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Wed, 25 Aug 2021 07:35:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=launchpad.net; s=20210803; t=1629876948; bh=Z5htvPo9C56L3NGnOGhhWSE97r4tYtuEimfVQmtBF5s=; h=MIME-Version:Content-Type:Date:From:To:Reply-To:References: Message-Id:Subject; b=ew0k4HIHReydHig0UTEVGs6REYPboXWJAQo85723t8uBM0s3ROPrBKTpeAhkNAhQg znUAYMgKkkyx6omXtN1aybT4aFgd4SeKguMjUALaY5LsjRRcbPVWIwyO4zw3k6mKm7 onNLQ3xppNW4d7cBotXKf3J2RS9md3Wk+xhG8oCCbXgiu/bJ53tdO1bbg+zv58alvM qKdwQWbFaKLggCwqZyUtIbonER1UGxzBMDrFp4Fj37v42dVNIgJIOrDsI9C4Po7dcs PcQvVJ8aYWdFAiGB68WzDU4YDijTPoZ+QGCJ5Ydsu5sGCG152s5y77tij0opu1QpYK 2HvS+6pUH70ng== Received: from loganberry.canonical.com (localhost [127.0.0.1]) by loganberry.canonical.com (Postfix) with ESMTP id DAF4C2E8138 for ; Wed, 25 Aug 2021 07:35:48 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Date: Wed, 25 Aug 2021 07:25:57 -0000 From: Thomas Huth <1585840@bugs.launchpad.net> To: qemu-devel@nongnu.org X-Launchpad-Notification-Type: bug X-Launchpad-Bug: product=qemu; status=Fix Released; importance=Undecided; assignee=None; X-Launchpad-Bug-Tags: linux-user X-Launchpad-Bug-Information-Type: Public X-Launchpad-Bug-Private: no X-Launchpad-Bug-Security-Vulnerability: no X-Launchpad-Bug-Commenters: jepler pmaydell th-huth X-Launchpad-Bug-Reporter: jepler (jepler) X-Launchpad-Bug-Modifier: Thomas Huth (th-huth) References: <20160526014921.26209.46866.malonedeb@chaenomeles.canonical.com> Message-Id: <162987635884.25887.15171074512074267282.launchpad@soybean.canonical.com> Subject: [Bug 1585840] Re: multiprocess program gets incorrect results with qemu arm-linux-user X-Launchpad-Message-Rationale: Subscriber (QEMU) @qemu-devel-ml X-Launchpad-Message-For: qemu-devel-ml Precedence: bulk X-Generated-By: Launchpad (canonical.com); Revision="7edb2d45353e030166106ae05838b77ab406edcd"; Instance="production" X-Launchpad-Hash: 36f7e04ffdb0b33537149463cab03e9eb02db6ce Received-SPF: pass client-ip=185.125.188.251; envelope-from=noreply@launchpad.net; helo=smtp-relay-services-1.canonical.com X-Spam_score_int: -42 X-Spam_score: -4.3 X-Spam_bar: ---- X-Spam_report: (-4.3 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Bug 1585840 <1585840@bugs.launchpad.net> Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" ** Changed in: qemu Status: Fix Committed =3D> Fix Released --=20 You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1585840 Title: multiprocess program gets incorrect results with qemu arm-linux-user Status in QEMU: Fix Released Bug description: The attached program can run either in a threaded mode or a multiprocess mode. It defaults to threaded mode, and switches to multiprocess mode if the first positional argument is "process". "success" of the test is defined as the final count being seen as 2000000 by both tasks. In standard linux x86_64 userspace (i7, 4 cores) and in standard armhf userspace (4 cores), the test program consistently completes successfully in both modes. But with qemu arm-linux-user, the test consistently succeeds in threaded mode and generally fails in multiprocess mode. The test reflects an essential aspect of how the Free and Open Source project linuxcnc's IPC system works: shared memory regions (created by shmat, but mmap would probably behave the same) contain data and mutexes. I observed that our testsuite encounters numerous deadlocks and failures when running in an schroot with qemu-user (x86_64 host), and I believe the underlying cause is improper support for atomic operations in a multiprocess model. (the testsuite consistently passes on real hardware) I observed the same failure at v1.6.0 and master (v2.6.0-424-g287db79), as well as in the outdated Debian version 1:2.1+dfsg-12+deb8u5a. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1585840/+subscriptions