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Received: from [191.193.179.209] (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 1qTrcL-00GDvY-H2; Thu, 10 Aug 2023 00:25:25 +0200 Message-ID: <071c02ae-a74d-46d8-990b-262264b62caf@igalia.com> Date: Wed, 9 Aug 2023 19:25:19 -0300 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 05/14] futex: Add sys_futex_wake() To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, dvhart@infradead.org, dave@stgolabs.net, tglx@linutronix.de, axboe@kernel.dk, 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, Geert Uytterhoeven References: <20230807121843.710612856@infradead.org> <20230807123323.090897260@infradead.org> Content-Language: en-US From: =?UTF-8?Q?Andr=C3=A9_Almeida?= In-Reply-To: <20230807123323.090897260@infradead.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 917FFA0024 X-Stat-Signature: 9rr5peq4r764id8nrmwcdudj1u9uehuu X-HE-Tag: 1691619953-496525 X-HE-Meta: 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 A56jsfF2 nR0WpK8mjn7wIMi6T1jncZFUCjtrmb0zuCK3LNxoYTag8UaJOq3ynLjFsocw9d/Fz++HwYuwOGPC6SBwVyru1ZIvT9aaKNMW1PY9F+zB8mi5sxDF/jqJ7mhYhHwsvh3P6EUvQ6E39hMv2OYEnKQZj9q2t0eFByKHi01Om4iM3dAHl1BehDkO2aszhCyUrvn4qNsrBQLhaMsh5XzVIcPeVFdONd2wqjrdTm4Zism8cFOX1o58mr0LqCkjrucfklr/QlX4xPU0sSdVoHgwvSQn2yDyLB7ubEJFJJWbtZcxyi3alcZfSShIQIVCTJy2Swdk2H6rYH2x0433k4jXMVM49W2sPY9c6l3DQ1iipRus5nuWwLNyFT9deiMsVcoRkwjT/FmC96Rw6n/0Iu7dNwQhL07Zo8LE53QxjmzgzOL0cKpmjMMA7s+hRX+Mhm5iASFUP+usM9/2CQjydgmBQeLmJtNqcdA== 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, Em 07/08/2023 09:18, Peter Zijlstra escreveu: > To complement sys_futex_waitv() add sys_futex_wake(). This syscall > implements what was previously known as FUTEX_WAKE_BITSET except it > uses 'unsigned long' for the bitmask and takes FUTEX2 flags. > > The 'unsigned long' allows FUTEX2_SIZE_U64 on 64bit platforms. > > Signed-off-by: Peter Zijlstra (Intel) > Acked-by: Geert Uytterhoeven > --- [...] > +/* > + * sys_futex_wake - Wake a number of futexes > + * @uaddr: Address of the futex(es) to wake > + * @mask: bitmask > + * @nr: Number of the futexes to wake > + * @flags: FUTEX2 flags > + * > + * Identical to the traditional FUTEX_WAKE_BITSET op, except it is part of the > + * futex2 family of calls. > + */ > + > +SYSCALL_DEFINE4(futex_wake, > + void __user *, uaddr, > + unsigned long, mask, > + int, nr, > + unsigned int, flags) > +{ Do you think we could have a if (!nr) return 0; here? Otherwise, calling futex_wake(&f, 0, flags) will wake 1 futex (if available), which is a strange undocumented behavior in my opinion. > + if (flags & ~FUTEX2_VALID_MASK) > + return -EINVAL; > + > + flags = futex2_to_flags(flags); > + if (!futex_flags_valid(flags)) > + return -EINVAL; > + > + if (!futex_validate_input(flags, mask)) > + return -EINVAL; > + > + return futex_wake(uaddr, flags, nr, mask); > +} > + > #ifdef CONFIG_COMPAT > COMPAT_SYSCALL_DEFINE2(set_robust_list, > struct compat_robust_list_head __user *, head, > --- a/kernel/sys_ni.c > +++ b/kernel/sys_ni.c > @@ -87,6 +87,7 @@ COND_SYSCALL_COMPAT(set_robust_list); > COND_SYSCALL(get_robust_list); > COND_SYSCALL_COMPAT(get_robust_list); > COND_SYSCALL(futex_waitv); > +COND_SYSCALL(futex_wake); > COND_SYSCALL(kexec_load); > COND_SYSCALL_COMPAT(kexec_load); > COND_SYSCALL(init_module); > >