From nobody Tue Jan 10 18:45:24 2023 X-Original-To: freebsd-hackers@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4Ns0BB6Y9dz2sQV6 for ; Tue, 10 Jan 2023 18:45:38 +0000 (UTC) (envelope-from asomers@gmail.com) Received: from mail-ua1-f51.google.com (mail-ua1-f51.google.com [209.85.222.51]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (2048 bits) client-digest SHA256) (Client CN "smtp.gmail.com", Issuer "GTS CA 1D4" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4Ns0B951xbz4DRp for ; Tue, 10 Jan 2023 18:45:37 +0000 (UTC) (envelope-from asomers@gmail.com) Authentication-Results: mx1.freebsd.org; dkim=none; spf=pass (mx1.freebsd.org: domain of asomers@gmail.com designates 209.85.222.51 as permitted sender) smtp.mailfrom=asomers@gmail.com; dmarc=none Received: by mail-ua1-f51.google.com with SMTP id z13so2014687uav.3 for ; Tue, 10 Jan 2023 10:45:37 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=to:subject:message-id:date:from:mime-version:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=wJcE7a3O1D/9Yz9caBtDZEyRxHrl4/2YxRCVTKD/mv8=; b=3NIgJBS2rrRhPNtQEwVHBwG57CX+Zku+czqQilw42T2RPtOu8OwkQ7BplWcQeuo8La BTChrowBM0x+00X5FHSR54EpYm7fjKjoxZ6RHY5PWbgzNRWEeXz08jmOE0oM71S02Gib 5vJI1QOAJCcqIVDw8FlBL9zyA1TxIVk9xYV9Dszzq/HeUxLrSYFZ/+UlNNzKeZQWNLGj bMQPkB7Wsbw9j7O5upWk8PBsUWC9NYhqwtz0SpinZkuXqAqG+XepC5bFRGIabyslYrTP 5cl1FwOhF8DgDqLot3/HUAOIWvMecvYHbGM/pI8bc6qkbzpHWl6qApgWcZx7oujE43ml /+rA== X-Gm-Message-State: AFqh2kqEM2Wr8Meiy4zXXepYKCqLRxazQLJGkpoD1cqRBf/YTLvQcris BaLCCRP/fysRCAEBTHpG7zmv/CqyMOM+Fc+aFo0iS/VS X-Google-Smtp-Source: AMrXdXtC1XN11Q6mXTnHqHirnr4a9omZY9cFHJYX39EVB2KhUyBpmJNjyWSjh0TFjojzaoptNDUM1Ws3Frm4FZs3E8U= X-Received: by 2002:ab0:58c2:0:b0:419:d3f0:d6a6 with SMTP id r2-20020ab058c2000000b00419d3f0d6a6mr7456111uac.111.1673376336064; Tue, 10 Jan 2023 10:45:36 -0800 (PST) List-Id: Technical discussions relating to FreeBSD List-Archive: https://lists.freebsd.org/archives/freebsd-hackers List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-hackers@freebsd.org MIME-Version: 1.0 From: Alan Somers Date: Tue, 10 Jan 2023 11:45:24 -0700 Message-ID: Subject: libcasper and async-signal-safety To: FreeBSD Hackers Content-Type: text/plain; charset="UTF-8" X-Spamd-Result: default: False [-1.25 / 15.00]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_MEDIUM(-1.00)[-1.000]; NEURAL_SPAM_SHORT(0.75)[0.746]; FORGED_SENDER(0.30)[asomers@freebsd.org,asomers@gmail.com]; R_SPF_ALLOW(-0.20)[+ip4:209.85.128.0/17]; MIME_GOOD(-0.10)[text/plain]; MLMMJ_DEST(0.00)[freebsd-hackers@freebsd.org]; MIME_TRACE(0.00)[0:+]; RWL_MAILSPIKE_POSSIBLE(0.00)[209.85.222.51:from]; ASN(0.00)[asn:15169, ipnet:209.85.128.0/17, country:US]; RCVD_IN_DNSWL_NONE(0.00)[209.85.222.51:from]; FREEMAIL_ENVFROM(0.00)[gmail.com]; R_DKIM_NA(0.00)[]; TO_DN_ALL(0.00)[]; RCVD_TLS_LAST(0.00)[]; RCPT_COUNT_ONE(0.00)[1]; FREEFALL_USER(0.00)[asomers]; RCVD_COUNT_TWO(0.00)[2]; ARC_NA(0.00)[]; FROM_NEQ_ENVFROM(0.00)[asomers@freebsd.org,asomers@gmail.com]; FROM_HAS_DN(0.00)[]; PREVIOUSLY_DELIVERED(0.00)[freebsd-hackers@freebsd.org]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DMARC_NA(0.00)[freebsd.org]; TO_DOM_EQ_FROM_DOM(0.00)[] X-Rspamd-Queue-Id: 4Ns0B951xbz4DRp X-Spamd-Bar: - X-ThisMailContainsUnwantedMimeParts: N Normally when a multithreaded process forks, the child is restricted to only calling async-signal-safe functions until it exec()s.. Otherwise, bad stuff could happen like deadlocks on mutexes that will never be released. The cap_init(3) function, used to create Casper services, forks (and then its child forks again and again and again). But there's nothing in the libcasper_service(3) man page about async-signal-safety. I assume that this is just an oversight. After all, all of the existing programs in the base system that use casper are single-threaded. But it's a limitation that ought to be documented in the cap_init(3) man page, right? Or am I missing something? -Alan