[5/7] futex: make futex_parse_waitv() available as a helper
Commit Message
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(-)
Comments
On Tue, Jul 11, 2023 at 06:47:03PM -0600, Jens Axboe wrote:
> 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.
> 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;
> }
I'm not following; I even applied all your patches up to this point, but
futex_queue() still reads:
static inline void futex_queue(struct futex_q *q, struct futex_hash_bucket *hb)
__releases(&hb->lock)
{
__futex_queue(q, hb);
spin_unlock(&hb->lock);
}
How would it be different and overwrite anything ?!?
On 7/12/23 3:25?AM, Peter Zijlstra wrote:
> On Tue, Jul 11, 2023 at 06:47:03PM -0600, Jens Axboe wrote:
>
>> 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.
>
>> 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;
>> }
>
> I'm not following; I even applied all your patches up to this point, but
> futex_queue() still reads:
>
> static inline void futex_queue(struct futex_q *q, struct futex_hash_bucket *hb)
> __releases(&hb->lock)
> {
> __futex_queue(q, hb);
> spin_unlock(&hb->lock);
> }
>
> How would it be different and overwrite anything ?!?
Good catch, this is a leftover from storing the task/wakeup data
separately. But I got rid of that, so it's stale comment at this point
and we can certainly use futex_queue() here again and drop this hunk.
Will make that edit.
@@ -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);
@@ -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);
@@ -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;
}