From nobody Fri Sep 02 14:11:40 2022 X-Original-To: freebsd-current@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 4MK0G81rfKz4Zh2B for ; Fri, 2 Sep 2022 14:11:44 +0000 (UTC) (envelope-from mjguzik@gmail.com) Received: from mail-lj1-x22d.google.com (mail-lj1-x22d.google.com [IPv6:2a00:1450:4864:20::22d]) (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 4MK0G74TxZz3GMv for ; Fri, 2 Sep 2022 14:11:43 +0000 (UTC) (envelope-from mjguzik@gmail.com) Received: by mail-lj1-x22d.google.com with SMTP id r27so1974124ljn.0 for ; Fri, 02 Sep 2022 07:11:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=cc:to:subject:message-id:date:from:references:in-reply-to :mime-version:from:to:cc:subject:date; bh=L+DOZd8lKYgIiKDKlg25yb0PeJlqQWAFsATC84UgqRw=; b=Py6JNccxbGkO1hzsTkjgg3LCsYjHF8jXBoxOu/LftJgIYW0FNR0l84Jebe6B9mHceI 45AGKLVTNCdTQEazM4TnVl8uOqTKJPyt2+im53PJ14bTW4+vID24jue81eDo7opHyTRN Mx7gDZwRT8pCfY1tYp5n0bVHAP+o9Mo97k+6TMtPXK9j70TsclhsMuJSzIkyXEy2eQ68 moqAdKJRbRklNJIdVGHXZjW5uFojK0GoGC8HJsvnL+0rPm1I2CuFUr5FjGM8ozp7s3Iz F2TaMYzEciq6wYunEQqXu4wKwVN/nFG8xV9KYEMjlUxdtSVXO3TW+yxKUlGbyCQ4mlJ9 Gh3w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:references:in-reply-to :mime-version:x-gm-message-state:from:to:cc:subject:date; bh=L+DOZd8lKYgIiKDKlg25yb0PeJlqQWAFsATC84UgqRw=; b=y/xg9LKc5I/VVO2htjEHOOzwxfShJYySophVwfpKCMRww8zCQTSs5pqZCuOqPzR2DA N8PK/C+IKnVpAY4sC6hqi/+SI+V6Sgv4j8eDexH3lptfMrgqkbtX1Widzf/bY0jzbwv/ 84NqPm/vndcqOr/cRX2GnSaRZg70jXlQoVCv/c8p7XEHPtYKwIyNBzBoaI8wsc9vsZTO Qfk5gKDmnKXshrJebGZ+iEQBgSwdTU/WJDwOg9SWU9OqDtJNmv0Ct9sODGO3lrFaRl3W CLL+exs8KsW+//wFdJvwnEPEGMB4SEwX5n1zkxkdahXiKqWM0gdu5Dmw0a7P7jFLrUHm gNHg== X-Gm-Message-State: ACgBeo0H6OQ5MqJxxg6I3/LVnpkn+YhfNWirPHBB224L6oYRRKI66BkS 1somCkASli6TQ5lSeaj+1Wp1RPFg7dmoNPFFl/RHv/TG X-Google-Smtp-Source: AA6agR4BLdV4KZ3yZRK5QhV+VXeCOZFEToZ4TzPemPU0l6iV+rMFlf9EMYUchRo419h+wsweEi5N7FePmJ6aaUkNVls= X-Received: by 2002:a2e:aa1c:0:b0:268:fd46:e590 with SMTP id bf28-20020a2eaa1c000000b00268fd46e590mr432887ljb.206.1662127901673; Fri, 02 Sep 2022 07:11:41 -0700 (PDT) List-Id: Discussions about the use of FreeBSD-current List-Archive: https://lists.freebsd.org/archives/freebsd-current List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-current@freebsd.org MIME-Version: 1.0 Received: by 2002:a05:6520:14d:b0:211:6cae:be17 with HTTP; Fri, 2 Sep 2022 07:11:40 -0700 (PDT) In-Reply-To: References: From: Mateusz Guzik Date: Fri, 2 Sep 2022 16:11:40 +0200 Message-ID: Subject: Re: kernel-side thread stack swapping To: Konstantin Belousov Cc: freebsd-current@freebsd.org Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 4MK0G74TxZz3GMv X-Spamd-Bar: -- Authentication-Results: mx1.freebsd.org; dkim=pass header.d=gmail.com header.s=20210112 header.b=Py6JNccx; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (mx1.freebsd.org: domain of mjguzik@gmail.com designates 2a00:1450:4864:20::22d as permitted sender) smtp.mailfrom=mjguzik@gmail.com X-Spamd-Result: default: False [-2.40 / 15.00]; NEURAL_HAM_MEDIUM(-0.98)[-0.977]; DMARC_POLICY_ALLOW(-0.50)[gmail.com,none]; NEURAL_HAM_SHORT(-0.42)[-0.418]; R_SPF_ALLOW(-0.20)[+ip6:2a00:1450:4000::/36:c]; R_DKIM_ALLOW(-0.20)[gmail.com:s=20210112]; MIME_GOOD(-0.10)[text/plain]; FREEMAIL_TO(0.00)[gmail.com]; RCVD_IN_DNSWL_NONE(0.00)[2a00:1450:4864:20::22d:from]; MLMMJ_DEST(0.00)[freebsd-current@freebsd.org]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; FROM_EQ_ENVFROM(0.00)[]; ASN(0.00)[asn:15169, ipnet:2a00:1450::/32, country:US]; FREEMAIL_ENVFROM(0.00)[gmail.com]; RCPT_COUNT_TWO(0.00)[2]; MID_RHS_MATCH_FROMTLD(0.00)[]; RCVD_TLS_LAST(0.00)[]; TO_DN_SOME(0.00)[]; FROM_HAS_DN(0.00)[]; DKIM_TRACE(0.00)[gmail.com:+]; FREEMAIL_FROM(0.00)[gmail.com]; RCVD_COUNT_THREE(0.00)[3]; PREVIOUSLY_DELIVERED(0.00)[freebsd-current@freebsd.org]; TO_MATCH_ENVRCPT_SOME(0.00)[]; DWL_DNSWL_NONE(0.00)[gmail.com:dkim] X-ThisMailContainsUnwantedMimeParts: N On 9/2/22, Konstantin Belousov wrote: > On Fri, Sep 02, 2022 at 02:05:37PM +0200, Mateusz Guzik wrote: >> Is this really of practical use today? >> >> I have a WIP patch which needs to temporarily store something on the >> stack and should things go wrong enough it will be accessed by UMA, >> which can't handle the fault nor decide to skip the access. >> >> I can add something like td_pinstack or whatever to keep it around, >> but perhaps the entire machinery can be just whacked? > p_hold already does that. > I only need to protect the one stack and more importantly don't want to take the proc lock to bump p_hold (nor convert it to atomics), it's all thread-local so to speak. -- Mateusz Guzik