From owner-freebsd-bugs@freebsd.org Mon Feb 11 05:46:15 2019 Return-Path: Delivered-To: freebsd-bugs@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 D751E14E9A25 for ; Mon, 11 Feb 2019 05:46:14 +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 6C36684D2D for ; Mon, 11 Feb 2019 05:46:14 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: by mailman.ysv.freebsd.org (Postfix) id 29CF914E9A24; Mon, 11 Feb 2019 05:46:14 +0000 (UTC) Delivered-To: bugs@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 0231F14E9A23 for ; Mon, 11 Feb 2019 05:46:14 +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 8C4F384D2C for ; Mon, 11 Feb 2019 05:46:13 +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 C19FD1AD5C for ; Mon, 11 Feb 2019 05:46:12 +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 x1B5kCsE089475 for ; Mon, 11 Feb 2019 05:46:12 GMT (envelope-from bugzilla-noreply@freebsd.org) Received: (from www@localhost) by kenobi.freebsd.org (8.15.2/8.15.2/Submit) id x1B5kCbv089474 for bugs@FreeBSD.org; Mon, 11 Feb 2019 05:46:12 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: bugs@FreeBSD.org Subject: [Bug 235657] /usr/libexec/atrun race causes missed jobs Date: Mon, 11 Feb 2019 05:46:11 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: bin X-Bugzilla-Version: 12.0-STABLE X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Some People X-Bugzilla-Who: karl@denninger.net X-Bugzilla-Status: New X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: bugs@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_id short_desc product version rep_platform op_sys bug_status bug_severity priority component assigned_to reporter attachments.created Message-ID: 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-bugs@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Bug reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 11 Feb 2019 05:46:15 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D235657 Bug ID: 235657 Summary: /usr/libexec/atrun race causes missed jobs Product: Base System Version: 12.0-STABLE Hardware: Any OS: Any Status: New Severity: Affects Some People Priority: --- Component: bin Assignee: bugs@FreeBSD.org Reporter: karl@denninger.net Created attachment 201915 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=3D201915&action= =3Dedit Diff against /usr/src/libexec/atrun directory I have no idea why this hasn't bit people before, or isn't biting people now.... but it is biting me. /usr/libexec/atrun is the "batch" job executor out of the cron and by defau= lt runs every 5 minutes. The code has an unlink call in it that attempts to remove old jobs from the queue but unfortunately the queue code can select a job to run, call fork()= to start it, post-fork() the child can give up the CPU before it opens the file containing the job and thus the queue code (which is in the parent) can exe= cute the unlink before the child process gets the file open. If this happens you get a "file not found" error in the cron log and the job doesn't run. The attached patch fixes the potential race by moving the unlink into the child; it may not be the most-elegant, but it works. Unfortunately due to = the code's structure (it performs multiple tests on the file to be run for secu= rity reasons) there are multiple error exits and, in the event of any of those, = you must unlink the file as well or it will try to run repeatedly -- yet you ca= n't unlink it immediately after it is opened because some of the tests require = it still be on the filesystem. --=20 You are receiving this mail because: You are the assignee for the bug.=