From patchwork Sat Jun 2 12:44:06 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mathieu Desnoyers X-Patchwork-Id: 10444839 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id EDA73604D4 for ; Sat, 2 Jun 2018 12:48:08 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id DBA6C28A10 for ; Sat, 2 Jun 2018 12:48:08 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id CE71128A60; Sat, 2 Jun 2018 12:48:08 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI, T_DKIM_INVALID autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0D77928A10 for ; Sat, 2 Jun 2018 12:48:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751674AbeFBMqb (ORCPT ); Sat, 2 Jun 2018 08:46:31 -0400 Received: from mail.efficios.com ([167.114.142.138]:42760 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751685AbeFBMof (ORCPT ); Sat, 2 Jun 2018 08:44:35 -0400 Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id CF7D61A8672; Sat, 2 Jun 2018 08:44:34 -0400 (EDT) Received: from mail.efficios.com ([IPv6:::1]) by localhost (mail02.efficios.com [IPv6:::1]) (amavisd-new, port 10032) with ESMTP id 3fDDIsfkCQhy; Sat, 2 Jun 2018 08:44:34 -0400 (EDT) Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id 3BAD41A8664; Sat, 2 Jun 2018 08:44:34 -0400 (EDT) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com 3BAD41A8664 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1527943474; bh=d3meNWX0uOHls1Xp7vZAhvZn2W1HVU1URr1Fa2w4hcg=; h=From:To:Date:Message-Id; b=U5MIRUxWsktgY9KL9mHAWNlqdlxSPAjgMsdX3hYD2ccUL8mjC0jEa4ynmwu1W6g+1 Xt4UL/rCK0IGouL0N9Jy4igMKMJmC9hV0ZM61zABju08XbE5tCjJMDLyJqWR5gbrxj KQqFz7+YqSPgGzSGP01GSTZcK0+OKONaoyvDfthXfAmEjvPbj1RwbvTTTNC9x21lPy a1lG0BMBkKGeISJ9QlqNyrhlbQB5yAtqPNLjI7N0hjazv66PmzxIYrCnv/LctFV1jg Dwnkb6z7Aw1JJmTXpSHVDB2LnPpaOfJNdC/5jEhKypcYa3axIyg+JJqZOFF5yno6VJ y7fVFINimROFA== X-Virus-Scanned: amavisd-new at efficios.com Received: from mail.efficios.com ([IPv6:::1]) by localhost (mail02.efficios.com [IPv6:::1]) (amavisd-new, port 10026) with ESMTP id 7ZzLIgUC-Tkm; Sat, 2 Jun 2018 08:44:34 -0400 (EDT) Received: from thinkos.etherlink (192-222-157-41.qc.cable.ebox.net [192.222.157.41]) by mail.efficios.com (Postfix) with ESMTPSA id 0AF8E1A8648; Sat, 2 Jun 2018 08:44:33 -0400 (EDT) From: Mathieu Desnoyers To: Peter Zijlstra , "Paul E . McKenney" , Boqun Feng , Andy Lutomirski , Dave Watson Cc: linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Paul Turner , Andrew Morton , Russell King , Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , Andrew Hunter , Andi Kleen , Chris Lameter , Ben Maurer , Steven Rostedt , Josh Triplett , Linus Torvalds , Catalin Marinas , Will Deacon , Michael Kerrisk , Joel Fernandes , Mathieu Desnoyers , Shuah Khan , linux-kselftest@vger.kernel.org Subject: [RFC PATCH for 4.18 14/16] rseq: selftests: Provide basic percpu ops test (v2) Date: Sat, 2 Jun 2018 08:44:06 -0400 Message-Id: <20180602124408.8430-15-mathieu.desnoyers@efficios.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20180602124408.8430-1-mathieu.desnoyers@efficios.com> References: <20180602124408.8430-1-mathieu.desnoyers@efficios.com> Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP "basic_percpu_ops_test" is a slightly more "realistic" variant, implementing a few simple per-cpu operations and testing their correctness. Signed-off-by: Mathieu Desnoyers CC: Shuah Khan CC: Russell King CC: Catalin Marinas CC: Will Deacon CC: Thomas Gleixner CC: Paul Turner CC: Andrew Hunter CC: Peter Zijlstra CC: Andy Lutomirski CC: Andi Kleen CC: Dave Watson CC: Chris Lameter CC: Ingo Molnar CC: "H. Peter Anvin" CC: Ben Maurer CC: Steven Rostedt CC: "Paul E. McKenney" CC: Josh Triplett CC: Linus Torvalds CC: Andrew Morton CC: Boqun Feng CC: linux-kselftest@vger.kernel.org CC: linux-api@vger.kernel.org --- Changes since v1: - Use only rseq, remove use of cpu_opv system call. --- .../testing/selftests/rseq/basic_percpu_ops_test.c | 313 +++++++++++++++++++++ 1 file changed, 313 insertions(+) create mode 100644 tools/testing/selftests/rseq/basic_percpu_ops_test.c diff --git a/tools/testing/selftests/rseq/basic_percpu_ops_test.c b/tools/testing/selftests/rseq/basic_percpu_ops_test.c new file mode 100644 index 000000000000..96ef27905879 --- /dev/null +++ b/tools/testing/selftests/rseq/basic_percpu_ops_test.c @@ -0,0 +1,313 @@ +// SPDX-License-Identifier: LGPL-2.1 +#define _GNU_SOURCE +#include +#include +#include +#include +#include +#include +#include +#include + +#include "rseq.h" + +#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0])) + +struct percpu_lock_entry { + intptr_t v; +} __attribute__((aligned(128))); + +struct percpu_lock { + struct percpu_lock_entry c[CPU_SETSIZE]; +}; + +struct test_data_entry { + intptr_t count; +} __attribute__((aligned(128))); + +struct spinlock_test_data { + struct percpu_lock lock; + struct test_data_entry c[CPU_SETSIZE]; + int reps; +}; + +struct percpu_list_node { + intptr_t data; + struct percpu_list_node *next; +}; + +struct percpu_list_entry { + struct percpu_list_node *head; +} __attribute__((aligned(128))); + +struct percpu_list { + struct percpu_list_entry c[CPU_SETSIZE]; +}; + +/* A simple percpu spinlock. Returns the cpu lock was acquired on. */ +int rseq_this_cpu_lock(struct percpu_lock *lock) +{ + int cpu; + + for (;;) { + int ret; + + cpu = rseq_cpu_start(); + ret = rseq_cmpeqv_storev(&lock->c[cpu].v, + 0, 1, cpu); + if (rseq_likely(!ret)) + break; + /* Retry if comparison fails or rseq aborts. */ + } + /* + * Acquire semantic when taking lock after control dependency. + * Matches rseq_smp_store_release(). + */ + rseq_smp_acquire__after_ctrl_dep(); + return cpu; +} + +void rseq_percpu_unlock(struct percpu_lock *lock, int cpu) +{ + assert(lock->c[cpu].v == 1); + /* + * Release lock, with release semantic. Matches + * rseq_smp_acquire__after_ctrl_dep(). + */ + rseq_smp_store_release(&lock->c[cpu].v, 0); +} + +void *test_percpu_spinlock_thread(void *arg) +{ + struct spinlock_test_data *data = arg; + int i, cpu; + + if (rseq_register_current_thread()) { + fprintf(stderr, "Error: rseq_register_current_thread(...) failed(%d): %s\n", + errno, strerror(errno)); + abort(); + } + for (i = 0; i < data->reps; i++) { + cpu = rseq_this_cpu_lock(&data->lock); + data->c[cpu].count++; + rseq_percpu_unlock(&data->lock, cpu); + } + if (rseq_unregister_current_thread()) { + fprintf(stderr, "Error: rseq_unregister_current_thread(...) failed(%d): %s\n", + errno, strerror(errno)); + abort(); + } + + return NULL; +} + +/* + * A simple test which implements a sharded counter using a per-cpu + * lock. Obviously real applications might prefer to simply use a + * per-cpu increment; however, this is reasonable for a test and the + * lock can be extended to synchronize more complicated operations. + */ +void test_percpu_spinlock(void) +{ + const int num_threads = 200; + int i; + uint64_t sum; + pthread_t test_threads[num_threads]; + struct spinlock_test_data data; + + memset(&data, 0, sizeof(data)); + data.reps = 5000; + + for (i = 0; i < num_threads; i++) + pthread_create(&test_threads[i], NULL, + test_percpu_spinlock_thread, &data); + + for (i = 0; i < num_threads; i++) + pthread_join(test_threads[i], NULL); + + sum = 0; + for (i = 0; i < CPU_SETSIZE; i++) + sum += data.c[i].count; + + assert(sum == (uint64_t)data.reps * num_threads); +} + +void this_cpu_list_push(struct percpu_list *list, + struct percpu_list_node *node, + int *_cpu) +{ + int cpu; + + for (;;) { + intptr_t *targetptr, newval, expect; + int ret; + + cpu = rseq_cpu_start(); + /* Load list->c[cpu].head with single-copy atomicity. */ + expect = (intptr_t)RSEQ_READ_ONCE(list->c[cpu].head); + newval = (intptr_t)node; + targetptr = (intptr_t *)&list->c[cpu].head; + node->next = (struct percpu_list_node *)expect; + ret = rseq_cmpeqv_storev(targetptr, expect, newval, cpu); + if (rseq_likely(!ret)) + break; + /* Retry if comparison fails or rseq aborts. */ + } + if (_cpu) + *_cpu = cpu; +} + +/* + * Unlike a traditional lock-less linked list; the availability of a + * rseq primitive allows us to implement pop without concerns over + * ABA-type races. + */ +struct percpu_list_node *this_cpu_list_pop(struct percpu_list *list, + int *_cpu) +{ + for (;;) { + struct percpu_list_node *head; + intptr_t *targetptr, expectnot, *load; + off_t offset; + int ret, cpu; + + cpu = rseq_cpu_start(); + targetptr = (intptr_t *)&list->c[cpu].head; + expectnot = (intptr_t)NULL; + offset = offsetof(struct percpu_list_node, next); + load = (intptr_t *)&head; + ret = rseq_cmpnev_storeoffp_load(targetptr, expectnot, + offset, load, cpu); + if (rseq_likely(!ret)) { + if (_cpu) + *_cpu = cpu; + return head; + } + if (ret > 0) + return NULL; + /* Retry if rseq aborts. */ + } +} + +/* + * __percpu_list_pop is not safe against concurrent accesses. Should + * only be used on lists that are not concurrently modified. + */ +struct percpu_list_node *__percpu_list_pop(struct percpu_list *list, int cpu) +{ + struct percpu_list_node *node; + + node = list->c[cpu].head; + if (!node) + return NULL; + list->c[cpu].head = node->next; + return node; +} + +void *test_percpu_list_thread(void *arg) +{ + int i; + struct percpu_list *list = (struct percpu_list *)arg; + + if (rseq_register_current_thread()) { + fprintf(stderr, "Error: rseq_register_current_thread(...) failed(%d): %s\n", + errno, strerror(errno)); + abort(); + } + + for (i = 0; i < 100000; i++) { + struct percpu_list_node *node; + + node = this_cpu_list_pop(list, NULL); + sched_yield(); /* encourage shuffling */ + if (node) + this_cpu_list_push(list, node, NULL); + } + + if (rseq_unregister_current_thread()) { + fprintf(stderr, "Error: rseq_unregister_current_thread(...) failed(%d): %s\n", + errno, strerror(errno)); + abort(); + } + + return NULL; +} + +/* Simultaneous modification to a per-cpu linked list from many threads. */ +void test_percpu_list(void) +{ + int i, j; + uint64_t sum = 0, expected_sum = 0; + struct percpu_list list; + pthread_t test_threads[200]; + cpu_set_t allowed_cpus; + + memset(&list, 0, sizeof(list)); + + /* Generate list entries for every usable cpu. */ + sched_getaffinity(0, sizeof(allowed_cpus), &allowed_cpus); + for (i = 0; i < CPU_SETSIZE; i++) { + if (!CPU_ISSET(i, &allowed_cpus)) + continue; + for (j = 1; j <= 100; j++) { + struct percpu_list_node *node; + + expected_sum += j; + + node = malloc(sizeof(*node)); + assert(node); + node->data = j; + node->next = list.c[i].head; + list.c[i].head = node; + } + } + + for (i = 0; i < 200; i++) + pthread_create(&test_threads[i], NULL, + test_percpu_list_thread, &list); + + for (i = 0; i < 200; i++) + pthread_join(test_threads[i], NULL); + + for (i = 0; i < CPU_SETSIZE; i++) { + struct percpu_list_node *node; + + if (!CPU_ISSET(i, &allowed_cpus)) + continue; + + while ((node = __percpu_list_pop(&list, i))) { + sum += node->data; + free(node); + } + } + + /* + * All entries should now be accounted for (unless some external + * actor is interfering with our allowed affinity while this + * test is running). + */ + assert(sum == expected_sum); +} + +int main(int argc, char **argv) +{ + if (rseq_register_current_thread()) { + fprintf(stderr, "Error: rseq_register_current_thread(...) failed(%d): %s\n", + errno, strerror(errno)); + goto error; + } + printf("spinlock\n"); + test_percpu_spinlock(); + printf("percpu_list\n"); + test_percpu_list(); + if (rseq_unregister_current_thread()) { + fprintf(stderr, "Error: rseq_unregister_current_thread(...) failed(%d): %s\n", + errno, strerror(errno)); + goto error; + } + return 0; + +error: + return -1; +} +