From patchwork Mon May 29 19:14:16 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mathieu Desnoyers X-Patchwork-Id: 70264 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 77AB43856603 for ; Mon, 29 May 2023 19:14:56 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 77AB43856603 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1685387696; bh=AG8T0dRwqEURuo50XJXwN0FInMeOvUVPZxn8hNbzcKU=; h=To:Cc:Subject:Date:In-Reply-To:References:List-Id: List-Unsubscribe:List-Archive:List-Post:List-Help:List-Subscribe: From:Reply-To:From; b=uUAaloDmy/+uETV7Wx0RKPdTxouEzaL9y5Wxzs7IHFPS9upiFwj7RMvk/RfDTUkfB Z2R9qE3ZL6YlRuih2Q41WS3BdZ8TVHAsesfJrYLjG6OH25jFRRTwRgEGKe0PVnxwez yB3nbcEzlI6m02egvRCqe9B0pTPwuvuilvCzV1EQ= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from smtpout.efficios.com (smtpout.efficios.com [167.114.26.122]) by sourceware.org (Postfix) with ESMTPS id 6917B385840E for ; Mon, 29 May 2023 19:14:24 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 6917B385840E 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) 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_Almeida?= , 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 X-Spam-Status: No, score=-11.8 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Mathieu Desnoyers via Libc-alpha From: Mathieu Desnoyers Reply-To: Mathieu Desnoyers Errors-To: libc-alpha-bounces+patchwork=sourceware.org@sourceware.org Sender: "Libc-alpha" 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/selftests/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/selftests/rseq/Makefile index 7c8f4f2be74c..a9d7ceb5b79b 100644 --- a/tools/testing/selftests/rseq/Makefile +++ b/tools/testing/selftests/rseq/Makefile @@ -14,7 +14,8 @@ OVERRIDE_TARGETS = 1 TEST_GEN_PROGS = basic_test basic_percpu_ops_test basic_percpu_ops_mm_cid_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 TEST_GEN_PROGS_EXTENDED = librseq.so diff --git a/tools/testing/selftests/rseq/rseq_mutex.c b/tools/testing/selftests/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 = { .owner = NULL }; + +static int testvar; + +static void rseq_lock_slowpath(struct rseq_mutex *lock) +{ + int i = 0; + + for (;;) { + struct rseq_abi_sched_state *expected = NULL, *self = 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 = NULL, *self = 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 = 0; i < 1000; i++) { + int var; + + rseq_lock(&lock); + var = 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 = 5; + pthread_t test_thread_id[nr_threads]; + int i; + + for (i = 0; i < nr_threads; i++) { + pthread_create(&test_thread_id[i], NULL, test_thread, NULL); + } + + for (i = 0; i < nr_threads; i++) { + pthread_join(test_thread_id[i], NULL); + } + + return 0; +}