Re: [PATCH 1/4] futex: Prepare for futex_wait_multiple()

[Thomas Gleixner via Libc-alpha <libc-alpha@sourceware.org>]

Andre,

On Thu, Aug 05 2021 at 16:04, André Almeida wrote:
> +/*
> + * Futex flags used to encode options to functions and preserve them across
> + * restarts.
> + */
> +#ifdef CONFIG_MMU
> +# define FLAGS_SHARED		0x01
> +#else
> +/*
> + * NOMMU does not have per process address space. Let the compiler optimize
> + * code away.
> + */
> +# define FLAGS_SHARED		0x00
> +#endif
> +#define FLAGS_CLOCKRT		0x02
> +#define FLAGS_HAS_TIMEOUT	0x04
> +
>  /*
>   * Futexes are matched on equal values of this key.
>   * The key type depends on whether it's a shared or private mapping.
> @@ -50,8 +66,52 @@ union futex_key {
>  	} both;
>  };
>  
> +/**
> + * struct futex_q - The hashed futex queue entry, one per waiting task
> + * @list:		priority-sorted list of tasks waiting on this futex
> + * @task:		the task waiting on the futex
> + * @lock_ptr:		the hash bucket lock
> + * @key:		the key the futex is hashed on
> + * @pi_state:		optional priority inheritance state
> + * @rt_waiter:		rt_waiter storage for use with requeue_pi
> + * @requeue_pi_key:	the requeue_pi target futex key
> + * @bitset:		bitset for the optional bitmasked wakeup
> + *
> + * We use this hashed waitqueue, instead of a normal wait_queue_entry_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().
> + */
> +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;
> +} __randomize_layout;
> +
>  #define FUTEX_KEY_INIT (union futex_key) { .both = { .ptr = 0ULL } }
>  
> +static const struct futex_q futex_q_init = {
> +	/* list gets initialized in queue_me()*/
> +	.key = FUTEX_KEY_INIT,
> +	.bitset = FUTEX_BITSET_MATCH_ANY
> +};
> +
> +inline struct hrtimer_sleeper *
> +futex_setup_timer(ktime_t *time, struct hrtimer_sleeper *timeout,
> +		  int flags, u64 range_ns);
> +

None of these things belong into the global header. Please move them to
kernel/futex.h.

Thanks,

        tglx