From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from rock.gnat.com (rock.gnat.com [205.232.38.15]) by sourceware.org (Postfix) with ESMTP id 220373857C52; Tue, 5 Jan 2021 07:44:22 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 220373857C52 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=adacore.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=oliva@adacore.com Received: from localhost (localhost.localdomain [127.0.0.1]) by filtered-rock.gnat.com (Postfix) with ESMTP id CFB1E1166D7; Tue, 5 Jan 2021 02:44:21 -0500 (EST) X-Virus-Scanned: Debian amavisd-new at gnat.com Received: from rock.gnat.com ([127.0.0.1]) by localhost (rock.gnat.com [127.0.0.1]) (amavisd-new, port 10024) with LMTP id eGiofApTDnF2; Tue, 5 Jan 2021 02:44:21 -0500 (EST) Received: from free.home (tron.gnat.com [IPv6:2620:20:4000:0:46a8:42ff:fe0e:e294]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by rock.gnat.com (Postfix) with ESMTPS id 6D27811666A; Tue, 5 Jan 2021 02:44:21 -0500 (EST) Received: from livre (livre.home [172.31.160.2]) by free.home (8.15.2/8.15.2) with ESMTPS id 1057iDd7407057 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 5 Jan 2021 04:44:14 -0300 From: Alexandre Oliva To: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org Subject: calibrate intervals to avoid zero in futures poll test Organization: Free thinker, does not speak for AdaCore Errors-To: aoliva@lxoliva.fsfla.org Date: Tue, 05 Jan 2021 04:44:13 -0300 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.84 X-Spam-Status: No, score=-11.9 required=5.0 tests=BAYES_00, GIT_PATCH_0, KAM_DMARC_STATUS, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 05 Jan 2021 07:44:23 -0000 We get occasional failures of 30_threads/future/members/poll.cc on some platforms whose high resolution clock doesn't have such a high resolution; wait_for_0 ends up as 0, and then some asserts fail as intervals measured as longer than zero are tested for less than several times zero. This patch adds some calibration in the iteration count to set a measurable base time interval with some additional margin. Regstrapped on x86_64-linux-gnu, and also tested on x-arm-wrs-vxworks7r2. Ok to install? for libstdc++-v3/ChangeLog * testsuite/30_threads/future/members/poll.cc: Calibrate iteration count. --- .../testsuite/30_threads/future/members/poll.cc | 33 +++++++++++++++++++- 1 file changed, 32 insertions(+), 1 deletion(-) diff --git a/libstdc++-v3/testsuite/30_threads/future/members/poll.cc b/libstdc++-v3/testsuite/30_threads/future/members/poll.cc index fff9bea899c90..7b41411a54386 100644 --- a/libstdc++-v3/testsuite/30_threads/future/members/poll.cc +++ b/libstdc++-v3/testsuite/30_threads/future/members/poll.cc @@ -25,7 +25,7 @@ #include #include -const int iterations = 200; +int iterations = 200; using namespace std; @@ -45,10 +45,41 @@ int main() promise p; future f = p.get_future(); + start_over: auto start = chrono::high_resolution_clock::now(); for(int i = 0; i < iterations; i++) f.wait_for(chrono::seconds(0)); auto stop = chrono::high_resolution_clock::now(); + + /* We've run too few iterations for the clock resolution. + Attempt to calibrate it. */ + if (start == stop) + { + /* Loop until the clock advances, so that start is right after a + time increment. */ + do + start = chrono::high_resolution_clock::now(); + while (start == stop); + int i = 0; + /* Now until the clock advances again, so that stop is right + after another time increment. */ + do + { + f.wait_for(chrono::seconds(0)); + stop = chrono::high_resolution_clock::now(); + i++; + } + while (start == stop); + /* Got for some 10 cycles, but we're already past that and still + get into the calibration loop, double the iteration count and + try again. */ + if (iterations < i * 10) + iterations = i * 10; + else + iterations *= 2; + goto start_over; + } + double wait_for_0 = print("wait_for(0s)", stop - start); start = chrono::high_resolution_clock::now(); -- Alexandre Oliva, happy hacker https://FSFLA.org/blogs/lxo/ Free Software Activist GNU Toolchain Engineer Vim, Vi, Voltei pro Emacs -- GNUlius Caesar