From nobody Fri Nov 29 14:47:28 2024 Received: from mail-pf1-f201.google.com (mail-pf1-f201.google.com [209.85.210.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 20C301494B1 for ; Wed, 18 Sep 2024 23:11:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726701068; cv=none; b=HOc/kyzlGedtzXtD3C4oKzbnYrFPf8mU+d2na5CdMXhWCy726pTffrUB+pzbXXZVLKjHy/+Qyz1NCVWmtNuLnALURJwW4dzZ45w+2pJAUeRV8trisJOF4gD0zf6m4ZGskZn8YvWzdJroLGe1MKGa+QF6QECYzpFf+y4gyio0Yuk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726701068; c=relaxed/simple; bh=jEpaRqX8x9ZoV7NGwJBcnn25L7osKDYWpdYayHxA/LA=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=lfgLDEJVteosDDRy63C47EJFtGc3xwF1Oy2Xe9ZLAGBchZ1FCKPKFsJFt75jnKptoX6aFyBZZvo4Ac/VRpNkJI5Qr1ONtjtWqfgKLNYUEkgU+HU9/mmOarNghdvVXDaF3nLwLFsLKtOBpq4EgmGGPhgrpfWuokz/IxvOtTeJSAo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--edliaw.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=MJrtMhw5; arc=none smtp.client-ip=209.85.210.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--edliaw.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="MJrtMhw5" Received: by mail-pf1-f201.google.com with SMTP id d2e1a72fcca58-718f329aefdso302218b3a.1 for ; Wed, 18 Sep 2024 16:11:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1726701066; x=1727305866; darn=vger.kernel.org; h=content-transfer-encoding:cc:to:from:subject:message-id :mime-version:date:from:to:cc:subject:date:message-id:reply-to; bh=YA0w8JE4YsZuKs1FGvLh6dGW1GjJTJ/xAnovafRZBSc=; b=MJrtMhw54XtXOyZ8tRGDSBIYxlM/yUJ+d434GC19k3RiKsGUs3FpPuXQ85ctsrlEJh ZpHPAI9wamm4FR7hg734OGaVcdZrzNZU3FYtQM3FAsf7UseBPNr24ghtrm3rlX50W8Bp 316jaG10wdkpb80sBRnCO/dOMxONDcPUyLxw6eB7w0ZIUyQlNk3TPockQ34yk3dFHej9 6B3/j5eaNHwlQkuYhaVlk86fvGBHEnV7U/JZuvpkpgH2m1YAAIQTKTnTPFTbqx5z9gLB 2HjyDm7o8jkwjPkzMt3N1k2a5NUEtzOPLEurbK9qEp7QGEFCpEAC1SEF+O83w9gu5AWs bVRQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1726701066; x=1727305866; h=content-transfer-encoding:cc:to:from:subject:message-id :mime-version:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=YA0w8JE4YsZuKs1FGvLh6dGW1GjJTJ/xAnovafRZBSc=; b=COwdylveSfC30UTlqH3exhliNNyznx1TC7czUbgQwzSYpMZJybWz+0snoiWZ0raYT7 TEmZJvInLNR8+G7YgDIch5ka1dUzBkOg/oB+LD9Ed79cypyouUC1F+QJtB4sxtmJm21U kZy/vK4QBQZ8cxxepy/saByR7v2Qp6BFbYRI+XyohWRg91liqknHggy/MxP0Otpwh/Xp 6m+pB23I0u9EcwFVICYQN8QTDJu/zO4bw6U3s9TfP+1rglKHmvylFu+lK9WxKyUeKRXd yDXGeIrvpdVUqIjPpmIVOrNT3TfC+MSxGbXrUvswBEbw3eqAYqedCl1N8kzZdmwi7ES9 SoqA== X-Gm-Message-State: AOJu0YxLMw6L4HyKZADHbNr7V+PXwXyNn+akI1WyIx0jvlH3ihGpbK4Y 3Yl2E0naAh9yWYuVToqGTp0P0IXGoktCw9gAymbrHK8HTTAukrz8hiG3YinZYK039loHomcRu8E 1/Q== X-Google-Smtp-Source: AGHT+IFR5wvpsM8KmOcWHfEpfCZTMacE04uaSHilS6oprIqygqchRKXw74pEjG1MSWi2VY6unf7hnOt+cOo= X-Received: from edliaw.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:305d]) (user=edliaw job=sendgmr) by 2002:a62:e302:0:b0:718:d4f5:aa40 with SMTP id d2e1a72fcca58-71936b74189mr42304b3a.5.1726701065978; Wed, 18 Sep 2024 16:11:05 -0700 (PDT) Date: Wed, 18 Sep 2024 23:11:00 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.46.0.662.g92d0881bb0-goog Message-ID: <20240918231102.234253-1-edliaw@google.com> Subject: [PATCH RESEND v2] selftests/futex: Order calls in futex_requeue From: Edward Liaw To: linux-kselftest@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Peter Zijlstra , Darren Hart , Davidlohr Bueso , "=?UTF-8?q?Andr=C3=A9=20Almeida?=" , Shuah Khan , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , "H. Peter Anvin" , Andy Lutomirski Cc: linux-kernel@vger.kernel.org, kernel-team@android.com, Edward Liaw , Muhammad Usama Anjum , Davidlohr Bueso , llvm@lists.linux.dev Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Fixes a race between parent and child threads in futex_requeue. Similar to fbf4dec70277 ("selftests/futex: Order calls to futex_lock_pi"), which fixed a flake in futex_lock_pi due to racing between the parent and child threads. The same issue can occur in the futex_requeue test, because it expects waiterfn to make progress to futex_wait before the parent starts to requeue. This is mitigated by the parent sleeping for WAKE_WAIT_US, but it still fails occasionally. This can be reproduced by adding a sleep in the waiterfn before futex_wait: TAP version 13 1..2 not ok 1 futex_requeue simple returned: 0 not ok 2 futex_requeue simple returned: 0 not ok 3 futex_requeue many returned: 0 not ok 4 futex_requeue many returned: 0 Instead, replace the sleep with barriers to make the sequencing explicit. Fixes: 7cb5dd8e2c8c ("selftests: futex: Add futex compare requeue test") Signed-off-by: Edward Liaw Reviewed-by: Muhammad Usama Anjum Reviewed-by: Andr=C3=A9 Almeida --- .../selftests/futex/functional/futex_requeue.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/tools/testing/selftests/futex/functional/futex_requeue.c b/too= ls/testing/selftests/futex/functional/futex_requeue.c index 51485be6eb2f..8f7d3e8bf32a 100644 --- a/tools/testing/selftests/futex/functional/futex_requeue.c +++ b/tools/testing/selftests/futex/functional/futex_requeue.c @@ -12,9 +12,9 @@ #define TEST_NAME "futex-requeue" #define timeout_ns 30000000 -#define WAKE_WAIT_US 10000 volatile futex_t *f1; +static pthread_barrier_t barrier; void usage(char *prog) { @@ -32,6 +32,8 @@ void *waiterfn(void *arg) to.tv_sec =3D 0; to.tv_nsec =3D timeout_ns; + pthread_barrier_wait(&barrier); + if (futex_wait(f1, *f1, &to, 0)) printf("waiter failed errno %d\n", errno); @@ -70,13 +72,15 @@ int main(int argc, char *argv[]) ksft_print_msg("%s: Test futex_requeue\n", basename(argv[0])); + pthread_barrier_init(&barrier, NULL, 2); /* * Requeue a waiter from f1 to f2, and wake f2. */ if (pthread_create(&waiter[0], NULL, waiterfn, NULL)) error("pthread_create failed\n", errno); - usleep(WAKE_WAIT_US); + pthread_barrier_wait(&barrier); + pthread_barrier_destroy(&barrier); info("Requeuing 1 futex from f1 to f2\n"); res =3D futex_cmp_requeue(f1, 0, &f2, 0, 1, 0); @@ -99,6 +103,7 @@ int main(int argc, char *argv[]) ksft_test_result_pass("futex_requeue simple succeeds\n"); } + pthread_barrier_init(&barrier, NULL, 11); /* * Create 10 waiters at f1. At futex_requeue, wake 3 and requeue 7. @@ -109,7 +114,8 @@ int main(int argc, char *argv[]) error("pthread_create failed\n", errno); } - usleep(WAKE_WAIT_US); + pthread_barrier_wait(&barrier); + pthread_barrier_destroy(&barrier); info("Waking 3 futexes at f1 and requeuing 7 futexes from f1 to f2\n"); res =3D futex_cmp_requeue(f1, 0, &f2, 3, 7, 0); -- 2.46.0.662.g92d0881bb0-goog