[PATCH 5/7] futex: make futex_parse_waitv() available as a helper

Jens Axboe
2023-07-12T00:47:32Z

To make it more generically useful, augment it with allowing the caller
to pass in the wake handler and wake data. Convert the futex_waitv()
syscall, passing in the default handlers.

Since we now provide a way to pass in a wake handler and data, ensure we
use __futex_queue() to avoid having futex_queue() overwrite our wait
data.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
kernel/futex/futex.h | 5 +++++
kernel/futex/syscalls.c | 14 ++++++++++----
kernel/futex/waitwake.c | 3 ++-
3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/kernel/futex/futex.h b/kernel/futex/futex.h
index 75dec2ec7469..ed5a7ccd2e99 100644
--- a/kernel/futex/futex.h
+++ b/kernel/futex/futex.h
@@ -284,6 +284,11 @@ struct futex_vector {
struct futex_q q;
};

+extern int futex_parse_waitv(struct futex_vector *futexv,
+ struct futex_waitv __user *uwaitv,
+ unsigned int nr_futexes, futex_wake_fn *wake,
+ void *wake_data);
+
extern int futex_wait_multiple(struct futex_vector *vs, unsigned int count,
struct hrtimer_sleeper *to);

diff --git a/kernel/futex/syscalls.c b/kernel/futex/syscalls.c
index 75ca8c41cc94..8ac70bfb89fc 100644
--- a/kernel/futex/syscalls.c
+++ b/kernel/futex/syscalls.c
@@ -184,12 +184,15 @@ SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
* @futexv: Kernel side list of waiters to be filled
* @uwaitv: Userspace list to be parsed
* @nr_futexes: Length of futexv
+ * @wake: Wake to call when futex is woken
+ * @wake_data: Data for the wake handler
*
* Return: Error code on failure, 0 on success
*/
-static int futex_parse_waitv(struct futex_vector *futexv,
- struct futex_waitv __user *uwaitv,
- unsigned int nr_futexes)
+int futex_parse_waitv(struct futex_vector *futexv,
+ struct futex_waitv __user *uwaitv,
+ unsigned int nr_futexes, futex_wake_fn *wake,
+ void *wake_data)
{
struct futex_waitv aux;
unsigned int i;
@@ -208,6 +211,8 @@ static int futex_parse_waitv(struct futex_vector *futexv,
futexv[i].w.val = aux.val;
futexv[i].w.uaddr = aux.uaddr;
futexv[i].q = futex_q_init;
+ futexv[i].q.wake = wake;
+ futexv[i].q.wake_data = wake_data;
}

return 0;
@@ -284,7 +289,8 @@ SYSCALL_DEFINE5(futex_waitv, struct futex_waitv __user *, waiters,
goto destroy_timer;
}

- ret = futex_parse_waitv(futexv, waiters, nr_futexes);
+ ret = futex_parse_waitv(futexv, waiters, nr_futexes, futex_wake_mark,
+ NULL);
if (!ret)
ret = futex_wait_multiple(futexv, nr_futexes, timeout ? &to : NULL);

diff --git a/kernel/futex/waitwake.c b/kernel/futex/waitwake.c
index 3471af87cb7d..dfd02ca5ecfa 100644
--- a/kernel/futex/waitwake.c
+++ b/kernel/futex/waitwake.c
@@ -446,7 +446,8 @@ static int futex_wait_multiple_setup(struct futex_vector *vs, int count, int *wo
* next futex. Queue each futex at this moment so hb can
* be unlocked.
*/
- futex_queue(q, hb);
+ __futex_queue(q, hb);
+ spin_unlock(&hb->lock);
continue;
}

--
2.40.1