linux-kernel - Re: [PATCH v12 03/21] futex: Move futex_queue() into futex_wait

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Message-ID: <20250516125336.zd1aBkwv@linutronix.de>
Date: Fri, 16 May 2025 14:53:36 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: André Almeida <andrealmeid@...lia.com>
Cc: Darren Hart <dvhart@...radead.org>, linux-kernel@...r.kernel.org,
	Davidlohr Bueso <dave@...olabs.net>, Ingo Molnar <mingo@...hat.com>,
	Juri Lelli <juri.lelli@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Valentin Schneider <vschneid@...hat.com>,
	Waiman Long <longman@...hat.com>
Subject: Re: [PATCH v12 03/21] futex: Move futex_queue() into
 futex_wait_setup()

On 2025-05-05 18:43:16 [-0300], André Almeida wrote:
> > --- a/kernel/futex/waitwake.c
> > +++ b/kernel/futex/waitwake.c
> > @@ -339,18 +339,8 @@ static long futex_wait_restart(struct restart_block *restart);
> >    * @q:		the futex_q to queue up on
> >    * @timeout:	the prepared hrtimer_sleeper, or null for no timeout
> >    */
> > -void futex_wait_queue(struct futex_hash_bucket *hb, struct futex_q *q,
> > -			    struct hrtimer_sleeper *timeout)
> > +void futex_do_wait(struct futex_q *q, struct hrtimer_sleeper *timeout)
> 
> Update the name in the kernel doc comment as well. Also drop from the
> comment the part that says "futex_queue() and ..."

This has been done.

…
> > @@ -636,10 +629,25 @@ int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags,
> >   	}
> >   	if (uval != val) {
> > -		futex_q_unlock(*hb);
> > -		ret = -EWOULDBLOCK;
> > +		futex_q_unlock(hb);
> > +		return -EWOULDBLOCK;
> >   	}
> > +	if (key2 && futex_match(&q->key, key2)) {
> > +		futex_q_unlock(hb);
> > +		return -EINVAL;
> 
> Please add this new ret value in the kernel doc too.

I'm going to add this:

--- a/kernel/futex/waitwake.c
+++ b/kernel/futex/waitwake.c
@@ -585,7 +585,8 @@ int futex_wait_multiple(struct futex_vector *vs, unsigned int count,
  *
  * Return:
  *  -  0 - uaddr contains val and hb has been locked;
- *  - <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlocked
+ *  - <0 - On error and the hb is unlocked. A possible reason: the uaddr can not
+ *	   be read, does not contain the expected value or is not properly aligned.
  */
 int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags,
 		     struct futex_q *q, union futex_key *key2,

Sebastian