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Date:   Mon, 31 Jul 2023 19:38:56 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     axboe@kernel.dk, linux-kernel@vger.kernel.org, mingo@redhat.com,
        dvhart@infradead.org, dave@stgolabs.net, andrealmeid@igalia.com,
        Andrew Morton <akpm@linux-foundation.org>, urezki@gmail.com,
        hch@infradead.org, lstoakes@gmail.com,
        Arnd Bergmann <arnd@arndb.de>, linux-api@vger.kernel.org,
        linux-mm@kvack.org, linux-arch@vger.kernel.org,
        malteskarupke@web.de
Subject: Re: [PATCH v1 09/14] futex: Add sys_futex_requeue()
Message-ID: <20230731173856.GQ29590@hirez.programming.kicks-ass.net>
References: <20230721102237.268073801@infradead.org>
 <20230721105744.298661259@infradead.org>
 <87sf94m222.ffs@tglx>
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On Mon, Jul 31, 2023 at 07:19:17PM +0200, Thomas Gleixner wrote:
> On Fri, Jul 21 2023 at 12:22, Peter Zijlstra wrote:
> > +/*
> > + * sys_futex_requeue - Requeue a waiter from one futex to another
> > + * @waiters:	array describing the source and destination futex
> > + * @flags:	unused
> > + * @nr_wake:	number of futexes to wake
> > + * @nr_requeue:	number of futexes to requeue
> > + *
> > + * Identical to the traditional FUTEX_CMP_REQUEUE op, except it is part of the
> > + * futex2 family of calls.
> > + */
> > +
> > +SYSCALL_DEFINE4(futex_requeue,
> > +		struct futex_waitv __user *, waiters,
> > +		unsigned int, flags,
> > +		int, nr_wake,
> > +		int, nr_requeue)
> > +{
> > +	struct futex_vector futexes[2];
> > +	u32 cmpval;
> 
> So this is explictely u32. I'm completely confused vs. the 64 bit futex
> size variant enablement earlier in the series by now.

As per the previous email; these patches only enable the syscall part of
64bit futexes, they do not convert the core, and per futex_flags_valid()
(patches 4 and 13), explicitly disallow having FUTEX2_64 set.


-       /* Only 32bit futexes are implemented -- for now */
-       if ((flags & FLAGS_SIZE_MASK) != FLAGS_SIZE_32)
+       /* 64bit futexes aren't implemented -- yet */
+       if ((flags & FLAGS_SIZE_MASK) == FLAGS_SIZE_64)
		return false;