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Received: from [177.45.63.19] (helo=[192.168.1.111]) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_128_GCM:128) (Exim) id 1qTA0t-00F9EE-2b; Tue, 08 Aug 2023 01:51:51 +0200 Message-ID: <3e73ae5e-8550-42a7-82de-bea1ca57fe1e@igalia.com> Date: Mon, 7 Aug 2023 20:51:42 -0300 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 01/14] futex: Clarify FUTEX2 flags To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, dvhart@infradead.org, dave@stgolabs.net, Andrew Morton , urezki@gmail.com, hch@infradead.org, lstoakes@gmail.com, Arnd Bergmann , tglx@linutronix.de, linux-api@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, malteskarupke@web.de, axboe@kernel.dk References: <20230807121843.710612856@infradead.org> <20230807123322.814039156@infradead.org> Content-Language: en-US From: =?UTF-8?Q?Andr=C3=A9_Almeida?= In-Reply-To: <20230807123322.814039156@infradead.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 0C9991C0004 X-Rspam-User: X-Stat-Signature: 6utzmi1rjfhor9yw4zhihiyrdpo6yb9b X-Rspamd-Server: rspam01 X-HE-Tag: 1691452344-634717 X-HE-Meta: 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 n1MlRVJc 8wIGZWqhNvlwbQAbT1DrPXQQ0SBsnIXYNU7VFABoNfR18spoeo82uC7Pwc28V3q13qpE+e5J4uq0lPGE8NfABozfQDUY90yFWmAsphuJ1/CuXwdWTjPpSD2a0mmd4MR16wcspXzIds08E5dR1/qSjGeLV92hT690EukYKQZaApRMkcmrRmPMzk+a34heqb4tQoVrjxI59Aa8x8e3RsrTZfr/jqDw1Y0qRyCz9T1Fr1aJhKw/Q8kANHkMYsoRTA8Caqf8MyoEKyWJJYuCiUHNUrq9FKX64gnn5BIiObiry1ik60G6osuUaIgi73o46GDvAEu1nmSF+FxUxyJ+qMXNFai3KNfrIxxg5D98rJ8GTj5VHidRsqiwYtyanXgl0r+p1hG6NmpL7xac9fAt66DB0YBpgeZuqPunoDPq3OYGu8Gf9yos= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi Peter, thank you for your patches. Em 07/08/2023 09:18, Peter Zijlstra escreveu: > sys_futex_waitv() is part of the futex2 series (the first and only so > far) of syscalls and has a flags field per futex (as opposed to flags > being encoded in the futex op). > > This new flags field has a new namespace, which unfortunately isn't > super explicit. Notably it currently takes FUTEX_32 and > FUTEX_PRIVATE_FLAG. > > Introduce the FUTEX2 namespace to clarify this > > Signed-off-by: Peter Zijlstra (Intel) > Reviewed-by: Thomas Gleixner Reviewed-by: André Almeida > --- > include/uapi/linux/futex.h | 16 +++++++++++++--- > kernel/futex/syscalls.c | 7 +++---- > 2 files changed, 16 insertions(+), 7 deletions(-) > > --- a/include/uapi/linux/futex.h > +++ b/include/uapi/linux/futex.h > @@ -44,10 +44,20 @@ > FUTEX_PRIVATE_FLAG) > > /* > - * Flags to specify the bit length of the futex word for futex2 syscalls. > - * Currently, only 32 is supported. > + * Flags for futex2 syscalls. > */ > -#define FUTEX_32 2 > + /* 0x00 */ > + /* 0x01 */ > +#define FUTEX2_SIZE_U32 0x02 > + /* 0x04 */ > + /* 0x08 */ > + /* 0x10 */ > + /* 0x20 */ > + /* 0x40 */ > +#define FUTEX2_PRIVATE FUTEX_PRIVATE_FLAG > + > +/* do not use */ > +#define FUTEX_32 FUTEX2_SIZE_U32 /* historical accident :-( */ > > /* > * Max numbers of elements in a futex_waitv array > --- a/kernel/futex/syscalls.c > +++ b/kernel/futex/syscalls.c > @@ -183,8 +183,7 @@ SYSCALL_DEFINE6(futex, u32 __user *, uad > return do_futex(uaddr, op, val, tp, uaddr2, (unsigned long)utime, val3); > } > > -/* Mask of available flags for each futex in futex_waitv list */ > -#define FUTEXV_WAITER_MASK (FUTEX_32 | FUTEX_PRIVATE_FLAG) > +#define FUTEX2_VALID_MASK (FUTEX2_SIZE_U32 | FUTEX2_PRIVATE) > > /** > * futex_parse_waitv - Parse a waitv array from userspace > @@ -205,10 +204,10 @@ static int futex_parse_waitv(struct fute > if (copy_from_user(&aux, &uwaitv[i], sizeof(aux))) > return -EFAULT; > > - if ((aux.flags & ~FUTEXV_WAITER_MASK) || aux.__reserved) > + if ((aux.flags & ~FUTEX2_VALID_MASK) || aux.__reserved) > return -EINVAL; > > - if (!(aux.flags & FUTEX_32)) > + if (!(aux.flags & FUTEX2_SIZE_U32)) > return -EINVAL; > > futexv[i].w.flags = aux.flags; > >