From owner-freebsd-hackers@freebsd.org Tue Aug 21 13:38:04 2018 Return-Path: Delivered-To: freebsd-hackers@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 8DD9F1072909 for ; Tue, 21 Aug 2018 13:38:04 +0000 (UTC) (envelope-from jacques.fourie@gmail.com) Received: from mail-io0-x233.google.com (mail-io0-x233.google.com [IPv6:2607:f8b0:4001:c06::233]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 2718283B99 for ; Tue, 21 Aug 2018 13:38:04 +0000 (UTC) (envelope-from jacques.fourie@gmail.com) Received: by mail-io0-x233.google.com with SMTP id l7-v6so15385547iok.6 for ; Tue, 21 Aug 2018 06:38:04 -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 :cc; bh=slagwyBMQO89dIeDSC73D4kUZvviZrNpN0FYVpoF+Cc=; b=tpKeQD1559WFrtA3NlMaWRzd9C+bCifu272Bw8u+BMayTCMKU7UJD7vPwdAu6Pt3Fn QyRM3VV4d2VMt7cMCAVFUOolza7H4oxKvB0ZRYezskujiXy7QuCpwdsb4tdYh9AbXRP/ Zdnj8ffloj4+74EzWAPLwTa2nXXY3y5MLBjHmMUlQVrVkUfvrsKdwcbLUzr8PIxt0Xkf TFjh5tX1X039mm1Tk1VOfdUfLJsOD/oSyWZFiXrKpZDXhH3JtTaFh711rMkQdziLwzwa DpDwKXCZm4/KYPpa+X/v3Ua58gStHaHQE1QDnFk3q37pQXulkRG31Uv23dQt24oX7txj 8mkg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=slagwyBMQO89dIeDSC73D4kUZvviZrNpN0FYVpoF+Cc=; b=k7d9AErqZPufYSRiOpoENjDiqJtSvY6LUkKNLVhTPhq0tfCpWsdkGB42IqKGQItfrM 2PUQRdgyPY6rPJSReaTG1laAi4dRUwvQtJ37pVrLCi/KkDItuhGH5dCw/NxkWWOig/+s zHLyWUoQFbQ9ivoLckd0Dl9Wq5ASv4Vzs7NmD8x7fU5GzChekA7wFiQvEirslUeK1Fq/ hLaVbJwIsmzmX1u/E9QueS4YECfCXb5z5vnmMb8B4a1lh9brlZAZxmIYlnEmaYChwZc1 taUT07XhpD1q2Vq+9+1zvcVEOHhtDgJAL5GHkdYiHLwXSVdZRUGVLhFrS6SAA5LG4QD1 I90g== X-Gm-Message-State: APzg51BV5av7BBP0yBQZFRfCf+dULP/u8WJXrGHqvERNk+aarOSjeen6 Yvk9e10W6Nuzi4ev+Ke1CmegputvdLiO4FsFR1ngNmsO X-Google-Smtp-Source: ANB0VdYjLTDHxmoYiIbjZTzaAWJg6jeTEU73s36b6z4alMgkAqj0tWM4oQawQ7yCx/0WMweenQBKXyjmQXj1gfJSsak= X-Received: by 2002:a6b:b7c7:: with SMTP id h190-v6mr5822687iof.164.1534858683585; Tue, 21 Aug 2018 06:38:03 -0700 (PDT) MIME-Version: 1.0 Received: by 2002:a6b:d611:0:0:0:0:0 with HTTP; Tue, 21 Aug 2018 06:38:03 -0700 (PDT) In-Reply-To: References: From: Jacques Fourie Date: Tue, 21 Aug 2018 09:38:03 -0400 Message-ID: Subject: Re: epoch(9) background information? To: Sebastian Huber Cc: FreeBSD Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Content-Filtered-By: Mailman/MimeDel 2.1.27 X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.27 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 21 Aug 2018 13:38:04 -0000 On Tue, Aug 21, 2018 at 8:33 AM, Sebastian Huber < sebastian.huber@embedded-brains.de> wrote: > Hello, > > I update currently a port of the FreeBSD network stack, etc. to the > real-time operating system RTEMS from the head version at 2017-04-04 to t= he > head version of today. I noticed that some read-write locks are replaced = by > a relatively new stuff called EPOCH(9). Is there some background > information available for this? The man page is a bit vague and searching > for something named epoch on the internet is not really great. For exampl= e, > what is the motivation for this change? How is this related to > read-copy-update (RCU)? > > -- > Sebastian Huber, embedded brains GmbH > > Address : Dornierstr. 4, D-82178 Puchheim, Germany > > Phone : +49 89 189 47 41-16 > Fax : +49 89 189 47 41-09 > E-Mail : sebastian.huber@embedded-brains.de > PGP : Public key available on request. > > Diese Nachricht ist keine gesch=C3=A4ftliche Mitteilung im Sinne des EHUG= . > > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org= " > Additional information is available here : http://concurrencykit.org/pr esentations/ebr.pdf. The way I understand it is that it is mostly used in place of read locks to provide liveness guarantees without using atomics. Additional detail is available in the commit messages. As an example see r333813 for some performance data.