From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 2140) id 335683858D28; Fri, 3 Mar 2023 20:14:19 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 335683858D28 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1677874459; bh=I2KpUfGLBibj/RGJV+Pkgpw+ft+tZD6GKHocw6JZUiU=; h=From:To:Subject:Date:From; b=bywHG/4KNiDvQhnFvHIcLt8FC8dkYFquwWs1AvqUDML0hwoXLjyVfdt+hQ7v5kI59 2TfwFs33xxwbS32H9zmvo2yXT50eZBSZQ7LMFmls48RVUMW6pSQKOh1jniE3/ZEl7t lPsZWvt7khMTQ3Zhbqoyvp7aXm3cmhmbqBau7Dt8= MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" From: Alexandre Oliva To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r13-6464] libstdc++: testsuite: async.cc early timeout X-Act-Checkin: gcc X-Git-Author: Alexandre Oliva X-Git-Refname: refs/heads/master X-Git-Oldrev: 1f83aee5864129c4147a95c1a4e35d37c7eb7e59 X-Git-Newrev: 16554ba1fe66a09f99adde1220a2cd4f7e5e2d64 Message-Id: <20230303201419.335683858D28@sourceware.org> Date: Fri, 3 Mar 2023 20:14:19 +0000 (GMT) List-Id: https://gcc.gnu.org/g:16554ba1fe66a09f99adde1220a2cd4f7e5e2d64 commit r13-6464-g16554ba1fe66a09f99adde1220a2cd4f7e5e2d64 Author: Alexandre Oliva Date: Wed May 4 23:41:38 2022 -0300 libstdc++: testsuite: async.cc early timeout The async call and future variable initialization may take a while to complete on uniprocessors, especially if the async call and other unrelated processes run before context switches back to the main thread. Taking steady_begin only then sometimes causes the 11*100ms in the slow clock, counted from before the async call, to not be enough for the measured wait to last 1s in the steady clock. I've seen it fall short of 1s by as little as a third of a tenth of a second in some cases, but in one surprisingly extreme case the elapsed wait time got only up to 216.7ms. Initializing both timestamps next to each other, before the async call, appears to avoid the problem entirely. I've renamed the variable moved out of the block so as to avoid name hiding in the subsequent block, that has another steady_begin variable. The second wait fails a lot less frequently, but the 2s limit has been exceeded, so I'm bumping up the max sleep to ~4s, and the tolerance to 3s. for libstdc++-v3/ChangeLog * testsuite/30_threads/async/async.cc (test04): Initialize steady_start, renamed from steady_begin, next to slow_start. Increase tolerance for final wait. Diff: --- libstdc++-v3/testsuite/30_threads/async/async.cc | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/libstdc++-v3/testsuite/30_threads/async/async.cc b/libstdc++-v3/testsuite/30_threads/async/async.cc index 2687e92ee40..4e290e581c2 100644 --- a/libstdc++-v3/testsuite/30_threads/async/async.cc +++ b/libstdc++-v3/testsuite/30_threads/async/async.cc @@ -20,6 +20,7 @@ // with this library; see the file COPYING3. If not see // . +#include #include #include @@ -133,6 +134,7 @@ void test04() { using namespace std::chrono; + auto const steady_start = steady_clock::now(); auto const slow_start = slow_clock::now(); future f1 = async(launch::async, []() { std::this_thread::sleep_for(std::chrono::seconds(2)); @@ -140,21 +142,26 @@ void test04() // Wait for ~1s { - auto const steady_begin = steady_clock::now(); auto const status = f1.wait_until(slow_start + milliseconds(100)); VERIFY(status == std::future_status::timeout); - auto const elapsed = steady_clock::now() - steady_begin; + auto const elapsed = steady_clock::now() - steady_start; + if (elapsed < seconds(1)) + std::cout << elapsed.count () << "ns < 1s" << std::endl; VERIFY(elapsed >= seconds(1)); VERIFY(elapsed < seconds(2)); } - // Wait for up to ~2s more + // Wait for up to ~4s more, but since the async sleep completes, the + // actual wait may be shorter than 1s. Tolerate 3s because 2s + // hasn't been enough in some extreme cases. { auto const steady_begin = steady_clock::now(); - auto const status = f1.wait_until(slow_start + milliseconds(300)); + auto const status = f1.wait_until(slow_start + milliseconds(500)); VERIFY(status == std::future_status::ready); auto const elapsed = steady_clock::now() - steady_begin; - VERIFY(elapsed < seconds(2)); + if (elapsed >= seconds(3)) + std::cout << elapsed.count () << "ns > 2s" << std::endl; + VERIFY(elapsed < seconds(3)); } }