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: Waiman Long <longman@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210318172814.4400-6-longman@redhat.com

diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index 90a975a..b3adb40 100644 (file)
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -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;