Commit-ID: d1b42b800e5d09dcee52812b4396aca3a3696ba9 Gitweb: http://git.kernel.org/tip/d1b42b800e5d09dcee52812b4396aca3a3696ba9 Author: Chris Wilson <ch...@chris-wilson.co.uk> AuthorDate: Thu, 1 Dec 2016 11:47:09 +0000 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Sat, 14 Jan 2017 11:37:16 +0100
locking/ww_mutex: Add kselftests for resolving ww_mutex cyclic deadlocks Check that ww_mutexes can detect cyclic deadlocks (generalised ABBA cycles) and resolve them by lock reordering. Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Maarten Lankhorst <d...@mblankhorst.nl> Cc: Nicolai Hähnle <nhaeh...@gmail.com> Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Link: http://lkml.kernel.org/r/20161201114711.28697-7-ch...@chris-wilson.co.uk Signed-off-by: Ingo Molnar <mi...@kernel.org> --- 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 5a643ba..84da738 100644 --- a/kernel/locking/test-ww_mutex.c +++ b/kernel/locking/test-ww_mutex.c @@ -21,9 +21,11 @@ #include <linux/completion.h> #include <linux/kthread.h> #include <linux/module.h> +#include <linux/slab.h> #include <linux/ww_mutex.h> 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);
