From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AB711C04EBF for ; Wed, 5 Dec 2018 17:56:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7E121213A2 for ; Wed, 5 Dec 2018 17:56:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7E121213A2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727872AbeLER4t (ORCPT ); Wed, 5 Dec 2018 12:56:49 -0500 Received: from mx1.redhat.com ([209.132.183.28]:39998 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727297AbeLER4s (ORCPT ); Wed, 5 Dec 2018 12:56:48 -0500 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 837DA1E32B; Wed, 5 Dec 2018 17:56:48 +0000 (UTC) Received: from krava (unknown [10.43.17.30]) by smtp.corp.redhat.com (Postfix) with SMTP id 25BC82AAA2; Wed, 5 Dec 2018 17:56:38 +0000 (UTC) Date: Wed, 5 Dec 2018 18:56:38 +0100 From: Jiri Olsa To: Steven Rostedt Cc: Jiri Olsa , Arnaldo Carvalho de Melo , Peter Zijlstra , lkml , Ingo Molnar , Namhyung Kim , Alexander Shishkin , Thomas Gleixner , "Luis Claudio R. Goncalves" , ldv@altlinux.org, esyr@redhat.com, Frederic Weisbecker Subject: Re: [PATCH 1/8] perf: Allow to block process in syscall tracepoints Message-ID: <20181205175638.GD3836@krava> References: <20181205160509.1168-1-jolsa@kernel.org> <20181205160509.1168-2-jolsa@kernel.org> <20181205123503.4b8e0484@vmware.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181205123503.4b8e0484@vmware.local.home> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Wed, 05 Dec 2018 17:56:48 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 05, 2018 at 12:35:03PM -0500, Steven Rostedt wrote: > On Wed, 5 Dec 2018 17:05:02 +0100 > Jiri Olsa wrote: > > > diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c > > index 3b2490b81918..e55cf9169a03 100644 > > --- a/arch/x86/entry/common.c > > +++ b/arch/x86/entry/common.c > > @@ -60,6 +60,32 @@ static void do_audit_syscall_entry(struct pt_regs *regs, u32 arch) > > } > > } > > > > +static void trace_block_syscall(struct pt_regs *regs, bool enter) > > +{ > > + current->perf_blocked = true; > > + > > + do { > > + schedule_timeout(100 * HZ); > > + current->perf_blocked_cnt = 0; > > + > > + if (enter) { > > + /* perf syscalls:* enter */ > > + perf_trace_syscall_enter(regs); > > + > > + /* perf raw_syscalls:* enter */ > > + perf_trace_sys_enter(&event_sys_enter, regs, regs->orig_ax); > > + } else { > > + /* perf syscalls:* enter */ > > + perf_trace_syscall_exit(regs); > > + > > + /* perf raw_syscalls:* enter */ > > + perf_trace_sys_exit(&event_sys_exit, regs, regs->ax); > > + } > > + } while (current->perf_blocked_cnt); > > I was thinking, if the process reading the perf buffer dies, how do we > tell this task to continue on? when the tracer process dies, its event will get uninstalled from the trace_event_call::perf_events list, so the next iteration of above loop won't get any blocked event and it will leave (assuming there's just single event) jirka