From owner-freebsd-testing@freebsd.org Wed Apr 26 02:22:55 2017 Return-Path: Delivered-To: freebsd-testing@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 7CDC4D4FCB3; Wed, 26 Apr 2017 02:22:55 +0000 (UTC) (envelope-from yaneurabeya@gmail.com) Received: from mail-qk0-x232.google.com (mail-qk0-x232.google.com [IPv6:2607:f8b0:400d:c09::232]) (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 3EF8EA49; Wed, 26 Apr 2017 02:22:55 +0000 (UTC) (envelope-from yaneurabeya@gmail.com) Received: by mail-qk0-x232.google.com with SMTP id f76so81246756qke.2; Tue, 25 Apr 2017 19:22:55 -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=+cf7DkfaPGHK/kZGSh4y+qCLx/Juvh2LAkdfUwudXfA=; b=dsnPJYgd1wdKa/olZOJEvon/YuzMXAce1KHuUx8+iF6HfYWvw7dtGgtphv7ZUQyGug VUSqXs0Igll3clIQrEQ3SUuwC+xEOjhx2EaRmWVj6yEyx9rJR+KqOhtYQkx2RhukxRZN GhNb4yCYeu/ltVIkI19H1Cb5+mXkgyd/hUP5g9gizWg0GgrLZlLFddxRCW0wNdONr9D/ DgEvgcSBrcABAxv4XQGMy+WMWBnNk53f4slkIBn6pJvU7qdb4A9m2ae/P7J7YQV1YnCB Tfs5gBBa6smz/PkDaNELHc1iBUQWJmdOccydJBN4J9ZdQHEi8VkKtum0dycsRswoUnKL SAnA== 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=+cf7DkfaPGHK/kZGSh4y+qCLx/Juvh2LAkdfUwudXfA=; b=NI6YIwjPKSLzEocOdU0vDwJUU0ZfL1PmIl9nEBeXHhESQ4N6tfS0ToxB1PBJiRbFfB veZzDbZUxAiIXtKBeYu45/KdN15aAJ0+NqVfrPkRI10ra8Tzrvg4pH58vCBg+UTd/IEl wRSF6rTi9FGS/BK53q2KQ3Bjm8WYXGYSOs6p9zUmjk/Ql5QZsW6KG9Vq7iADbiMLObor BjYp8zDR6BRqZUOOxx7Rs63o6TvMr4mM6cupCaHa/4MvojgGC9eE2St0daf8Ajnz5WTg EXWauDTNf/G9pifa+QubZK0hi1DNWJGDywDOWkIqNtVJm891Nlv9E9etdMRT94jvKGPv aHSg== X-Gm-Message-State: AN3rC/5wlSbANhOrcZp4yfoFptEFM6F6enGRdChQRyx7Buu2Klnm6HrC RjvEsY9mVEz1WUVev1PExewx0mexXmll X-Received: by 10.55.127.199 with SMTP id a190mr21761429qkd.123.1493173374248; Tue, 25 Apr 2017 19:22:54 -0700 (PDT) MIME-Version: 1.0 Received: by 10.140.93.83 with HTTP; Tue, 25 Apr 2017 19:22:53 -0700 (PDT) In-Reply-To: <20170425230247.GA8201@spindle.one-eyed-alien.net> References: <20170425230247.GA8201@spindle.one-eyed-alien.net> From: Ngie Cooper Date: Tue, 25 Apr 2017 19:22:53 -0700 Message-ID: Subject: Re: racy tests To: Brooks Davis Cc: "freebsd-hackers@freebsd.org" , Alan Somers , "bdrewery@freebsd.org" , "freebsd-testing@freebsd.org" Content-Type: text/plain; charset=UTF-8 X-BeenThere: freebsd-testing@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Testing on FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 26 Apr 2017 02:22:55 -0000 On Tue, Apr 25, 2017 at 4:02 PM, Brooks Davis wrote: > I've been running the FreeBSD test suite for mips64 under qemu. As a > result, I'm seeing some tests fail due to assumptions about timing producing > test races. For example one of the pwait tests does this: > > timeout_many_body() > { > sleep 1 & > p1=$! > > sleep 5 & > p5=$! > > sleep 10 & > p10=$! > > atf_check \ > -o empty \ > -e empty \ > -s exit:124 \ > timeout --preserve-status 7.5 pwait -t 6 $p1 $p5 $p10 > } > > Under emulation, particularly if the host disks are busy, it's easily > possible for the first sleep to exit before pwait actually runs. > In practice, we could probably get away with cranking up the times a > fair bit, but that would make the test slow and the race would still > exist. > > Any thoughts about the right solution? Something not time based would > be ideal, but then it seems like we'd need a parallel process to kill > some of the waited for victims we quickly end up with something more > complicated than pwait that also needs testing... (Adding bdrewery@, testing@) I need to think about this a bit. The issue might be that we're using the wrong timer for sleep(1)/need to account for being interrupted. Needless to say, emulation really screws up timing assumptions because virtual clocks don't function like hardware clocks. Thanks, -Ngie