From: Jens Axboe <axboe@kernel.dk>
To: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@kernel.org>
Cc: tglx@linutronix.de, 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,
Geert Uytterhoeven <geert@linux-m68k.org>
Subject: Re: [PATCH v3 10/15] futex: Add sys_futex_requeue()
Date: Fri, 22 Sep 2023 07:56:28 -0600 [thread overview]
Message-ID: <ec7cf6ad-3081-47a8-be83-af6eb7befa35@kernel.dk> (raw)
In-Reply-To: <20230922110335.GC7080@noisy.programming.kicks-ass.net>
On 9/22/23 5:03 AM, Peter Zijlstra wrote:
> On Fri, Sep 22, 2023 at 11:35:03AM +0200, Ingo Molnar wrote:
>>
>> * peterz@infradead.org <peterz@infradead.org> wrote:
>>
>>> --- linux-2.6.orig/kernel/futex/syscalls.c
>>> +++ linux-2.6/kernel/futex/syscalls.c
>>> @@ -396,6 +396,44 @@ SYSCALL_DEFINE6(futex_wait,
>>> return ret;
>>> }
>>>
>>> +/*
>>> + * 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;
>>> + int ret;
>>> +
>>> + if (flags)
>>> + return -EINVAL;
>>
>> Small detail, but isn't -ENOSYS the canonical error code for functionality
>> not yet implemented - which the unused 'flags' ABI is arguably?
>>
>> -EINVAL is for recognized but incorrect parameters, such as:
>
> IIUC 'unknown flag' falls into the -EINVAL return category. Here we
> happen to have no known flags, but that should not matter.
Yep, -ENOSYS is for not having the syscall at all, -EINVAL for unknown
flags set.
--
Jens Axboe
next prev parent reply other threads:[~2023-09-22 13:56 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-21 10:45 [PATCH v3 00/15] futex: More futex2 bits peterz
2023-09-21 10:45 ` [PATCH v3 04/15] futex: Validate futex value against futex size peterz
2023-09-21 10:45 ` [PATCH v3 05/15] futex: Add sys_futex_wake() peterz
2023-09-21 10:45 ` [PATCH v3 07/15] futex: Add sys_futex_wait() peterz
2023-09-21 10:45 ` [PATCH v3 08/15] futex: Propagate flags into get_futex_key() peterz
2023-09-21 10:45 ` [PATCH v3 09/15] futex: Add flags2 argument to futex_requeue() peterz
2023-09-21 10:45 ` [PATCH v3 10/15] futex: Add sys_futex_requeue() peterz
2023-09-22 9:35 ` Ingo Molnar
2023-09-22 11:03 ` Peter Zijlstra
2023-09-22 13:56 ` Jens Axboe [this message]
2023-09-21 10:45 ` [PATCH v3 11/15] mm: Add vmalloc_huge_node() peterz
2023-09-21 10:45 ` [PATCH v3 12/15] futex: Implement FUTEX2_NUMA peterz
2023-09-21 10:45 ` [PATCH v3 13/15] futex: Propagate flags into futex_get_value_locked() peterz
2023-09-21 10:45 ` [PATCH v3 14/15] futex: Enable FUTEX2_{8,16} peterz
2023-09-21 10:45 ` [PATCH v3 15/15] futex,selftests: Extend the futex selftests peterz
2023-09-21 11:41 ` Peter Zijlstra
[not found] ` <20230921105248.048643656@noisy.programming.kicks-ass.net>
2023-09-21 15:14 ` [PATCH v3 06/15] futex: FLAGS_STRICT Thomas Gleixner
2023-09-22 20:01 ` futex2 numa stuff Peter Zijlstra
2023-09-22 20:01 ` [PATCH 15/15] futex,selftests: Extend the futex selftests Peter Zijlstra
2023-09-22 20:01 ` [PATCH 16/15] futex,selftests: Extend the futex selftests for NUMA Peter Zijlstra
2023-09-22 20:01 ` [PATCH 17/15] [HACK] futex: Force futex hash collision Peter Zijlstra
2023-09-28 13:40 ` futex2 numa stuff Davidlohr Bueso
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