Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757821AbcLALru (ORCPT ); Thu, 1 Dec 2016 06:47:50 -0500 Received: from mail-wj0-f195.google.com ([209.85.210.195]:33831 "EHLO mail-wj0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757238AbcLALre (ORCPT ); Thu, 1 Dec 2016 06:47:34 -0500 From: Chris Wilson To: linux-kernel@vger.kernel.org Cc: Chris Wilson , Peter Zijlstra , Ingo Molnar , Maarten Lankhorst , =?UTF-8?q?Nicolai=20H=C3=A4hnle?= Subject: [PATCH v2 6/8] locking: Add kselftests for resolving ww_mutex cyclic deadlocks Date: Thu, 1 Dec 2016 11:47:09 +0000 Message-Id: <20161201114711.28697-7-chris@chris-wilson.co.uk> X-Mailer: git-send-email 2.10.2 In-Reply-To: <20161201114711.28697-1-chris@chris-wilson.co.uk> References: <20161201114711.28697-1-chris@chris-wilson.co.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3720 Lines: 166 Check that ww_mutexes can detect cyclic deadlocks (generalised ABBA cycles) and resolve them by lock reordering. Signed-off-by: Chris Wilson Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Maarten Lankhorst Cc: Nicolai Hähnle --- kernel/locking/test-ww_mutex.c | 115 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 115 insertions(+) diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c index 5a643ba2b020..84da738e57d1 100644 --- a/kernel/locking/test-ww_mutex.c +++ b/kernel/locking/test-ww_mutex.c @@ -21,9 +21,11 @@ #include #include #include +#include #include static DEFINE_WW_CLASS(ww_class); +struct workqueue_struct *wq; struct test_mutex { struct work_struct work; @@ -243,10 +245,118 @@ static int test_abba(bool resolve) return ret; } +struct test_cycle { + struct work_struct work; + struct ww_mutex a_mutex; + struct ww_mutex *b_mutex; + struct completion *a_signal; + struct completion b_signal; + int result; +}; + +static void test_cycle_work(struct work_struct *work) +{ + struct test_cycle *cycle = container_of(work, typeof(*cycle), work); + struct ww_acquire_ctx ctx; + int err; + + ww_acquire_init(&ctx, &ww_class); + ww_mutex_lock(&cycle->a_mutex, &ctx); + + complete(cycle->a_signal); + wait_for_completion(&cycle->b_signal); + + err = ww_mutex_lock(cycle->b_mutex, &ctx); + if (err == -EDEADLK) { + ww_mutex_unlock(&cycle->a_mutex); + ww_mutex_lock_slow(cycle->b_mutex, &ctx); + err = ww_mutex_lock(&cycle->a_mutex, &ctx); + } + + if (!err) + ww_mutex_unlock(cycle->b_mutex); + ww_mutex_unlock(&cycle->a_mutex); + ww_acquire_fini(&ctx); + + cycle->result = err; +} + +static int __test_cycle(unsigned int nthreads) +{ + struct test_cycle *cycles; + unsigned int n, last = nthreads - 1; + int ret; + + cycles = kmalloc_array(nthreads, sizeof(*cycles), GFP_KERNEL); + if (!cycles) + return -ENOMEM; + + for (n = 0; n < nthreads; n++) { + struct test_cycle *cycle = &cycles[n]; + + ww_mutex_init(&cycle->a_mutex, &ww_class); + if (n == last) + cycle->b_mutex = &cycles[0].a_mutex; + else + cycle->b_mutex = &cycles[n + 1].a_mutex; + + if (n == 0) + cycle->a_signal = &cycles[last].b_signal; + else + cycle->a_signal = &cycles[n - 1].b_signal; + init_completion(&cycle->b_signal); + + INIT_WORK(&cycle->work, test_cycle_work); + cycle->result = 0; + } + + for (n = 0; n < nthreads; n++) + queue_work(wq, &cycles[n].work); + + flush_workqueue(wq); + + ret = 0; + for (n = 0; n < nthreads; n++) { + struct test_cycle *cycle = &cycles[n]; + + if (!cycle->result) + continue; + + pr_err("cylic deadlock not resolved, ret[%d/%d] = %d\n", + n, nthreads, cycle->result); + ret = -EINVAL; + break; + } + + for (n = 0; n < nthreads; n++) + ww_mutex_destroy(&cycles[n].a_mutex); + kfree(cycles); + return ret; +} + +static int test_cycle(unsigned int ncpus) +{ + unsigned int n; + int ret; + + for (n = 2; n <= ncpus + 1; n++) { + ret = __test_cycle(n); + if (ret) + return ret; + } + + return 0; +} + static int __init test_ww_mutex_init(void) { + int ncpus = num_online_cpus(); int ret; + wq = alloc_workqueue("test-ww_mutex", WQ_UNBOUND, 0); + if (!wq) + return -ENOMEM; + ret = test_mutex(); if (ret) return ret; @@ -263,11 +373,16 @@ static int __init test_ww_mutex_init(void) if (ret) return ret; + ret = test_cycle(ncpus); + if (ret) + return ret; + return 0; } static void __exit test_ww_mutex_exit(void) { + destroy_workqueue(wq); } module_init(test_ww_mutex_init); -- 2.10.2