From: Jangwoong Kim <6812skiii@gmail.com>
To: "André Almeida" <andrealmeid@collabora.com>
Cc: peterz@infradead.org, mingo@redhat.com, tglx@linutronix.de,
dvhart@infradead.org, dave@stgolabs.net,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] futex: Fix a faulty comment.
Date: Tue, 7 Dec 2021 02:44:36 +0900 [thread overview]
Message-ID: <CAF=mnpi65WtnK_mF1f8GfMEczS1ruj8q4YbA18R5KvWcpkxLxw@mail.gmail.com> (raw)
In-Reply-To: <f7d9194b-6681-48f0-b5e9-11f43d2849bd@collabora.com>
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
next prev parent reply other threads:[~2021-12-06 17:44 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-04 18:14 [PATCH] futex: Fix a faulty comment 6812skiii
2021-12-06 12:12 ` André Almeida
2021-12-06 17:44 ` Jangwoong Kim [this message]
2021-12-06 20:34 ` André Almeida
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