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b=VGYK35XjgnDbwp9myvCNunLYiZ ONqbtVc+b9MSgQ8Cs0BFBv4LXdEFY6rWnjnzCUnI1IJHTrFV4DBa9NCNIC+/W2Uc2U4dtrKtboDjU GiCdwuKUu7ezWdbzani+5BULnp7q7SV7xivaGmDlz9f/5JTG2MIVoIVvFre7D1+hcMII/vZc88NDB KWYXrDGUIRAAWDGuhYRaRsuBNtqJaUrtGpoPikDsdAHsBJ3d4rVAngQO5VTrj62QQzF9Sv5L1o0Hp dU//5DCEHJv6c+6smSKVkS1ldBuwH79lmGVqxwckHJakExJAuVMztrljCj3/lTaFSrj6xHmdXw7f8 3FCnnnJQ==; Received: from [189.78.222.89] (helo=[192.168.15.100]) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_128_GCM:128) (Exim) id 1t4RmV-00FAr4-MJ; Fri, 25 Oct 2024 23:23:39 +0200 Message-ID: <4b9a5824-7cb7-4dc6-91dd-536f4dad9771@igalia.com> Date: Fri, 25 Oct 2024 18:23:33 -0300 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/6] futex: Implement FUTEX2_NUMA 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 , linux-api@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, malteskarupke@web.de, cl@linux.com, llong@redhat.com, tglx@linutronix.de References: <20241025090347.244183920@infradead.org> <20241025093944.485691531@infradead.org> Content-Language: en-US From: =?UTF-8?Q?Andr=C3=A9_Almeida?= In-Reply-To: <20241025093944.485691531@infradead.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: hgaawf5s7mku5ifeaprnf64rbraqjnni X-Rspamd-Queue-Id: 27C69120005 X-Rspamd-Server: rspam11 X-HE-Tag: 1729891417-463933 X-HE-Meta: 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 ObUk6z+K A/8nsKil8WeDxVHD/pOLx898PC5JEto9OmfIF6Wwpv0C3xItZupTkbyKFzV9X7pz8MHV1OEUJu127y3ou0st2MeyZ3YS09TmQaUAE5PhrH7oQ6Y7H6MdDOY9+MVJelQS6CmkkxA7ugOVpP0b/uV/rjx99Ly0+IQWON6RGL/OuRtjkvAZSqiNu6XPIvDp7Kl5tLJNtimaV0jlmZBXDz9Zohs9TwM5DnkkTB8438ReEo4TTkn6cc+ZW2/NzVSkjnoVsHdEYr3ZgXAcJgWqTRWJ3ZEOYC/zsXT1EYapw81RroTf1WWDuatHYtjm0jBTe+nmz80iEGT8Y/TK9mLh6ChewWcvJj6YC1ZFfdNikvDdfCgPwDR1cOkw2brhie7C0d/dbLQHmd4BDo23nxXg= 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: List-Subscribe: List-Unsubscribe: Hey Peter, Em 25/10/2024 06:03, Peter Zijlstra escreveu: > Extend the futex2 interface to be numa aware. > > When FUTEX2_NUMA is specified for a futex, the user value is extended > to two words (of the same size). The first is the user value we all > know, the second one will be the node to place this futex on. > > struct futex_numa_32 { > u32 val; > u32 node; > }; > Maybe this should live at include/uapi/linux/futex.h. > When node is set to ~0, WAIT will set it to the current node_id such > that WAKE knows where to find it. If userspace corrupts the node value > between WAIT and WAKE, the futex will not be found and no wakeup will > happen. > > When FUTEX2_NUMA is not set, the node is simply an extention of the > hash, such that traditional futexes are still interleaved over the > nodes. > > This is done to avoid having to have a separate !numa hash-table. > > Signed-off-by: Peter Zijlstra (Intel) Do you think some of those changes should be guarded with #ifdef CONFIG_NUMA? Or is fine as it is? I see that most of NUMA_ values defines to 1 anyway on !numa, but maybe the futex_init() and futex_hash() would be a bit more simplified. [...] > > +static int futex_get_value(u32 *val, u32 __user *from, unsigned int flags) > +{ > + switch (futex_size(flags)) { > + case 1: return __get_user(*val, (u8 __user *)from); > + case 2: return __get_user(*val, (u16 __user *)from); > + case 4: return __get_user(*val, (u32 __user *)from); > + default: BUG(); > + } > +} > + > +static int futex_put_value(u32 val, u32 __user *to, unsigned int flags) > +{ > + switch (futex_size(flags)) { > + case 1: return __put_user(val, (u8 __user *)to); > + case 2: return __put_user(val, (u16 __user *)to); > + case 4: return __put_user(val, (u32 __user *)to); > + default: BUG(); > + } > +} > + I found a bit confusing that this is here, shouldn't be at [PATCH 4/6] futex: Enable FUTEX2_{8,16}?