Date: Wed, 05 Apr 2017 00:21:21 -0700 (PDT) From: "Mould making/Precision stamping/ Machining parts Supply (via Google Photos)" <noreply-1a925d0d6666deae07b758152a56780a@google.com> To: freebsd-questions@freebsd.org Subject: Mould making/Precision stamping/ Machining parts Supply shared 1 photo with you Message-ID: <BdBm-cS1iceWy9b-GdDm5Q@notifications.google.com>
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Wed, 5 Apr 2017 09:19:53 +0000 (UTC) (envelope-from ablacktshirt@gmail.com) Received: from mail-pf0-x22c.google.com (mail-pf0-x22c.google.com [IPv6:2607:f8b0:400e:c00::22c]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id E1EBBD5B for <freebsd-questions@freebsd.org>; Wed, 5 Apr 2017 09:19:52 +0000 (UTC) (envelope-from ablacktshirt@gmail.com) Received: by mail-pf0-x22c.google.com with SMTP id 197so4744468pfv.1 for <freebsd-questions@freebsd.org>; Wed, 05 Apr 2017 02:19:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to; bh=j4wiShF3kVx7eHoJ9ZeXDIjE4L84IaYPQXMic7ZMrDQ=; b=M64JqE4F5V4Wtv79ReQ74U1racO74gnmHNPqaYg7MihVfGWSma7PPhXdB2JZDhCZT0 Wkd9dy6h36Q0vW7oElFc6MUjHuirDE9vQ4INBWTWxgE82gItEJKSQfScLM6yL+cFBXrp QxDD/0zVLSCnmmEeuuhdMQjplcZMJy9Vj2tdCYQajQsl9wWqOZkbhVK/Lgd4TB6nJNLy oa6BqA60GvPmkS9vBXOiBBQgEgwFiTsv3uDXRnb6W25a8qwWN0N/W6GP85dyxhlIGWo0 kbwtxJJbLolI3+s7Z9QZj9Nyr3Txx/wAUcX9V3hUsTNfmscwTNqXO/968eQLWMXZ9N6f yzfQ== X-Google-DKIM-Signature: v=1; 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charset=UTF-8 X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: User questions <freebsd-questions.freebsd.org> List-Unsubscribe: <https://lists.freebsd.org/mailman/options/freebsd-questions>, <mailto:freebsd-questions-request@freebsd.org?subject=unsubscribe> List-Archive: <http://lists.freebsd.org/pipermail/freebsd-questions/>; List-Post: <mailto:freebsd-questions@freebsd.org> List-Help: <mailto:freebsd-questions-request@freebsd.org?subject=help> List-Subscribe: <https://lists.freebsd.org/mailman/listinfo/freebsd-questions>, <mailto:freebsd-questions-request@freebsd.org?subject=subscribe> X-List-Received-Date: Wed, 05 Apr 2017 09:19:53 -0000 All right seems like that this list is not a right place for this kind of problem. Any suggestion on the right mailing list to send? regards, yubinr 2017-04-03 0:30 GMT+08:00 Yubin Ruan <ablacktshirt@gmail.com>: > Hi, > I am reading the FreeBSD source code related to its locking mechanism. I > have done some researches but still cannot understand some codes. > > Let's take `spinlock' for example. I know there are different kinds of > mutex in FreeBSD: spin mutex and other kinds of mutex. I try to locate > the source of spin mutex but what I find all look very weird to me. For > example, the `spinlock_enter()` > > 1816 void > 1817 spinlock_enter(void) > 1818 { > 1819 struct thread *td; > 1820 register_t flags; > 1821 > 1822 td = curthread; > 1823 if (td->td_md.md_spinlock_count == 0) { > 1824 flags = intr_disable(); > 1825 td->td_md.md_spinlock_count = 1; > 1826 td->td_md.md_saved_flags = flags; > 1827 } else > 1828 td->td_md.md_spinlock_count++; > 1829 critical_enter(); > 1830 } > > Does this function provides the ordinary "spinlock" functionality? There > is no special "test-and-set" instruction, and neither any extra locking > to protect internal data structure manipulation. Isn't this subjected to > race condition? > > I also checked the `mtx_lock()`, but neither can't find a seemingly > correct implementation. > > Do I miss anything? Which is the real implementation of the spin lock in > FreeBSD? > > Thanks > Yubin Ruan
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