futex: factor out the futex wake handling

In preparation for having another waker that isn't futex_wake_mark(),
add a wake handler in futex_q. No extra data is associated with the
handler outside of struct futex_q itself. futex_wake_mark() is defined as
the standard wakeup helper, now set through futex_q_init like other
defaults.

Normal sync futex waiting relies on wake_q holding tasks that should
be woken up. This is what futex_wake_mark() does, it'll unqueue the
futex and add the associated task to the wake queue. For async usage of
futex waiting, rather than having tasks sleeping on the futex, we'll
need to deal with a futex wake differently. For the planned io_uring
case, that means posting a completion event for the task in question.
Having a definable wake handler can help support that use case.

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/kernel/futex/futex.h b/kernel/futex/futex.h
index a173a9d501e104d471972222c48280620573cb17..547f509b2c87670fd84843ec87a64ffd7953d970 100644 (file)
--- a/kernel/futex/futex.h
+++ b/kernel/futex/futex.h
@@ -139,11 +139,15 @@ struct futex_pi_state {
        union futex_key key;
 } __randomize_layout;
 
+struct futex_q;
+typedef void (futex_wake_fn)(struct wake_q_head *wake_q, struct futex_q *q);
+
 /**
  * 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
+ * @wake:              the wake handler for this queue
  * @key:               the key the futex is hashed on
  * @pi_state:          optional priority inheritance state
  * @rt_waiter:         rt_waiter storage for use with requeue_pi
@@ -168,6 +172,7 @@ struct futex_q {
 
        struct task_struct *task;
        spinlock_t *lock_ptr;
+       futex_wake_fn *wake;
        union futex_key key;
        struct futex_pi_state *pi_state;
        struct rt_mutex_waiter *rt_waiter;

diff --git a/kernel/futex/requeue.c b/kernel/futex/requeue.c
index a0a79954f506a9718ce8c89d3470c868f053bb0f..9dc789399a1a1d0693c005f196a5466a3f00d2a7 100644 (file)
--- a/kernel/futex/requeue.c
+++ b/kernel/futex/requeue.c
@@ -58,6 +58,7 @@ enum {
 
 const struct futex_q futex_q_init = {
        /* list gets initialized in futex_queue()*/
+       .wake           = futex_wake_mark,
        .key            = FUTEX_KEY_INIT,
        .bitset         = FUTEX_BITSET_MATCH_ANY,
        .requeue_state  = ATOMIC_INIT(Q_REQUEUE_PI_NONE),
@@ -593,7 +594,7 @@ retry_private:
                /* Plain futexes just wake or requeue and are done */
                if (!requeue_pi) {
                        if (++task_count <= nr_wake)
-                               futex_wake_mark(&wake_q, this);
+                               this->wake(&wake_q, this);
                        else
                                requeue_futex(this, hb1, hb2, &key2);
                        continue;

diff --git a/kernel/futex/waitwake.c b/kernel/futex/waitwake.c
index 37860f794bf749ecf1381e0efa9fd1db32e41c38..35c6a637a4bb61bb55f86fd6c196680732fc3e4b 100644 (file)
--- a/kernel/futex/waitwake.c
+++ b/kernel/futex/waitwake.c
@@ -177,7 +177,7 @@ int futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset)
                        if (!(this->bitset & bitset))
                                continue;
 
-                       futex_wake_mark(&wake_q, this);
+                       this->wake(&wake_q, this);
                        if (++ret >= nr_wake)
                                break;
                }
@@ -292,7 +292,7 @@ retry_private:
                                ret = -EINVAL;
                                goto out_unlock;
                        }
-                       futex_wake_mark(&wake_q, this);
+                       this->wake(&wake_q, this);
                        if (++ret >= nr_wake)
                                break;
                }
@@ -306,7 +306,7 @@ retry_private:
                                        ret = -EINVAL;
                                        goto out_unlock;
                                }
-                               futex_wake_mark(&wake_q, this);
+                               this->wake(&wake_q, this);
                                if (++op_ret >= nr_wake2)
                                        break;
                        }