linux/kernel/locking/test-ww_mutex.c
Guenter Roeck e4a02ed2aa locking/ww_mutex: Fix runtime warning in the WW mutex selftest
If CONFIG_WW_MUTEX_SELFTEST=y is enabled, booting an image
in an arm64 virtual machine results in the following
traceback if 8 CPUs are enabled:

  DEBUG_LOCKS_WARN_ON(__owner_task(owner) != current)
  WARNING: CPU: 2 PID: 537 at kernel/locking/mutex.c:1033 __mutex_unlock_slowpath+0x1a8/0x2e0
  ...
  Call trace:
   __mutex_unlock_slowpath()
   ww_mutex_unlock()
   test_cycle_work()
   process_one_work()
   worker_thread()
   kthread()
   ret_from_fork()

If requesting b_mutex fails with -EDEADLK, the error variable
is reassigned to the return value from calling ww_mutex_lock
on a_mutex again. If this call fails, a_mutex is not locked.
It is, however, unconditionally unlocked subsequently, causing
the reported warning. Fix the problem by using two error variables.

With this change, the selftest still fails as follows:

  cyclic deadlock not resolved, ret[7/8] = -35

However, the traceback is gone.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Fixes: d1b42b800e ("locking/ww_mutex: Add kselftests for resolving ww_mutex cyclic deadlocks")
Link: http://lkml.kernel.org/r/1538516929-9734-1-git-send-email-linux@roeck-us.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-10-03 08:56:31 +02:00

648 lines
13 KiB
C

/*
* Module-based API test facility for ww_mutexes
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, you can access it online at
* http://www.gnu.org/licenses/gpl-2.0.html.
*/
#include <linux/kernel.h>
#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/kthread.h>
#include <linux/module.h>
#include <linux/random.h>
#include <linux/slab.h>
#include <linux/ww_mutex.h>
static DEFINE_WD_CLASS(ww_class);
struct workqueue_struct *wq;
struct test_mutex {
struct work_struct work;
struct ww_mutex mutex;
struct completion ready, go, done;
unsigned int flags;
};
#define TEST_MTX_SPIN BIT(0)
#define TEST_MTX_TRY BIT(1)
#define TEST_MTX_CTX BIT(2)
#define __TEST_MTX_LAST BIT(3)
static void test_mutex_work(struct work_struct *work)
{
struct test_mutex *mtx = container_of(work, typeof(*mtx), work);
complete(&mtx->ready);
wait_for_completion(&mtx->go);
if (mtx->flags & TEST_MTX_TRY) {
while (!ww_mutex_trylock(&mtx->mutex))
cond_resched();
} else {
ww_mutex_lock(&mtx->mutex, NULL);
}
complete(&mtx->done);
ww_mutex_unlock(&mtx->mutex);
}
static int __test_mutex(unsigned int flags)
{
#define TIMEOUT (HZ / 16)
struct test_mutex mtx;
struct ww_acquire_ctx ctx;
int ret;
ww_mutex_init(&mtx.mutex, &ww_class);
ww_acquire_init(&ctx, &ww_class);
INIT_WORK_ONSTACK(&mtx.work, test_mutex_work);
init_completion(&mtx.ready);
init_completion(&mtx.go);
init_completion(&mtx.done);
mtx.flags = flags;
schedule_work(&mtx.work);
wait_for_completion(&mtx.ready);
ww_mutex_lock(&mtx.mutex, (flags & TEST_MTX_CTX) ? &ctx : NULL);
complete(&mtx.go);
if (flags & TEST_MTX_SPIN) {
unsigned long timeout = jiffies + TIMEOUT;
ret = 0;
do {
if (completion_done(&mtx.done)) {
ret = -EINVAL;
break;
}
cond_resched();
} while (time_before(jiffies, timeout));
} else {
ret = wait_for_completion_timeout(&mtx.done, TIMEOUT);
}
ww_mutex_unlock(&mtx.mutex);
ww_acquire_fini(&ctx);
if (ret) {
pr_err("%s(flags=%x): mutual exclusion failure\n",
__func__, flags);
ret = -EINVAL;
}
flush_work(&mtx.work);
destroy_work_on_stack(&mtx.work);
return ret;
#undef TIMEOUT
}
static int test_mutex(void)
{
int ret;
int i;
for (i = 0; i < __TEST_MTX_LAST; i++) {
ret = __test_mutex(i);
if (ret)
return ret;
}
return 0;
}
static int test_aa(void)
{
struct ww_mutex mutex;
struct ww_acquire_ctx ctx;
int ret;
ww_mutex_init(&mutex, &ww_class);
ww_acquire_init(&ctx, &ww_class);
ww_mutex_lock(&mutex, &ctx);
if (ww_mutex_trylock(&mutex)) {
pr_err("%s: trylocked itself!\n", __func__);
ww_mutex_unlock(&mutex);
ret = -EINVAL;
goto out;
}
ret = ww_mutex_lock(&mutex, &ctx);
if (ret != -EALREADY) {
pr_err("%s: missed deadlock for recursing, ret=%d\n",
__func__, ret);
if (!ret)
ww_mutex_unlock(&mutex);
ret = -EINVAL;
goto out;
}
ret = 0;
out:
ww_mutex_unlock(&mutex);
ww_acquire_fini(&ctx);
return ret;
}
struct test_abba {
struct work_struct work;
struct ww_mutex a_mutex;
struct ww_mutex b_mutex;
struct completion a_ready;
struct completion b_ready;
bool resolve;
int result;
};
static void test_abba_work(struct work_struct *work)
{
struct test_abba *abba = container_of(work, typeof(*abba), work);
struct ww_acquire_ctx ctx;
int err;
ww_acquire_init(&ctx, &ww_class);
ww_mutex_lock(&abba->b_mutex, &ctx);
complete(&abba->b_ready);
wait_for_completion(&abba->a_ready);
err = ww_mutex_lock(&abba->a_mutex, &ctx);
if (abba->resolve && err == -EDEADLK) {
ww_mutex_unlock(&abba->b_mutex);
ww_mutex_lock_slow(&abba->a_mutex, &ctx);
err = ww_mutex_lock(&abba->b_mutex, &ctx);
}
if (!err)
ww_mutex_unlock(&abba->a_mutex);
ww_mutex_unlock(&abba->b_mutex);
ww_acquire_fini(&ctx);
abba->result = err;
}
static int test_abba(bool resolve)
{
struct test_abba abba;
struct ww_acquire_ctx ctx;
int err, ret;
ww_mutex_init(&abba.a_mutex, &ww_class);
ww_mutex_init(&abba.b_mutex, &ww_class);
INIT_WORK_ONSTACK(&abba.work, test_abba_work);
init_completion(&abba.a_ready);
init_completion(&abba.b_ready);
abba.resolve = resolve;
schedule_work(&abba.work);
ww_acquire_init(&ctx, &ww_class);
ww_mutex_lock(&abba.a_mutex, &ctx);
complete(&abba.a_ready);
wait_for_completion(&abba.b_ready);
err = ww_mutex_lock(&abba.b_mutex, &ctx);
if (resolve && err == -EDEADLK) {
ww_mutex_unlock(&abba.a_mutex);
ww_mutex_lock_slow(&abba.b_mutex, &ctx);
err = ww_mutex_lock(&abba.a_mutex, &ctx);
}
if (!err)
ww_mutex_unlock(&abba.b_mutex);
ww_mutex_unlock(&abba.a_mutex);
ww_acquire_fini(&ctx);
flush_work(&abba.work);
destroy_work_on_stack(&abba.work);
ret = 0;
if (resolve) {
if (err || abba.result) {
pr_err("%s: failed to resolve ABBA deadlock, A err=%d, B err=%d\n",
__func__, err, abba.result);
ret = -EINVAL;
}
} else {
if (err != -EDEADLK && abba.result != -EDEADLK) {
pr_err("%s: missed ABBA deadlock, A err=%d, B err=%d\n",
__func__, err, abba.result);
ret = -EINVAL;
}
}
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, erra = 0;
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) {
err = 0;
ww_mutex_unlock(&cycle->a_mutex);
ww_mutex_lock_slow(cycle->b_mutex, &ctx);
erra = ww_mutex_lock(&cycle->a_mutex, &ctx);
}
if (!err)
ww_mutex_unlock(cycle->b_mutex);
if (!erra)
ww_mutex_unlock(&cycle->a_mutex);
ww_acquire_fini(&ctx);
cycle->result = err ?: erra;
}
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("cyclic 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;
}
struct stress {
struct work_struct work;
struct ww_mutex *locks;
unsigned long timeout;
int nlocks;
};
static int *get_random_order(int count)
{
int *order;
int n, r, tmp;
order = kmalloc_array(count, sizeof(*order), GFP_KERNEL);
if (!order)
return order;
for (n = 0; n < count; n++)
order[n] = n;
for (n = count - 1; n > 1; n--) {
r = get_random_int() % (n + 1);
if (r != n) {
tmp = order[n];
order[n] = order[r];
order[r] = tmp;
}
}
return order;
}
static void dummy_load(struct stress *stress)
{
usleep_range(1000, 2000);
}
static void stress_inorder_work(struct work_struct *work)
{
struct stress *stress = container_of(work, typeof(*stress), work);
const int nlocks = stress->nlocks;
struct ww_mutex *locks = stress->locks;
struct ww_acquire_ctx ctx;
int *order;
order = get_random_order(nlocks);
if (!order)
return;
do {
int contended = -1;
int n, err;
ww_acquire_init(&ctx, &ww_class);
retry:
err = 0;
for (n = 0; n < nlocks; n++) {
if (n == contended)
continue;
err = ww_mutex_lock(&locks[order[n]], &ctx);
if (err < 0)
break;
}
if (!err)
dummy_load(stress);
if (contended > n)
ww_mutex_unlock(&locks[order[contended]]);
contended = n;
while (n--)
ww_mutex_unlock(&locks[order[n]]);
if (err == -EDEADLK) {
ww_mutex_lock_slow(&locks[order[contended]], &ctx);
goto retry;
}
if (err) {
pr_err_once("stress (%s) failed with %d\n",
__func__, err);
break;
}
ww_acquire_fini(&ctx);
} while (!time_after(jiffies, stress->timeout));
kfree(order);
kfree(stress);
}
struct reorder_lock {
struct list_head link;
struct ww_mutex *lock;
};
static void stress_reorder_work(struct work_struct *work)
{
struct stress *stress = container_of(work, typeof(*stress), work);
LIST_HEAD(locks);
struct ww_acquire_ctx ctx;
struct reorder_lock *ll, *ln;
int *order;
int n, err;
order = get_random_order(stress->nlocks);
if (!order)
return;
for (n = 0; n < stress->nlocks; n++) {
ll = kmalloc(sizeof(*ll), GFP_KERNEL);
if (!ll)
goto out;
ll->lock = &stress->locks[order[n]];
list_add(&ll->link, &locks);
}
kfree(order);
order = NULL;
do {
ww_acquire_init(&ctx, &ww_class);
list_for_each_entry(ll, &locks, link) {
err = ww_mutex_lock(ll->lock, &ctx);
if (!err)
continue;
ln = ll;
list_for_each_entry_continue_reverse(ln, &locks, link)
ww_mutex_unlock(ln->lock);
if (err != -EDEADLK) {
pr_err_once("stress (%s) failed with %d\n",
__func__, err);
break;
}
ww_mutex_lock_slow(ll->lock, &ctx);
list_move(&ll->link, &locks); /* restarts iteration */
}
dummy_load(stress);
list_for_each_entry(ll, &locks, link)
ww_mutex_unlock(ll->lock);
ww_acquire_fini(&ctx);
} while (!time_after(jiffies, stress->timeout));
out:
list_for_each_entry_safe(ll, ln, &locks, link)
kfree(ll);
kfree(order);
kfree(stress);
}
static void stress_one_work(struct work_struct *work)
{
struct stress *stress = container_of(work, typeof(*stress), work);
const int nlocks = stress->nlocks;
struct ww_mutex *lock = stress->locks + (get_random_int() % nlocks);
int err;
do {
err = ww_mutex_lock(lock, NULL);
if (!err) {
dummy_load(stress);
ww_mutex_unlock(lock);
} else {
pr_err_once("stress (%s) failed with %d\n",
__func__, err);
break;
}
} while (!time_after(jiffies, stress->timeout));
kfree(stress);
}
#define STRESS_INORDER BIT(0)
#define STRESS_REORDER BIT(1)
#define STRESS_ONE BIT(2)
#define STRESS_ALL (STRESS_INORDER | STRESS_REORDER | STRESS_ONE)
static int stress(int nlocks, int nthreads, unsigned int flags)
{
struct ww_mutex *locks;
int n;
locks = kmalloc_array(nlocks, sizeof(*locks), GFP_KERNEL);
if (!locks)
return -ENOMEM;
for (n = 0; n < nlocks; n++)
ww_mutex_init(&locks[n], &ww_class);
for (n = 0; nthreads; n++) {
struct stress *stress;
void (*fn)(struct work_struct *work);
fn = NULL;
switch (n & 3) {
case 0:
if (flags & STRESS_INORDER)
fn = stress_inorder_work;
break;
case 1:
if (flags & STRESS_REORDER)
fn = stress_reorder_work;
break;
case 2:
if (flags & STRESS_ONE)
fn = stress_one_work;
break;
}
if (!fn)
continue;
stress = kmalloc(sizeof(*stress), GFP_KERNEL);
if (!stress)
break;
INIT_WORK(&stress->work, fn);
stress->locks = locks;
stress->nlocks = nlocks;
stress->timeout = jiffies + 2*HZ;
queue_work(wq, &stress->work);
nthreads--;
}
flush_workqueue(wq);
for (n = 0; n < nlocks; n++)
ww_mutex_destroy(&locks[n]);
kfree(locks);
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;
ret = test_aa();
if (ret)
return ret;
ret = test_abba(false);
if (ret)
return ret;
ret = test_abba(true);
if (ret)
return ret;
ret = test_cycle(ncpus);
if (ret)
return ret;
ret = stress(16, 2*ncpus, STRESS_INORDER);
if (ret)
return ret;
ret = stress(16, 2*ncpus, STRESS_REORDER);
if (ret)
return ret;
ret = stress(4095, hweight32(STRESS_ALL)*ncpus, STRESS_ALL);
if (ret)
return ret;
return 0;
}
static void __exit test_ww_mutex_exit(void)
{
destroy_workqueue(wq);
}
module_init(test_ww_mutex_init);
module_exit(test_ww_mutex_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Intel Corporation");