From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: linux-rt-users-owner@vger.kernel.org Received: from afk.unpythonic.net ([138.68.55.246]:38902 "EHLO afk.unpythonic.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725787AbeJXGkX (ORCPT ); Wed, 24 Oct 2018 02:40:23 -0400 Date: Tue, 23 Oct 2018 16:48:12 -0500 From: Jeff Epler Subject: Re: system() instruction creates latency peaks Message-ID: <20181023214812.3sqxq7w7xtnh6b2h@unpythonic.net> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-rt-users-owner@vger.kernel.org List-ID: To: verrodj@uymail.com Cc: linux-rt-users@vger.kernel.org Hi, I have experienced similar symptoms in realtime programs (LinuxCNC). We have a control thread which sometimes does operations like system(), and one or more realtime threads. There, we changed from using system() to using posix_spawn and it appears to have resolved the problem. However, I don't have any explanation as to why this is the case. On the specific version of glibc I have, posix_spawn uses vfork and system uses clone; other syscalls like rt_sigaction are taken in the system case but not the posix_spawn case. Jeff