From owner-freebsd-python@freebsd.org Fri Dec 21 16:52:45 2018 Return-Path: <owner-freebsd-python@freebsd.org> Delivered-To: freebsd-python@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 427901350195 for <freebsd-python@mailman.ysv.freebsd.org>; Fri, 21 Dec 2018 16:52:45 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from mailman.ysv.freebsd.org (mailman.ysv.freebsd.org [IPv6:2001:1900:2254:206a::50:5]) by mx1.freebsd.org (Postfix) with ESMTP id D08CE729B9 for <freebsd-python@freebsd.org>; Fri, 21 Dec 2018 16:52:44 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: by mailman.ysv.freebsd.org (Postfix) id 942F11350192; Fri, 21 Dec 2018 16:52:44 +0000 (UTC) Delivered-To: python@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 71AE51350191 for <python@mailman.ysv.freebsd.org>; Fri, 21 Dec 2018 16:52:44 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from mxrelay.ysv.freebsd.org (mxrelay.ysv.freebsd.org [IPv6:2001:1900:2254:206a::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) server-signature RSA-PSS (4096 bits) client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.ysv.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 10392729B4 for <python@FreeBSD.org>; Fri, 21 Dec 2018 16:52:44 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2001:1900:2254:206a::16:76]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mxrelay.ysv.freebsd.org (Postfix) with ESMTPS id 3E18E16587 for <python@FreeBSD.org>; Fri, 21 Dec 2018 16:52:43 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org ([127.0.1.118]) by kenobi.freebsd.org (8.15.2/8.15.2) with ESMTP id wBLGqhuI028600 for <python@FreeBSD.org>; Fri, 21 Dec 2018 16:52:43 GMT (envelope-from bugzilla-noreply@freebsd.org) Received: (from www@localhost) by kenobi.freebsd.org (8.15.2/8.15.2/Submit) id wBLGqhlo028599 for python@FreeBSD.org; Fri, 21 Dec 2018 16:52:43 GMT (envelope-from bugzilla-noreply@freebsd.org) X-Authentication-Warning: kenobi.freebsd.org: www set sender to bugzilla-noreply@freebsd.org using -f From: bugzilla-noreply@freebsd.org To: python@FreeBSD.org Subject: [Bug 221700] lang/python??: subprocess does not use closefrom, calls close(2) hundreds of thousands of times Date: Fri, 21 Dec 2018 16:52:42 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Ports & Packages X-Bugzilla-Component: Individual Port(s) X-Bugzilla-Version: Latest X-Bugzilla-Keywords: needs-patch, performance X-Bugzilla-Severity: Affects Many People X-Bugzilla-Who: cem@freebsd.org X-Bugzilla-Status: Open X-Bugzilla-Resolution: X-Bugzilla-Priority: Normal X-Bugzilla-Assigned-To: emaste@freebsd.org X-Bugzilla-Flags: maintainer-feedback+ X-Bugzilla-Changed-Fields: Message-ID: <bug-221700-21822-1Y2MeMlBPp@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-221700-21822@https.bugs.freebsd.org/bugzilla/> References: <bug-221700-21822@https.bugs.freebsd.org/bugzilla/> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: freebsd-python@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: FreeBSD-specific Python issues <freebsd-python.freebsd.org> List-Unsubscribe: <https://lists.freebsd.org/mailman/options/freebsd-python>, <mailto:freebsd-python-request@freebsd.org?subject=unsubscribe> List-Archive: <http://lists.freebsd.org/pipermail/freebsd-python/> List-Post: <mailto:freebsd-python@freebsd.org> List-Help: <mailto:freebsd-python-request@freebsd.org?subject=help> List-Subscribe: <https://lists.freebsd.org/mailman/listinfo/freebsd-python>, <mailto:freebsd-python-request@freebsd.org?subject=subscribe> X-List-Received-Date: Fri, 21 Dec 2018 16:52:45 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D221700 --- Comment #13 from Conrad Meyer <cem@freebsd.org> --- (In reply to Ed Maste from comment #10) @Koobs (re: twitter), why would it not be async signal safe? In general signal safety is more about interacting with userspace memory st= ate of ordinary non-signal contexts given arbitrary signal interruption. I.e., classic example is stdio FILE objects, which may be locked or have corrupt, half-modified state. closefrom(2) is just a plain system call. The original commit, r194262, just says: > Note that this implementation of closefrom(2) does not make any effort to > resolve userland races with open(2) in other threads. As such, it is not > multithread safe. That is a comment on threading, not signals. Signaled, single-threaded programs are still single-threaded; the signal context and ordinary thread context do not run concurrently. And by definition, a user process cannot run code of any kind =E2=80=94 sig= nal-handler or ordinary =E2=80=94 while that user process is in the kernel. So closefr= om(2) in signal handler cannot race with open(2) or other syscalls that create fds in single-threaded programs. The scenario the comment refers to is something like this: - The program has two threads and fds 0-5 allocated. - Concurrently, thread A and B attempt to: A: open() a new fd B: closefrom(3) - The behavior is unpredictable and depends on which thread acquires the fdesctable lock first. [r194262]: https://svnweb.freebsd.org/base?view=3Drevision&revision=3D194262 --=20 You are receiving this mail because: You are on the CC list for the bug.=