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=-4.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS autolearn=no 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 82DAAC433E0 for ; Wed, 20 May 2020 15:47:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 409D02070A for ; Wed, 20 May 2020 15:47:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589989628; bh=RVEMDBCL04OQbznOldT6yF83HEYpiWi2l9Yt3I18qsg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=xohh15ukwlEDMJfVGh+bpcTjiZe8w4k/80EPobz1+JeD8mEcEuOK4AXWEz5jHL+yU iN3D2r+SV7s4SX30aSEeXuNwj7Bujerad//FePG4pusu0d9FYbrLFSQg6zO0iDAPEq YLyBVFghOGNSehB++snKlv+8XO81jL3ETv9wS7bM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726840AbgETPrH (ORCPT ); Wed, 20 May 2020 11:47:07 -0400 Received: from mail.kernel.org ([198.145.29.99]:36498 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726691AbgETPrH (ORCPT ); Wed, 20 May 2020 11:47:07 -0400 Received: from quaco.ghostprotocols.net (unknown [179.97.37.151]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 6475B20709; Wed, 20 May 2020 15:47:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589989626; bh=RVEMDBCL04OQbznOldT6yF83HEYpiWi2l9Yt3I18qsg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=s80+r20fIdm93fdte+1ohs1iI2BcmvV8lU7OlyjUdKYXjiei3d/nA/GKeWKRHX/fn NQq13l+KZplmz5yTVPqQFEkFKgZpU8UrQp4MttuKQcU9m1S4nKNhxhJ7RURQMs2KQ3 ZWecSKBFX6UjyVd1wozIvKPGemuRC2zzWH8NWDD8= Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id 50B9C40AFD; Wed, 20 May 2020 12:47:04 -0300 (-03) Date: Wed, 20 May 2020 12:47:04 -0300 From: Arnaldo Carvalho de Melo To: Jiri Olsa Cc: Anand K Mistry , linux-perf-users@vger.kernel.org, Alexander Shishkin , Ingo Molnar , Mark Rutland , Namhyung Kim , Peter Zijlstra , linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] perf record: Use an eventfd to wakeup when done Message-ID: <20200520154704.GL32678@kernel.org> References: <20200508145624.1.I4d7421c6bbb1f83ea58419082481082e19097841@changeid> <20200513122012.v3.1.I4d7421c6bbb1f83ea58419082481082e19097841@changeid> <20200513113941.GK3158213@krava> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200513113941.GK3158213@krava> X-Url: http://acmel.wordpress.com Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Wed, May 13, 2020 at 01:39:41PM +0200, Jiri Olsa escreveu: > On Wed, May 13, 2020 at 12:20:23PM +1000, Anand K Mistry wrote: > > The setting and checking of 'done' contains a rare race where the signal > > handler setting 'done' is run after checking to break the loop, but > > before waiting in evlist__poll(). In this case, the main loop won't wake > > up until either another signal is sent, or the perf data fd causes a > > wake up. > > > > The following simple script can trigger this condition (but you might > > need to run it for several hours): > > for ((i = 0; i >= 0; i++)) ; do > > echo "Loop $i" > > delay=$(echo "scale=4; 0.1 * $RANDOM/32768" | bc) > > ./perf record -- sleep 30000000 >/dev/null& > > pid=$! > > sleep $delay > > kill -TERM $pid > > echo "PID $pid" > > wait $pid > > done > > > > At some point, the loop will stall. Adding logging, even though perf has > > received the SIGTERM and set 'done = 1', perf will remain sleeping until > > a second signal is sent. > > > > Signed-off-by: Anand K Mistry > > > > --- > > > > Changes in v3: > > - Move done_fd creation to below session initialisation > > - Close done_fd on exit > > - Log errno when write(done_fd) fails > > Acked-by: Jiri Olsa I've made this dependent on HAVE_EVENTFD_SUPPORT, so that it continues building on older systems, - Arnaldo