NAME¶

struct_futex_q - The hashed futex queue entry, one per waiting task

SYNOPSIS¶

struct futex_q {


  struct plist_node list;


  struct task_struct * task;


  spinlock_t * lock_ptr;


  union futex_key key;


  struct futex_pi_state * pi_state;


  struct rt_mutex_waiter * rt_waiter;


  union futex_key * requeue_pi_key;


  u32 bitset;
};  

MEMBERS¶

struct plist_node list

struct task_struct * task

spinlock_t * lock_ptr

union futex_key key

struct futex_pi_state * pi_state

struct rt_mutex_waiter * rt_waiter

union futex_key * requeue_pi_key

u32 bitset

DESCRIPTION¶

We use this hashed waitqueue, instead of a normal wait_queue_t, so we can wake only the relevant ones (hashed queues may be shared).

A futex_q has a woken state, just like tasks have TASK_RUNNING. It is considered woken when plist_node_empty(q->list) || q->lock_ptr == 0. The order of wakeup is always to make the first condition true, then the second.

PI futexes are typically woken before they are removed from the hash list via the rt_mutex code. See unqueue_me_pi.

AUTHOR¶

Rusty Russell <rusty@rustcorp.com.au>

COPYRIGHT¶