From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Koehrer Mathias (ETAS/ESW5)" Subject: Kernel 4.9.x-rt Fully Preemptible Kernel: Issue with gdb and unexpected SIGSTOP signals Date: Mon, 23 Jan 2017 13:43:22 +0000 Message-ID: <6bec5da671344b7e862ee74dafacb3b5@FE-MBX1012.de.bosch.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT To: linux-rt-users Return-path: Received: from smtp6-v.fe.bosch.de ([139.15.237.11]:52503 "EHLO smtp6-v.fe.bosch.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750718AbdAWNn0 (ORCPT ); Mon, 23 Jan 2017 08:43:26 -0500 Received: from vsmta12.fe.internet.bosch.com (unknown [10.4.98.52]) by imta24.fe.bosch.de (Postfix) with ESMTP id 2357ED8022A for ; Mon, 23 Jan 2017 14:43:24 +0100 (CET) Received: from FE-MBX1011.de.bosch.com (vsgw22.fe.internet.bosch.com [10.4.98.11]) by vsmta12.fe.internet.bosch.com (Postfix) with ESMTP id 016B41B80E97 for ; Mon, 23 Jan 2017 14:43:24 +0100 (CET) Content-Language: de-DE Sender: linux-rt-users-owner@vger.kernel.org List-ID: Hi all, with the 4.9.0-rt1 and also the 4.9.4-rt2 kernel (x86, 64bit) I observe a strange issue when running my multithreaded real time executable within gdb. Fairly often (in about 40% of all runs) the gdb stops executing with the message: Thread 8 "MDL07-Acknowled" received signal SIGSTOP, Stopped (signal). [Switching to Thread 0x7fffef141700 (LWP 9770)] 0x00007ffff535b24d in read () at ../sysdeps/unix/syscall-template.S:84 Often it helps to enter "continue" a couple of times to continue the debugging. However, sometimes it ends up in an endless loop of "continue" followed by a SIGSTOP, "continue", etc. If this issue occurs, the SIGSTOP is complained for all threads in the executable. Different system calls are affected: read, select, pselect, clone (via pthread_create), ... Debugging is more or less impossible due to this issue. No SIGSTOP is sent out by the application, the root cause for this signal is not clear to me. When I reconfigured the kernel to use "Preemptible Kernel (Basic RT)" I do not observer this issue. Also with kernel 3.18.42-rt44 (Fully Preemptible) it works fine. I never see this issue there. Any hints on how to solve the issue are highly appreciated. Thanks Best regards Mathias