From nobody Mon Feb 9 15:08:34 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C0CADC7EE2E for ; Mon, 29 May 2023 19:14:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229711AbjE2TO3 (ORCPT ); Mon, 29 May 2023 15:14:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50850 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229455AbjE2TO1 (ORCPT ); Mon, 29 May 2023 15:14:27 -0400 Received: from smtpout.efficios.com (unknown [IPv6:2607:5300:203:b2ee::31e5]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A1DE9DC; Mon, 29 May 2023 12:14:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=efficios.com; s=smtpout1; t=1685387664; bh=4iL71aqYe6mylgQi/BMhO/DWKge19ME73V8LmRUiL0k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JOryM4YHJrCJcZzUWSpChQleZcvut1kTGIIi7UFdFAE/7CiS+zzdzW052nujghcBL JJ2gaH2SB/CNXKa5sT3JBTRvmJrfA2VtAGeuUUCZEyUluxGWwzqu21PkZ5av/oK+zC QP9MryjatNN5GN28eOOM/mqsGR9Lz+5hERq2xXUD1G8BQbADOrtGcpWjMcQ4mw2SFJ dGSKFqu6RE3gThOyAXZ95I+LaTGDevfV15U5oYHnMi0JVXmVEmlqJqlYx4R9MxtQkW gIRMrhO8i6B5JFoya26rQiNKi6YV/2Qevg81Z5lPJKVbgjZidOktCFm3CxvPNUVe9S QpbUFNKg8Ts5w== Received: from localhost.localdomain (192-222-143-198.qc.cable.ebox.net [192.222.143.198]) by smtpout.efficios.com (Postfix) with ESMTPSA id 4QVQFC4LtVz165R; Mon, 29 May 2023 15:14:23 -0400 (EDT) From: Mathieu Desnoyers To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, Thomas Gleixner , "Paul E . McKenney" , Boqun Feng , "H . Peter Anvin" , Paul Turner , linux-api@vger.kernel.org, Christian Brauner , Florian Weimer , David.Laight@ACULAB.COM, carlos@redhat.com, Peter Oskolkov , Alexander Mikhalitsyn , Chris Kennelly , Ingo Molnar , Darren Hart , Davidlohr Bueso , =?UTF-8?q?Andr=C3=A9=20Almeida?= , libc-alpha@sourceware.org, Steven Rostedt , Jonathan Corbet , Noah Goldstein , Daniel Colascione , longman@redhat.com, Mathieu Desnoyers Subject: [RFC PATCH v2 4/4] selftests/rseq: Implement rseq_mutex test program Date: Mon, 29 May 2023 15:14:16 -0400 Message-Id: <20230529191416.53955-5-mathieu.desnoyers@efficios.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230529191416.53955-1-mathieu.desnoyers@efficios.com> References: <20230529191416.53955-1-mathieu.desnoyers@efficios.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Example use of the rseq sched state. Signed-off-by: Mathieu Desnoyers --- tools/testing/selftests/rseq/.gitignore | 1 + tools/testing/selftests/rseq/Makefile | 3 +- tools/testing/selftests/rseq/rseq_mutex.c | 120 ++++++++++++++++++++++ 3 files changed, 123 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/rseq/rseq_mutex.c diff --git a/tools/testing/selftests/rseq/.gitignore b/tools/testing/selfte= sts/rseq/.gitignore index a8db9f7a7cec..38d5b2fe5905 100644 --- a/tools/testing/selftests/rseq/.gitignore +++ b/tools/testing/selftests/rseq/.gitignore @@ -10,3 +10,4 @@ param_test_mm_cid param_test_mm_cid_benchmark param_test_mm_cid_compare_twice sched_state_test +rseq_mutex diff --git a/tools/testing/selftests/rseq/Makefile b/tools/testing/selftest= s/rseq/Makefile index 7c8f4f2be74c..a9d7ceb5b79b 100644 --- a/tools/testing/selftests/rseq/Makefile +++ b/tools/testing/selftests/rseq/Makefile @@ -14,7 +14,8 @@ OVERRIDE_TARGETS =3D 1 =20 TEST_GEN_PROGS =3D basic_test basic_percpu_ops_test basic_percpu_ops_mm_ci= d_test param_test \ param_test_benchmark param_test_compare_twice param_test_mm_cid \ - param_test_mm_cid_benchmark param_test_mm_cid_compare_twice sched_state_= test + param_test_mm_cid_benchmark param_test_mm_cid_compare_twice sched_state_= test \ + rseq_mutex =20 TEST_GEN_PROGS_EXTENDED =3D librseq.so =20 diff --git a/tools/testing/selftests/rseq/rseq_mutex.c b/tools/testing/self= tests/rseq/rseq_mutex.c new file mode 100644 index 000000000000..01afd6a0e8bd --- /dev/null +++ b/tools/testing/selftests/rseq/rseq_mutex.c @@ -0,0 +1,120 @@ +// SPDX-License-Identifier: LGPL-2.1 + +#define _GNU_SOURCE +#include +#include +#include +#include +#include +#include +#include + +#include "rseq.h" + +#define RSEQ_MUTEX_MAX_BUSY_LOOP 100 + +struct rseq_mutex { + /* + * When non-NULL, owner points to per-thread rseq_abi_sched_state of + * owner thread. + */ + struct rseq_abi_sched_state *owner; +}; + +static struct rseq_mutex lock =3D { .owner =3D NULL }; + +static int testvar; + +static void rseq_lock_slowpath(struct rseq_mutex *lock) +{ + int i =3D 0; + + for (;;) { + struct rseq_abi_sched_state *expected =3D NULL, *self =3D rseq_get_sched= _state(rseq_get_abi()); + + if (__atomic_compare_exchange_n(&lock->owner, &expected, self, false, + __ATOMIC_ACQUIRE, __ATOMIC_RELAXED)) + break; + //TODO: use rseq critical section to protect dereference of owner thread= 's + //rseq_abi_sched_state, combined with rseq fence at thread reclaim. + if ((RSEQ_READ_ONCE(expected->state) & RSEQ_ABI_SCHED_STATE_FLAG_ON_CPU)= && + i < RSEQ_MUTEX_MAX_BUSY_LOOP) { + rseq_barrier(); /* busy-wait, e.g. cpu_relax(). */ + i++; + } else { + //TODO: Enqueue waiter in a wait-queue, and integrate + //with sys_futex rather than waiting for 10ms. + (void) poll(NULL, 0, 10); /* wait 10ms */ + } + } +} + +static void rseq_lock(struct rseq_mutex *lock) +{ + struct rseq_abi_sched_state *expected =3D NULL, *self =3D rseq_get_sched_= state(rseq_get_abi()); + + if (__atomic_compare_exchange_n(&lock->owner, &expected, self, false, + __ATOMIC_ACQUIRE, __ATOMIC_RELAXED)) + return; + rseq_lock_slowpath(lock); +} + +static void rseq_unlock(struct rseq_mutex *lock) +{ + __atomic_store_n(&lock->owner, NULL, __ATOMIC_RELEASE); + //TODO: integrate with sys_futex and wakeup oldest waiter. +} + +static +void *test_thread(void *arg) +{ + int i; + + if (rseq_register_current_thread()) { + fprintf(stderr, "Error: rseq_register_current_thread(...) failed(%d): %s= \n", + errno, strerror(errno)); + abort(); + } + + for (i =3D 0; i < 1000; i++) { + int var; + + rseq_lock(&lock); + var =3D RSEQ_READ_ONCE(testvar); + if (var) { + fprintf(stderr, "Unexpected value %d\n", var); + abort(); + } + RSEQ_WRITE_ONCE(testvar, 1); + if (!(i % 10)) + (void) poll(NULL, 0, 10); + else + rseq_barrier(); + RSEQ_WRITE_ONCE(testvar, 0); + rseq_unlock(&lock); + } + + if (rseq_unregister_current_thread()) { + fprintf(stderr, "Error: rseq_unregister_current_thread(...) failed(%d): = %s\n", + errno, strerror(errno)); + abort(); + } + return NULL; +} + +int main(int argc, char **argv) +{ + int nr_threads =3D 5; + pthread_t test_thread_id[nr_threads]; + int i; + + for (i =3D 0; i < nr_threads; i++) { + pthread_create(&test_thread_id[i], NULL, test_thread, NULL); + } + + for (i =3D 0; i < nr_threads; i++) { + pthread_join(test_thread_id[i], NULL); + } + + return 0; +} --=20 2.25.1