Commit 8c52cca0 authored by Waiman Long's avatar Waiman Long Committed by Ingo Molnar
Browse files

locking/locktorture: Fix incorrect use of ww_acquire_ctx in ww_mutex test 



The ww_acquire_ctx structure for ww_mutex needs to persist for a complete
lock/unlock cycle. In the ww_mutex test in locktorture, however, both
ww_acquire_init() and ww_acquire_fini() are called within the lock
function only. This causes a lockdep splat of "WARNING: Nested lock
was not taken" when lockdep is enabled in the kernel.

To fix this problem, we need to move the ww_acquire_fini() after
the ww_mutex_unlock() in torture_ww_mutex_unlock(). This is done by
allocating a global array of ww_acquire_ctx structures. Each locking
thread is associated with its own ww_acquire_ctx via the unique thread
id it has so that both the lock and unlock functions can access the
same ww_acquire_ctx structure.

Signed-off-by: default avatarWaiman Long <longman@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210318172814.4400-6-longman@redhat.com
parent aa3a5f31

kernel/locking/locktorture.c

+27 −12
Original line number Diff line number Diff line
@@ -374,15 +374,27 @@ static struct lock_torture_ops mutex_lock_ops = { 
 */

static DEFINE_WD_CLASS(torture_ww_class);

static struct ww_mutex torture_ww_mutex_0, torture_ww_mutex_1, torture_ww_mutex_2;

static struct ww_acquire_ctx *ww_acquire_ctxs;



static void torture_ww_mutex_init(void)

{

	ww_mutex_init(&torture_ww_mutex_0, &torture_ww_class);

	ww_mutex_init(&torture_ww_mutex_1, &torture_ww_class);

	ww_mutex_init(&torture_ww_mutex_2, &torture_ww_class);



	ww_acquire_ctxs = kmalloc_array(cxt.nrealwriters_stress,

					sizeof(*ww_acquire_ctxs),

					GFP_KERNEL);

	if (!ww_acquire_ctxs)

		VERBOSE_TOROUT_STRING("ww_acquire_ctx: Out of memory");

}



static void torture_ww_mutex_exit(void)

{

	kfree(ww_acquire_ctxs);

}



static int torture_ww_mutex_lock(int tid __maybe_unused)

static int torture_ww_mutex_lock(int tid)

__acquires(torture_ww_mutex_0)

__acquires(torture_ww_mutex_1)

__acquires(torture_ww_mutex_2)
@@ -392,7 +404,7 @@ __acquires(torture_ww_mutex_2) 
		struct list_head link;

		struct ww_mutex *lock;

	} locks[3], *ll, *ln;

	struct ww_acquire_ctx ctx;

	struct ww_acquire_ctx *ctx = &ww_acquire_ctxs[tid];



	locks[0].lock = &torture_ww_mutex_0;

	list_add(&locks[0].link, &list);
@@ -403,12 +415,12 @@ __acquires(torture_ww_mutex_2) 
	locks[2].lock = &torture_ww_mutex_2;

	list_add(&locks[2].link, &list);



	ww_acquire_init(&ctx, &torture_ww_class);

	ww_acquire_init(ctx, &torture_ww_class);



	list_for_each_entry(ll, &list, link) {

		int err;



		err = ww_mutex_lock(ll->lock, &ctx);

		err = ww_mutex_lock(ll->lock, ctx);

		if (!err)

			continue;
@@ -419,26 +431,29 @@ __acquires(torture_ww_mutex_2) 
		if (err != -EDEADLK)

			return err;



		ww_mutex_lock_slow(ll->lock, &ctx);

		ww_mutex_lock_slow(ll->lock, ctx);

		list_move(&ll->link, &list);

	}



	ww_acquire_fini(&ctx);

	return 0;

}



static void torture_ww_mutex_unlock(int tid __maybe_unused)

static void torture_ww_mutex_unlock(int tid)

__releases(torture_ww_mutex_0)

__releases(torture_ww_mutex_1)

__releases(torture_ww_mutex_2)

{

	struct ww_acquire_ctx *ctx = &ww_acquire_ctxs[tid];



	ww_mutex_unlock(&torture_ww_mutex_0);

	ww_mutex_unlock(&torture_ww_mutex_1);

	ww_mutex_unlock(&torture_ww_mutex_2);

	ww_acquire_fini(ctx);

}



static struct lock_torture_ops ww_mutex_lock_ops = {

	.init		= torture_ww_mutex_init,

	.exit		= torture_ww_mutex_exit,

	.writelock	= torture_ww_mutex_lock,

	.write_delay	= torture_mutex_delay,

	.task_boost     = torture_boost_dummy,
@@ -924,16 +939,16 @@ static int __init lock_torture_init(void) 
		goto unwind;

	}



	if (cxt.cur_ops->init) {

		cxt.cur_ops->init();

		cxt.init_called = true;

	}



	if (nwriters_stress >= 0)

		cxt.nrealwriters_stress = nwriters_stress;

	else

		cxt.nrealwriters_stress = 2 * num_online_cpus();



	if (cxt.cur_ops->init) {

		cxt.cur_ops->init();

		cxt.init_called = true;

	}



#ifdef CONFIG_DEBUG_MUTEXES

	if (str_has_prefix(torture_type, "mutex"))

		cxt.debug_lock = true;