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SubjectRe: [PATCH] futex: Fix a faulty comment.
Hi André.

That patch was definitely wrong, I apologize.

However, since futex_wait_multiple_setup() sets the last index of
futex that was woken up,
shouldn't the comment be modified as below?

If so, I will resend a patch.

/*
- * Even if something went wrong, if we find out that a futex
- * was woken, we don't return error and return this index to
- * userspace
+ * Even if something went wrong, if we find out that any futex
+ * was woken, we don't return error and return the last index
+ * awoken to userspace
*/
*woken = unqueue_multiple(vs, i);
if (*woken >= 0)

I sent the patch because I thought this was important enough to be corrected.

Let me know If this is not crucial enough to be patched, so I won't
keep sending comment-fixing patches.

Thank you.
Jangwoong Kim.

2021년 12월 6일 (월) 오후 9:12, André Almeida <andrealmeid@collabora.com>님이 작성:
>
> Hi Jangwoong,
>
> Thanks for your patch! However...
>
> Às 15:14 de 04/12/21, 6812skiii@gmail.com escreveu:
> > From: Jangwoong Kim <6812skiii@gmail.com>
> >
> > We return 1, not the index of futex woken up.
> >
> > Signed-off-by: Jangwoong Kim <6812skiii@gmail.com>
> > ---
> > kernel/futex/waitwake.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/futex/waitwake.c b/kernel/futex/waitwake.c
> > index 4ce0923f1ce3..d148e5d4956b 100644
> > --- a/kernel/futex/waitwake.c
> > +++ b/kernel/futex/waitwake.c
> > @@ -455,8 +455,8 @@ static int futex_wait_multiple_setup(struct futex_vector *vs, int count, int *wo
> >
> > /*
> > * Even if something went wrong, if we find out that a futex
> > - * was woken, we don't return error and return this index to
> > - * userspace
> > + * was woken, we don't return error and make userspace aware
> > + * of this by returning 1.
>
> We return to userspace the value at *woken, so your fix is wrong. Have a
> look at futex_wait_multiple():
>
> ret = futex_wait_multiple_setup(vs, count, &hint);
> if (ret) {
> if (ret > 0) {
> /* A futex was woken during setup */
> ret = hint;
> }
> return ret;
> }
>
> When we return 1 at futex_wait_multiple_setup(), we end up returning the
> hint/woken value to userspace.
>
> Let me know if you have questions.
>
> André

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