From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-14.4 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1,WEIRD_QUOTING autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 390F1C4338F for ; Thu, 29 Jul 2021 10:18:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 17A6960E09 for ; Thu, 29 Jul 2021 10:18:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235546AbhG2KSO (ORCPT ); Thu, 29 Jul 2021 06:18:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56788 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235155AbhG2KSN (ORCPT ); Thu, 29 Jul 2021 06:18:13 -0400 Received: from mail-wr1-x434.google.com (mail-wr1-x434.google.com [IPv6:2a00:1450:4864:20::434]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 58B44C061757 for ; Thu, 29 Jul 2021 03:18:10 -0700 (PDT) Received: by mail-wr1-x434.google.com with SMTP id c16so6220814wrp.13 for ; Thu, 29 Jul 2021 03:18:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:from:to:cc:references:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=5mP9n3Bdu7WIrcqdSTML1Va0ccYxxJeK+1v6RllqZ/k=; b=cmxqV15AI7O9rIHI1Yd8+tniX1HqH0JSI5fKsgaRUlZW5TPHX4SjgrECpYNBr0qSA8 rwYY+3B8Z4iZt0ztIj1TYuMHjVKYtpUYm2+A0QeaWgydb/rBEhZy3S5sIbLX3wrqcWFP nJHG8vPiT6Q4EXYz0zyJInd+C10ibmUf3yVpX1jti5XU29Qg7aSwZLUR8ixMwAqL7Uwq t4MRb0fLPpfLUws26RpkFpvLB7LEgZjYPrHRkW/buR8AsQnMKaxT/wmBWHsrwnN8NDCq Z6VQs4p2P2VtmGzrTbi38gSGkv0Ar9zvIaWzV4OYJtwirawNAW3NF2alg+WnZZdkE+mo 2ADw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:from:to:cc:references:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=5mP9n3Bdu7WIrcqdSTML1Va0ccYxxJeK+1v6RllqZ/k=; b=Ri0V6ofvwVNt9IrkbrEu4/GvHupd4HKREg9fiCRDrrlcjLoaIB0Kya6VySQChSExCm ihMYIW/YBw3umqK80NlmCr8GPj7TgDygiQZCyvcZ1sUZ6pUe+WQDqjcQDuiCFZyzQvWl SlG3Uo9fKN4AiHZ12eczd3YRInH62lLeaWNYf94FyvLUmvhAgq0YLxqWRPmviU8BngcL Dw/SKwbriJh6izJOt5/KQf9dxUyBfQQVtR03r1w42ZY+U1KT2q+kFv78fKMWZl8D3/yH zDcRN4/1YRl+8TVx8mECI9afCgUNrfMm4MjcGqf5lyPGJG+X+1kN4v4AFVsPHoggShQY 1e+g== X-Gm-Message-State: AOAM530KvFncMEafVPSd6B+BGsStv2FHke7VdhiOd+FIPoKjpPmaqO7Y rW5pSx2JVW6eqFI0oalRCjocejhphyU= X-Google-Smtp-Source: ABdhPJxd/8WFl3uPseUhVxhn122BgeURKqKEX5vb8TZ9TviOuM1ulLcHseiLQDATdG3cqQjZsxC6kA== X-Received: by 2002:a5d:690e:: with SMTP id t14mr3972455wru.258.1627553888895; Thu, 29 Jul 2021 03:18:08 -0700 (PDT) Received: from [10.8.0.150] ([195.53.121.100]) by smtp.gmail.com with ESMTPSA id v15sm9357514wmj.39.2021.07.29.03.18.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 29 Jul 2021 03:18:08 -0700 (PDT) Subject: Re: [PATCH 10/32] futex.2: Document FUTEX_LOCK_PI2 From: "Alejandro Colomar (man-pages)" To: mtk.manpages@gmail.com Cc: Kurt Kanzenbach , linux-man@vger.kernel.org References: <20210728202008.3158-1-alx.manpages@gmail.com> <20210728202008.3158-11-alx.manpages@gmail.com> Message-ID: Date: Thu, 29 Jul 2021 12:18:07 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210728202008.3158-11-alx.manpages@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-man@vger.kernel.org Hi Michael, On 7/28/21 10:19 PM, Alejandro Colomar wrote: > From: Kurt Kanzenbach > > FUTEX_LOCK_PI2 is a new futex operation which was recently introduced into the > Linux kernel. It works exactly like FUTEX_LOCK_PI. However, it has support for > selectable clocks for timeouts. By default CLOCK_MONOTONIC is used. If > FUTEX_CLOCK_REALTIME is specified then the timeout is measured against > CLOCK_REALTIME. > > This new operation addresses an inconsistency in the futex interface: > FUTEX_LOCK_PI only works with timeouts based on CLOCK_REALTIME in contrast to > all the other PI operations. > > Document the FUTEX_LOCK_PI2 command. > > Signed-off-by: Kurt Kanzenbach Please drop this one. I just found a small typo, and will add a Reviewed-by line received today. Thanks, Alex > --- > man2/futex.2 | 53 ++++++++++++++++++++++++++++++++++++++++++++++++---- > 1 file changed, 49 insertions(+), 4 deletions(-) > > diff --git a/man2/futex.2 b/man2/futex.2 > index ada96c517..2f340e0e0 100644 > --- a/man2/futex.2 > +++ b/man2/futex.2 > @@ -241,10 +241,13 @@ and so on. > This option bit can be employed only with the > .BR FUTEX_WAIT_BITSET , > .BR FUTEX_WAIT_REQUEUE_PI , > -and > (since Linux 4.5) > .\" commit 337f13046ff03717a9e99675284a817527440a49 > -.BR FUTEX_WAIT > +.BR FUTEX_WAIT , > +and > +(since Linux v5.14.0) > +.\" commit bf22a6976897977b0a3f1aeba6823c959fc4fdae > +.BR FUTEX_LOCK_PI2 > operations. > .IP > If this option is set, the kernel measures the > @@ -904,7 +907,9 @@ value to 0 if the previous value was the expected TID. > If a futex is already acquired (i.e., has a nonzero value), > waiters must employ the > .B FUTEX_LOCK_PI > -operation to acquire the lock. > +or > +.B FUTEX_LOCK_PI2 > +operations to acquire the lock. > If other threads are waiting for the lock, then the > .B FUTEX_WAITERS > bit is set in the futex value; > @@ -964,6 +969,8 @@ Note that the PI futex operations must be used as paired operations > and are subject to some additional requirements: > .IP * 3 > .B FUTEX_LOCK_PI > +, > +.B FUTEX_LOCK_PI2 > and > .B FUTEX_TRYLOCK_PI > pair with > @@ -1122,6 +1129,27 @@ arguments are ignored. > .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" > .\" > .TP > +.BR FUTEX_LOCK_PI2 " (since Linux 5.14.0)" > +.\" commit bf22a6976897977b0a3f1aeba6823c959fc4fdae > +This operation works similar like > +.BR FUTEX_LOCK_PI . > +The only difference is the > +timeout argument. > +.BR FUTEX_LOCK_PI2 > +has support for selectable clocks. > +.IP > +If > +.I timeout > +is not NULL, the structure it points to specifies > +an absolute timeout. > +If > +.I timeout > +is NULL, the operation can block indefinitely. > +.IP > +.\" > +.\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" > +.\" > +.TP > .BR FUTEX_TRYLOCK_PI " (since Linux 2.6.18)" > .\" commit c87e2837be82df479a6bae9f155c43516d2feebc > This operation tries to acquire the lock at > @@ -1168,6 +1196,8 @@ arguments are ignored. > .\" commit c87e2837be82df479a6bae9f155c43516d2feebc > This operation wakes the top priority waiter that is waiting in > .B FUTEX_LOCK_PI > +or > +.B FUTEX_LOCK_PI2 > on the futex address provided by the > .I uaddr > argument. > @@ -1379,6 +1409,9 @@ Returns the number of waiters that were woken up. > .B FUTEX_LOCK_PI > Returns 0 if the futex was successfully locked. > .TP > +.B FUTEX_LOCK_PI2 > +Returns 0 if the futex was successfully locked. > +.TP > .B FUTEX_TRYLOCK_PI > Returns 0 if the futex was successfully locked. > .TP > @@ -1435,6 +1468,7 @@ is not equal to the expected value > .TP > .BR EAGAIN > .RB ( FUTEX_LOCK_PI , > +.BR FUTEX_LOCK_PI2 , > .BR FUTEX_TRYLOCK_PI , > .BR FUTEX_CMP_REQUEUE_PI ) > The futex owner thread ID of > @@ -1448,6 +1482,7 @@ Try again. > .TP > .BR EDEADLK > .RB ( FUTEX_LOCK_PI , > +.BR FUTEX_LOCK_PI2 , > .BR FUTEX_TRYLOCK_PI , > .BR FUTEX_CMP_REQUEUE_PI ) > The futex word at > @@ -1536,11 +1571,14 @@ The kernel detected an inconsistency between the user-space state at > .I uaddr > and the kernel state\(emthat is, it detected a waiter which waits in > .BR FUTEX_LOCK_PI > +or > +.BR FUTEX_LOCK_PI2 > on > .IR uaddr . > .TP > .B EINVAL > .RB ( FUTEX_LOCK_PI , > +.BR FUTEX_LOCK_PI2 , > .BR FUTEX_TRYLOCK_PI , > .BR FUTEX_UNLOCK_PI ) > The kernel detected an inconsistency between the user-space state at > @@ -1590,6 +1628,8 @@ that is, the kernel detected a waiter which waits on > .I uaddr > via > .BR FUTEX_LOCK_PI > +or > +.BR FUTEX_LOCK_PI2 > (instead of > .BR FUTEX_WAIT_REQUEUE_PI ). > .TP > @@ -1618,6 +1658,7 @@ The system-wide limit on the total number of open files has been reached. > .TP > .BR ENOMEM > .RB ( FUTEX_LOCK_PI , > +.BR FUTEX_LOCK_PI2 , > .BR FUTEX_TRYLOCK_PI , > .BR FUTEX_CMP_REQUEUE_PI ) > The kernel could not allocate memory to hold state information. > @@ -1634,11 +1675,13 @@ option was specified in > but the accompanying operation was neither > .BR FUTEX_WAIT , > .BR FUTEX_WAIT_BITSET , > +.BR FUTEX_WAIT_REQUEUE_PI , > nor > -.BR FUTEX_WAIT_REQUEUE_PI . > +.BR FUTEX_LOCK_PI2 . > .TP > .BR ENOSYS > .RB ( FUTEX_LOCK_PI , > +.BR FUTEX_LOCK_PI2 , > .BR FUTEX_TRYLOCK_PI , > .BR FUTEX_UNLOCK_PI , > .BR FUTEX_CMP_REQUEUE_PI , > @@ -1649,6 +1692,7 @@ are not supported on some CPU variants. > .TP > .BR EPERM > .RB ( FUTEX_LOCK_PI , > +.BR FUTEX_LOCK_PI2 , > .BR FUTEX_TRYLOCK_PI , > .BR FUTEX_CMP_REQUEUE_PI ) > The caller is not allowed to attach itself to the futex at > @@ -1665,6 +1709,7 @@ The caller does not own the lock represented by the futex word. > .TP > .BR ESRCH > .RB ( FUTEX_LOCK_PI , > +.BR FUTEX_LOCK_PI2 , > .BR FUTEX_TRYLOCK_PI , > .BR FUTEX_CMP_REQUEUE_PI ) > The thread ID in the futex word at > -- Alejandro Colomar Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/ http://www.alejandro-colomar.es/