From nobody Sun Feb 8 05:03:30 2026 Received: from mail-yw1-f201.google.com (mail-yw1-f201.google.com [209.85.128.201]) (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 D15AD1D223A for ; Tue, 3 Sep 2024 20:40:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725396015; cv=none; b=YiZGO1ua6cjMrt8NIqe3pnLPiwVj6RZ0U8RAR+7aLWLqYPWFmVdFH5QJOT+x5OpGgDjW9tpo4TTtmDduBWjWTdvt2f6UvdR9ZejEEo018gJu44idQkM3T8HCcbodEOzEX4TmGG6GNmWSwUsB4oREYQYUNzg3a8tLQRJ47nvKym4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725396015; c=relaxed/simple; bh=cCmLjf308k6OsUJLrInpoUdAeJs7fWLaNbFSDImA684=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=pfxuq/Tl83IofHNlgcNmCIwb/tc973F/4reHD7GR37Ewu9dkudYwNxWW+OYJ41qa/ayO/EhWMVzEns5Ey3C2oPqVcrqSflJA414qhDCbvCcOKr1dG0CT7njSEhnlpA+nArxsRJNuChl4kxehLtiJrT7VOU24SfHJYqLJ7YWp/S0= 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=cXlMWqtN; arc=none smtp.client-ip=209.85.128.201 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="cXlMWqtN" Received: by mail-yw1-f201.google.com with SMTP id 00721157ae682-6b47ff8a5c4so111015497b3.2 for ; Tue, 03 Sep 2024 13:40:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1725396013; x=1726000813; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=gr0+wD1hQSkgsAJy15LgXOqT17mmHStoYkWLI3kOh1E=; b=cXlMWqtNbG9zhOlXPMihLtpr5nhe4BzDkxU9LdrLlY1lJCr5OIn0+6jSm8HZYY0422 Br8c7ZwVzdtkU5vc7xEMh+Uh3naN2azLlpctk0/S4hwGt4Ut65eRRds71TI5BXPDi6ea 3xD8Mo86RI6INjS0rO/lIO39LC3qV6iWyRMHlhzxhQ0Hz+LvpJXKMytpZEPMf3gFn+TH lyhBgfRDmDieONFeHqF8G4purijtXERbF6JprBf+nfcK4KxSYUwp66JR0mPrQ1lD+b// 35o9b355/bl34igrZgd3sfVVgW5v5dmERdrjO2hVyj2b8O9jJQtHLMw9gJ7q1uiBkiSv W55Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1725396013; x=1726000813; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=gr0+wD1hQSkgsAJy15LgXOqT17mmHStoYkWLI3kOh1E=; b=tm6k5/NJFW4xDsJ9LpbpHTqkpW03DmuTZq6YbT+q8EyGkkd5bmeUibgAO5ycqFvYeB Vz0xW0qvcU6JpNa/EV+s0hBvPYk9F7VPO9Zw0MX84sxCNW+/m8LrA4i6NlW4ICli9FUK 1QR3RNtJaYAaMLOT5aIPAVm5c9aWcME7rUlfYiSTeHadi9aSoAk2Zx6NZ4tqiqcfAcwp IHILJgoXjag1m+0Dn7n83lFT4lW7nySbuBURM4S0Kn2Q44yBP3+6GpxOGJjspi776cFG 6HksRW7sRN8c02krkrE7o0jE0LaKIpHKu6t3sqdX5MAH2tm8gPlu5LvSKABwuSOQOOx3 tFcA== X-Gm-Message-State: AOJu0YwcJjHGAiag+StHkSWzA//hxRPkCJw1o9cFh76Pa6lyl+5tWWTv W1Afryi1NI5PJw/zwC6Al+m0+5MDS96BYq3iNHbzDTu6fp1RmPlS5pAZ0oFW3oY3EaOnnJTLF6J s+A== X-Google-Smtp-Source: AGHT+IFl6cBrYkda8nNgdZrTivfv3zjTpKUU2f25L9umrr7vatGI4GPL+9fg9hOyModMI6oj7rvGWFpN3Tw= X-Received: from edliaw.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:305d]) (user=edliaw job=sendgmr) by 2002:a05:690c:4888:b0:6ad:e9c1:fc4f with SMTP id 00721157ae682-6d40f922d32mr317297b3.5.1725396012716; Tue, 03 Sep 2024 13:40:12 -0700 (PDT) Date: Tue, 3 Sep 2024 20:39:12 +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 2.46.0.469.g59c65b2a67-goog Message-ID: <20240903203915.3383774-1-edliaw@google.com> Subject: [PATCH RESEND] 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 , John Stultz , Stephen Boyd , Anna-Maria Behnsen , Frederic Weisbecker , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , Oleg Nesterov , Marco Elver , Dmitry Vyukov 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" 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") Reviewed-by: Muhammad Usama Anjum Signed-off-by: Edward Liaw 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 @@ =20 #define TEST_NAME "futex-requeue" #define timeout_ns 30000000 -#define WAKE_WAIT_US 10000 =20 volatile futex_t *f1; +static pthread_barrier_t barrier; =20 void usage(char *prog) { @@ -32,6 +32,8 @@ void *waiterfn(void *arg) to.tv_sec =3D 0; to.tv_nsec =3D timeout_ns; =20 + pthread_barrier_wait(&barrier); + if (futex_wait(f1, *f1, &to, 0)) printf("waiter failed errno %d\n", errno); =20 @@ -70,13 +72,15 @@ int main(int argc, char *argv[]) ksft_print_msg("%s: Test futex_requeue\n", basename(argv[0])); =20 + 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); =20 - usleep(WAKE_WAIT_US); + pthread_barrier_wait(&barrier); + pthread_barrier_destroy(&barrier); =20 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"); } =20 + pthread_barrier_init(&barrier, NULL, 11); =20 /* * 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); } =20 - usleep(WAKE_WAIT_US); + pthread_barrier_wait(&barrier); + pthread_barrier_destroy(&barrier); =20 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); --=20 2.46.0.469.g59c65b2a67-goog