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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Peter Zijlstra <peterz@infradead.org>
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  v2 11/14] futex: Implement FUTEX2_NUMA
In-Reply-To: <20230808085406.GU212435@hirez.programming.kicks-ass.net>
References: <20230807121843.710612856@infradead.org>
 <20230807123323.504975124@infradead.org> <87fs4utv6f.ffs@tglx>
 <20230808085406.GU212435@hirez.programming.kicks-ass.net>
Date:   Tue, 08 Aug 2023 11:12:09 +0200
Message-ID: <87y1ilsxsm.ffs@tglx>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

On Tue, Aug 08 2023 at 10:54, Peter Zijlstra wrote:
> On Mon, Aug 07, 2023 at 11:11:04PM +0200, Thomas Gleixner wrote:
>> On Mon, Aug 07 2023 at 14:18, Peter Zijlstra wrote:
>> >  /**
>> >   * futex_hash - Return the hash bucket in the global hash
>> >   * @key:	Pointer to the futex key for which the hash is calculated
>> > @@ -114,10 +137,29 @@ late_initcall(fail_futex_debugfs);
>> >   */
>> >  struct futex_hash_bucket *futex_hash(union futex_key *key)
>> >  {
>> > -	u32 hash = jhash2((u32 *)key, offsetof(typeof(*key), both.offset) / 4,
>> > +	u32 hash = jhash2((u32 *)key,
>> > +			  offsetof(typeof(*key), both.offset) / sizeof(u32),
>> >  			  key->both.offset);
>> > +	int node = key->both.node;
>> > +
>> > +	if (node == -1) {
>> 
>> NUMA_NO_NODE please all over the place.
>
> Ah, so our (futex2) ABI states this needs to be -1, but in theory
> someone could come along and change the kernel internal NUMA_NO_NODE to
> something else.
>
> That is, I explicitly chose not to use it. I can of course, because as
> of now these values do match.

Fair enough, but can we at least have a proper define in the futex2 ABI
please?