret = lock_pi_update_atomic(uaddr, uval, newval);
+ if (ret)
+ return ret;
/*
- * We dont have the lock. Look up the PI state (or create it if
- * we are the first waiter):
+ * If the update of the user space value succeeded, we try to
+ * attach to the owner. If that fails, no harm done, we only
+ * set the FUTEX_WAITERS bit in the user space variable.
*/
- ret = lookup_pi_state(uval, hb, key, ps);
-
- if (unlikely(ret)) {
- switch (ret) {
- case -ESRCH:
- /*
- * We failed to find an owner for this
- * futex. So we have no pi_state to block
- * on. This can happen in two cases:
- *
- * 1) The owner died
- * 2) A stale FUTEX_WAITERS bit
- *
- * Re-read the futex value.
- */
- if (get_futex_value_locked(&curval, uaddr))
- return -EFAULT;
-
- /*
- * If the owner died or we have a stale
- * WAITERS bit the owner TID in the user space
- * futex is 0.
- */
- if (!(curval & FUTEX_TID_MASK)) {
- force_take = 1;
- goto retry;
- }
- default:
- break;
- }
- }
-
- return ret;
+ return attach_to_pi_owner(uval, key, ps);
}
/**
hb = container_of(q->lock_ptr, struct futex_hash_bucket, lock);
plist_del(&q->list, &hb->chain);
+ hb_waiters_dec(hb);
}
/*
* The hash bucket lock must be held when this is called.
- * Afterwards, the futex_q must not be accessed.
+ * Afterwards, the futex_q must not be accessed. Callers
+ * must ensure to later call wake_up_q() for the actual
+ * wakeups to occur.
*/
-static void wake_futex(struct futex_q *q)
+static void mark_wake_futex(struct wake_q_head *wake_q, struct futex_q *q)
{
struct task_struct *p = q->task;
return;
/*
- * We set q->lock_ptr = NULL _before_ we wake up the task. If
- * a non-futex wake up happens on another CPU then the task
- * might exit and p would dereference a non-existing task
- * struct. Prevent this by holding a reference on p across the
- * wake up.
+ * Queue the task for later wakeup for after we've released
+ * the hb->lock. wake_q_add() grabs reference to p.
*/
- get_task_struct(p);
-
+ wake_q_add(wake_q, p);
__unqueue_futex(q);
/*
* The waiting task can free the futex_q as soon as
*/
smp_wmb();
q->lock_ptr = NULL;
-
- wake_up_state(p, TASK_NORMAL);
- put_task_struct(p);
}
-static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
+static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this,
+ struct futex_hash_bucket *hb)
{
struct task_struct *new_owner;
struct futex_pi_state *pi_state = this->pi_state;
u32 uninitialized_var(curval), newval;
+ WAKE_Q(wake_q);
+ bool deboost;
+ int ret = 0;
if (!pi_state)
return -EINVAL;
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.)
+ * We pass it to the next owner. The WAITERS bit is always
+ * kept enabled while there is PI state around. We cleanup the
+ * owner died bit, because we are the owner.
*/
- if (!(uval & FUTEX_OWNER_DIED)) {
- int ret = 0;
+ newval = FUTEX_WAITERS | task_pid_vnr(new_owner);
- newval = FUTEX_WAITERS | task_pid_vnr(new_owner);
+ if (unlikely(should_fail_futex(true)))
+ ret = -EFAULT;
- if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval))
- ret = -EFAULT;
- else if (curval != uval)
+ if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)) {
+ ret = -EFAULT;
+ } else if (curval != uval) {
+ /*
+ * If a unconditional UNLOCK_PI operation (user space did not
+ * try the TID->0 transition) raced with a waiter setting the
+ * FUTEX_WAITERS flag between get_user() and locking the hash
+ * bucket lock, retry the operation.
+ */
+ if ((FUTEX_TID_MASK & curval) == uval)
+ ret = -EAGAIN;
+ else
ret = -EINVAL;
- if (ret) {
- raw_spin_unlock(&pi_state->pi_mutex.wait_lock);
- return ret;
- }
+ }
+ if (ret) {
+ raw_spin_unlock(&pi_state->pi_mutex.wait_lock);
+ return ret;
}
raw_spin_lock_irq(&pi_state->owner->pi_lock);
raw_spin_unlock_irq(&new_owner->pi_lock);
raw_spin_unlock(&pi_state->pi_mutex.wait_lock);
- rt_mutex_unlock(&pi_state->pi_mutex);
- return 0;
-}
-
-static int unlock_futex_pi(u32 __user *uaddr, u32 uval)
-{
- u32 uninitialized_var(oldval);
+ deboost = rt_mutex_futex_unlock(&pi_state->pi_mutex, &wake_q);
/*
- * There is no waiter, so we unlock the futex. The owner died
- * bit has not to be preserved here. We are the owner:
+ * First unlock HB so the waiter does not spin on it once he got woken
+ * up. Second wake up the waiter before the priority is adjusted. If we
+ * deboost first (and lose our higher priority), then the task might get
+ * scheduled away before the wake up can take place.
*/
- if (cmpxchg_futex_value_locked(&oldval, uaddr, uval, 0))
- return -EFAULT;
- if (oldval != uval)
- return -EAGAIN;
+ spin_unlock(&hb->lock);
+ wake_up_q(&wake_q);
+ if (deboost)
+ rt_mutex_adjust_prio(current);
return 0;
}
{
struct futex_hash_bucket *hb;
struct futex_q *this, *next;
- struct plist_head *head;
union futex_key key = FUTEX_KEY_INIT;
int ret;
+ WAKE_Q(wake_q);
if (!bitset)
return -EINVAL;
goto out;
hb = hash_futex(&key);
+
+ /* Make sure we really have tasks to wakeup */
+ if (!hb_waiters_pending(hb))
+ goto out_put_key;
+
spin_lock(&hb->lock);
- head = &hb->chain;
- plist_for_each_entry_safe(this, next, head, list) {
+ plist_for_each_entry_safe(this, next, &hb->chain, list) {
if (match_futex (&this->key, &key)) {
if (this->pi_state || this->rt_waiter) {
ret = -EINVAL;
if (!(this->bitset & bitset))
continue;
- wake_futex(this);
+ mark_wake_futex(&wake_q, this);
if (++ret >= nr_wake)
break;
}
}
spin_unlock(&hb->lock);
+ wake_up_q(&wake_q);
+out_put_key:
put_futex_key(&key);
out:
return ret;
{
union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
struct futex_hash_bucket *hb1, *hb2;
- struct plist_head *head;
struct futex_q *this, *next;
int ret, op_ret;
+ WAKE_Q(wake_q);
retry:
ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, VERIFY_READ);
goto retry;
}
- head = &hb1->chain;
-
- plist_for_each_entry_safe(this, next, head, list) {
+ plist_for_each_entry_safe(this, next, &hb1->chain, list) {
if (match_futex (&this->key, &key1)) {
if (this->pi_state || this->rt_waiter) {
ret = -EINVAL;
goto out_unlock;
}
- wake_futex(this);
+ mark_wake_futex(&wake_q, this);
if (++ret >= nr_wake)
break;
}
}
if (op_ret > 0) {
- head = &hb2->chain;
-
op_ret = 0;
- plist_for_each_entry_safe(this, next, head, list) {
+ plist_for_each_entry_safe(this, next, &hb2->chain, list) {
if (match_futex (&this->key, &key2)) {
if (this->pi_state || this->rt_waiter) {
ret = -EINVAL;
goto out_unlock;
}
- wake_futex(this);
+ mark_wake_futex(&wake_q, this);
if (++op_ret >= nr_wake2)
break;
}
out_unlock:
double_unlock_hb(hb1, hb2);
+ wake_up_q(&wake_q);
out_put_keys:
put_futex_key(&key2);
out_put_key1:
*/
if (likely(&hb1->chain != &hb2->chain)) {
plist_del(&q->list, &hb1->chain);
+ hb_waiters_dec(hb1);
+ hb_waiters_inc(hb2);
plist_add(&q->list, &hb2->chain);
q->lock_ptr = &hb2->lock;
}
*
* Return:
* 0 - failed to acquire the lock atomically;
- * 1 - acquired the lock;
+ * >0 - acquired the lock, return value is vpid of the top_waiter
* <0 - error
*/
static int futex_proxy_trylock_atomic(u32 __user *pifutex,
{
struct futex_q *top_waiter = NULL;
u32 curval;
- int ret;
+ int ret, vpid;
if (get_futex_value_locked(&curval, pifutex))
return -EFAULT;
+ if (unlikely(should_fail_futex(true)))
+ return -EFAULT;
+
/*
* Find the top_waiter and determine if there are additional waiters.
* If the caller intends to requeue more than 1 waiter to pifutex,
* the contended case or if set_waiters is 1. The pi_state is returned
* in ps in contended cases.
*/
+ vpid = task_pid_vnr(top_waiter->task);
ret = futex_lock_pi_atomic(pifutex, hb2, key2, ps, top_waiter->task,
set_waiters);
- if (ret == 1)
+ if (ret == 1) {
requeue_pi_wake_futex(top_waiter, key2, hb2);
-
+ return vpid;
+ }
return ret;
}
int drop_count = 0, task_count = 0, ret;
struct futex_pi_state *pi_state = NULL;
struct futex_hash_bucket *hb1, *hb2;
- struct plist_head *head1;
struct futex_q *this, *next;
- u32 curval2;
+ WAKE_Q(wake_q);
if (requeue_pi) {
+ /*
+ * Requeue PI only works on two distinct uaddrs. This
+ * check is only valid for private futexes. See below.
+ */
+ if (uaddr1 == uaddr2)
+ return -EINVAL;
+
/*
* requeue_pi requires a pi_state, try to allocate it now
* without any locks in case it fails.
}
retry:
- if (pi_state != NULL) {
- /*
- * We will have to lookup the pi_state again, so free this one
- * to keep the accounting correct.
- */
- free_pi_state(pi_state);
- pi_state = NULL;
- }
-
ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, VERIFY_READ);
if (unlikely(ret != 0))
goto out;
if (unlikely(ret != 0))
goto out_put_key1;
+ /*
+ * The check above which compares uaddrs is not sufficient for
+ * shared futexes. We need to compare the keys:
+ */
+ if (requeue_pi && match_futex(&key1, &key2)) {
+ ret = -EINVAL;
+ goto out_put_keys;
+ }
+
hb1 = hash_futex(&key1);
hb2 = hash_futex(&key2);
retry_private:
+ hb_waiters_inc(hb2);
double_lock_hb(hb1, hb2);
if (likely(cmpval != NULL)) {
if (unlikely(ret)) {
double_unlock_hb(hb1, hb2);
+ hb_waiters_dec(hb2);
ret = get_user(curval, uaddr1);
if (ret)
* At this point the top_waiter has either taken uaddr2 or is
* waiting on it. If the former, then the pi_state will not
* exist yet, look it up one more time to ensure we have a
- * reference to it.
+ * reference to it. If the lock was taken, ret contains the
+ * vpid of the top waiter task.
*/
- if (ret == 1) {
+ if (ret > 0) {
WARN_ON(pi_state);
drop_count++;
task_count++;
- ret = get_futex_value_locked(&curval2, uaddr2);
- if (!ret)
- ret = lookup_pi_state(curval2, hb2, &key2,
- &pi_state);
+ /*
+ * If we acquired the lock, then the user
+ * space value of uaddr2 should be vpid. It
+ * cannot be changed by the top waiter as it
+ * is blocked on hb2 lock if it tries to do
+ * so. If something fiddled with it behind our
+ * back the pi state lookup might unearth
+ * it. So we rather use the known value than
+ * rereading and handing potential crap to
+ * lookup_pi_state.
+ */
+ ret = lookup_pi_state(ret, hb2, &key2, &pi_state);
}
switch (ret) {
case 0:
break;
case -EFAULT:
+ free_pi_state(pi_state);
+ pi_state = NULL;
double_unlock_hb(hb1, hb2);
+ hb_waiters_dec(hb2);
put_futex_key(&key2);
put_futex_key(&key1);
ret = fault_in_user_writeable(uaddr2);
goto retry;
goto out;
case -EAGAIN:
- /* The owner was exiting, try again. */
+ /*
+ * Two reasons for this:
+ * - Owner is exiting and we just wait for the
+ * exit to complete.
+ * - The user space value changed.
+ */
+ free_pi_state(pi_state);
+ pi_state = NULL;
double_unlock_hb(hb1, hb2);
+ hb_waiters_dec(hb2);
put_futex_key(&key2);
put_futex_key(&key1);
cond_resched();
}
}
- head1 = &hb1->chain;
- plist_for_each_entry_safe(this, next, head1, list) {
+ plist_for_each_entry_safe(this, next, &hb1->chain, list) {
if (task_count - nr_wake >= nr_requeue)
break;
* woken by futex_unlock_pi().
*/
if (++task_count <= nr_wake && !requeue_pi) {
- wake_futex(this);
+ mark_wake_futex(&wake_q, this);
continue;
}
this->pi_state = pi_state;
ret = rt_mutex_start_proxy_lock(&pi_state->pi_mutex,
this->rt_waiter,
- this->task, 1);
+ this->task);
if (ret == 1) {
/* We got the lock. */
requeue_pi_wake_futex(this, &key2, hb2);
}
out_unlock:
+ free_pi_state(pi_state);
double_unlock_hb(hb1, hb2);
+ wake_up_q(&wake_q);
+ hb_waiters_dec(hb2);
/*
* drop_futex_key_refs() must be called outside the spinlocks. During
out_put_key1:
put_futex_key(&key1);
out:
- if (pi_state != NULL)
- free_pi_state(pi_state);
return ret ? ret : task_count;
}
struct futex_hash_bucket *hb;
hb = hash_futex(&q->key);
+
+ /*
+ * Increment the counter before taking the lock so that
+ * a potential waker won't miss a to-be-slept task that is
+ * waiting for the spinlock. This is safe as all queue_lock()
+ * users end up calling queue_me(). Similarly, for housekeeping,
+ * decrement the counter at queue_unlock() when some error has
+ * occurred and we don't end up adding the task to the list.
+ */
+ hb_waiters_inc(hb);
+
q->lock_ptr = &hb->lock;
- spin_lock(&hb->lock);
+ spin_lock(&hb->lock); /* implies MB (A) */
return hb;
}
static inline void
-queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb)
+queue_unlock(struct futex_hash_bucket *hb)
__releases(&hb->lock)
{
spin_unlock(&hb->lock);
+ hb_waiters_dec(hb);
}
/**
{
/*
* The task state is guaranteed to be set before another task can
- * wake it. set_current_state() is implemented using set_mb() and
+ * wake it. set_current_state() is implemented using smp_store_mb() and
* queue_me() calls spin_unlock() upon completion, both serializing
* access to the hash list and forcing another memory barrier.
*/
queue_me(q, hb);
/* Arm the timer */
- if (timeout) {
+ if (timeout)
hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS);
- if (!hrtimer_active(&timeout->timer))
- timeout->task = NULL;
- }
/*
* If we have been removed from the hash list, then another task
* is no timeout, or if it has yet to expire.
*/
if (!timeout || timeout->task)
- schedule();
+ freezable_schedule();
}
__set_current_state(TASK_RUNNING);
}
ret = get_futex_value_locked(&uval, uaddr);
if (ret) {
- queue_unlock(q, *hb);
+ queue_unlock(*hb);
ret = get_user(uval, uaddr);
if (ret)
}
if (uval != val) {
- queue_unlock(q, *hb);
+ queue_unlock(*hb);
ret = -EWOULDBLOCK;
}
if (!abs_time)
goto out;
- restart = ¤t_thread_info()->restart_block;
+ restart = ¤t->restart_block;
restart->fn = futex_wait_restart;
restart->futex.uaddr = uaddr;
restart->futex.val = val;
/*
* 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.)
+ * if there are waiters then it will block as a consequence of relying
+ * on rt-mutexes, it does PI, etc. (Due to races the kernel might see
+ * a 0 value of the futex too.).
+ *
+ * Also serves as futex trylock_pi()'ing, and due semantics.
*/
-static int futex_lock_pi(u32 __user *uaddr, unsigned int flags, int detect,
+static int futex_lock_pi(u32 __user *uaddr, unsigned int flags,
ktime_t *time, int trylock)
{
struct hrtimer_sleeper timeout, *to = NULL;
ret = futex_lock_pi_atomic(uaddr, hb, &q.key, &q.pi_state, current, 0);
if (unlikely(ret)) {
+ /*
+ * Atomic work succeeded and we got the lock,
+ * or failed. Either way, we do _not_ block.
+ */
switch (ret) {
case 1:
/* We got the lock. */
goto uaddr_faulted;
case -EAGAIN:
/*
- * Task is exiting and we just wait for the
- * exit to complete.
+ * Two reasons for this:
+ * - Task is exiting and we just wait for the
+ * exit to complete.
+ * - The user space value changed.
*/
- queue_unlock(&q, hb);
+ queue_unlock(hb);
put_futex_key(&q.key);
cond_resched();
goto retry;
/*
* Block on the PI mutex:
*/
- if (!trylock)
- ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1);
- else {
+ if (!trylock) {
+ ret = rt_mutex_timed_futex_lock(&q.pi_state->pi_mutex, to);
+ } else {
ret = rt_mutex_trylock(&q.pi_state->pi_mutex);
/* Fixup the trylock return value: */
ret = ret ? 0 : -EWOULDBLOCK;
goto out_put_key;
out_unlock_put_key:
- queue_unlock(&q, hb);
+ queue_unlock(hb);
out_put_key:
put_futex_key(&q.key);
return ret != -EINTR ? ret : -ERESTARTNOINTR;
uaddr_faulted:
- queue_unlock(&q, hb);
+ queue_unlock(hb);
ret = fault_in_user_writeable(uaddr);
if (ret)
*/
static int futex_unlock_pi(u32 __user *uaddr, unsigned int flags)
{
- struct futex_hash_bucket *hb;
- struct futex_q *this, *next;
- struct plist_head *head;
+ u32 uninitialized_var(curval), uval, vpid = task_pid_vnr(current);
union futex_key key = FUTEX_KEY_INIT;
- u32 uval, vpid = task_pid_vnr(current);
+ struct futex_hash_bucket *hb;
+ struct futex_q *match;
int ret;
retry:
return -EPERM;
ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, VERIFY_WRITE);
- if (unlikely(ret != 0))
- goto out;
+ if (ret)
+ return ret;
hb = hash_futex(&key);
spin_lock(&hb->lock);
/*
- * To avoid races, try to do the TID -> 0 atomic transition
- * again. If it succeeds then we can return without waking
- * anyone else up:
- */
- if (!(uval & FUTEX_OWNER_DIED) &&
- cmpxchg_futex_value_locked(&uval, uaddr, vpid, 0))
- goto pi_faulted;
- /*
- * Rare case: we managed to release the lock atomically,
- * no need to wake anyone else up:
- */
- if (unlikely(uval == vpid))
- goto out_unlock;
-
- /*
- * Ok, other tasks may need to be woken up - check waiters
- * and do the wakeup if necessary:
+ * Check waiters first. We do not trust user space values at
+ * all and we at least want to know if user space fiddled
+ * with the futex value instead of blindly unlocking.
*/
- head = &hb->chain;
-
- plist_for_each_entry_safe(this, next, head, list) {
- if (!match_futex (&this->key, &key))
- continue;
- ret = wake_futex_pi(uaddr, uval, this);
+ match = futex_top_waiter(hb, &key);
+ if (match) {
+ ret = wake_futex_pi(uaddr, uval, match, hb);
/*
- * The atomic access to the futex value
- * generated a pagefault, so retry the
- * user-access and the wakeup:
+ * In case of success wake_futex_pi dropped the hash
+ * bucket lock.
+ */
+ if (!ret)
+ goto out_putkey;
+ /*
+ * The atomic access to the futex value generated a
+ * pagefault, so retry the user-access and the wakeup:
*/
if (ret == -EFAULT)
goto pi_faulted;
+ /*
+ * A unconditional UNLOCK_PI op raced against a waiter
+ * setting the FUTEX_WAITERS bit. Try again.
+ */
+ if (ret == -EAGAIN) {
+ spin_unlock(&hb->lock);
+ put_futex_key(&key);
+ goto retry;
+ }
+ /*
+ * wake_futex_pi has detected invalid state. Tell user
+ * space.
+ */
goto out_unlock;
}
+
/*
- * No waiters - kernel unlocks the futex:
+ * We have no kernel internal state, i.e. no waiters in the
+ * kernel. Waiters which are about to queue themselves are stuck
+ * on hb->lock. So we can safely ignore them. We do neither
+ * preserve the WAITERS bit not the OWNER_DIED one. We are the
+ * owner.
*/
- if (!(uval & FUTEX_OWNER_DIED)) {
- ret = unlock_futex_pi(uaddr, uval);
- if (ret == -EFAULT)
- goto pi_faulted;
- }
+ if (cmpxchg_futex_value_locked(&curval, uaddr, uval, 0))
+ goto pi_faulted;
+
+ /*
+ * If uval has changed, let user space handle it.
+ */
+ ret = (curval == uval) ? 0 : -EAGAIN;
out_unlock:
spin_unlock(&hb->lock);
+out_putkey:
put_futex_key(&key);
-
-out:
return ret;
pi_faulted:
* Unqueue the futex_q and determine which it was.
*/
plist_del(&q->list, &hb->chain);
+ hb_waiters_dec(hb);
/* Handle spurious wakeups gracefully */
ret = -EWOULDBLOCK;
* futex_wait_requeue_pi() - Wait on uaddr and take uaddr2
* @uaddr: the futex we initially wait on (non-pi)
* @flags: futex flags (FLAGS_SHARED, FLAGS_CLOCKRT, etc.), they must be
- * the same type, no requeueing from private to shared, etc.
+ * the same type, no requeueing from private to shared, etc.
* @val: the expected value of uaddr
* @abs_time: absolute timeout
* @bitset: 32 bit wakeup bitset set by userspace, defaults to all
* code while we sleep on uaddr.
*/
debug_rt_mutex_init_waiter(&rt_waiter);
+ RB_CLEAR_NODE(&rt_waiter.pi_tree_entry);
+ RB_CLEAR_NODE(&rt_waiter.tree_entry);
rt_waiter.task = NULL;
ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, VERIFY_WRITE);
if (ret)
goto out_key2;
+ /*
+ * The check above which compares uaddrs is not sufficient for
+ * shared futexes. We need to compare the keys:
+ */
+ if (match_futex(&q.key, &key2)) {
+ queue_unlock(hb);
+ ret = -EINVAL;
+ goto out_put_keys;
+ }
+
/* Queue the futex_q, drop the hb lock, wait for wakeup. */
futex_wait_queue_me(hb, &q, to);
if (q.pi_state && (q.pi_state->owner != current)) {
spin_lock(q.lock_ptr);
ret = fixup_pi_state_owner(uaddr2, &q, current);
+ /*
+ * Drop the reference to the pi state which
+ * the requeue_pi() code acquired for us.
+ */
+ free_pi_state(q.pi_state);
spin_unlock(q.lock_ptr);
}
} else {
*/
WARN_ON(!q.pi_state);
pi_mutex = &q.pi_state->pi_mutex;
- ret = rt_mutex_finish_proxy_lock(pi_mutex, to, &rt_waiter, 1);
+ ret = rt_mutex_finish_proxy_lock(pi_mutex, to, &rt_waiter);
debug_rt_mutex_free_waiter(&rt_waiter);
spin_lock(q.lock_ptr);
}
ret = -EPERM;
- if (!ptrace_may_access(p, PTRACE_MODE_READ))
+ if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS))
goto err_unlock;
head = p->robust_list;
case FUTEX_WAKE_OP:
return futex_wake_op(uaddr, flags, uaddr2, val, val2, val3);
case FUTEX_LOCK_PI:
- return futex_lock_pi(uaddr, flags, val, timeout, 0);
+ return futex_lock_pi(uaddr, flags, timeout, 0);
case FUTEX_UNLOCK_PI:
return futex_unlock_pi(uaddr, flags);
case FUTEX_TRYLOCK_PI:
- return futex_lock_pi(uaddr, flags, 0, timeout, 1);
+ return futex_lock_pi(uaddr, flags, NULL, 1);
case FUTEX_WAIT_REQUEUE_PI:
val3 = FUTEX_BITSET_MATCH_ANY;
return futex_wait_requeue_pi(uaddr, flags, val, timeout, val3,
if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
cmd == FUTEX_WAIT_BITSET ||
cmd == FUTEX_WAIT_REQUEUE_PI)) {
+ if (unlikely(should_fail_futex(!(op & FUTEX_PRIVATE_FLAG))))
+ return -EFAULT;
if (copy_from_user(&ts, utime, sizeof(ts)) != 0)
return -EFAULT;
if (!timespec_valid(&ts))
return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
}
-static int __init futex_init(void)
+static void __init futex_detect_cmpxchg(void)
{
+#ifndef CONFIG_HAVE_FUTEX_CMPXCHG
u32 curval;
- int i;
/*
* This will fail and we want it. Some arch implementations do
*/
if (cmpxchg_futex_value_locked(&curval, NULL, 0, 0) == -EFAULT)
futex_cmpxchg_enabled = 1;
+#endif
+}
+
+static int __init futex_init(void)
+{
+ unsigned int futex_shift;
+ unsigned long i;
+
+#if CONFIG_BASE_SMALL
+ futex_hashsize = 16;
+#else
+ futex_hashsize = roundup_pow_of_two(256 * num_possible_cpus());
+#endif
+
+ futex_queues = alloc_large_system_hash("futex", sizeof(*futex_queues),
+ futex_hashsize, 0,
+ futex_hashsize < 256 ? HASH_SMALL : 0,
+ &futex_shift, NULL,
+ futex_hashsize, futex_hashsize);
+ futex_hashsize = 1UL << futex_shift;
+
+ futex_detect_cmpxchg();
- for (i = 0; i < ARRAY_SIZE(futex_queues); i++) {
+ for (i = 0; i < futex_hashsize; i++) {
+ atomic_set(&futex_queues[i].waiters, 0);
plist_head_init(&futex_queues[i].chain);
spin_lock_init(&futex_queues[i].lock);
}
projects / firefly-linux-kernel-4.4.55.git / blobdiff