module: Replace over-engineered nested sleep

Since the introduction of the nested sleep warning; we've established
that the occasional sleep inside a wait_event() is fine.

wait_event() loops are invariant wrt. spurious wakeups, and the
occasional sleep has a similar effect on them. As long as its occasional
its harmless.

Therefore replace the 'correct' but verbose wait_woken() thing with
a simple annotation to shut up the warning.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 8 insertions, 28 deletions

diff --git a/kernel/module.c b/kernel/module.c
index d7a92682fba3..82dc1f899e6d 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2984,6 +2984,12 @@ static bool finished_loading(const char *name)
         struct module *mod;
         bool ret;
 
+        /*
+         * The module_mutex should not be a heavily contended lock;
+         * if we get the occasional sleep here, we'll go an extra iteration
+         * in the wait_event_interruptible(), which is harmless.
+         */
+        sched_annotate_sleep();
         mutex_lock(&module_mutex);
         mod = find_module_all(name, strlen(name), true);
         ret = !mod || mod->state == MODULE_STATE_LIVE
@@ -3126,32 +3132,6 @@ static int may_init_module(void)
 }
 
 /*
- * Can't use wait_event_interruptible() because our condition
- * 'finished_loading()' contains a blocking primitive itself (mutex_lock).
- */
-static int wait_finished_loading(struct module *mod)
-{
-        DEFINE_WAIT_FUNC(wait, woken_wake_function);
-        int ret = 0;
-
-        add_wait_queue(&module_wq, &wait);
-        for (;;) {
-                if (finished_loading(mod->name))
-                        break;
-
-                if (signal_pending(current)) {
-                        ret = -ERESTARTSYS;
-                        break;
-                }
-
-                wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
-        }
-        remove_wait_queue(&module_wq, &wait);
-
-        return ret;
-}
-
-/*
  * We try to place it in the list now to make sure it's unique before
  * we dedicate too many resources.  In particular, temporary percpu
  * memory exhaustion.
@@ -3171,8 +3151,8 @@ again:
                     || old->state == MODULE_STATE_UNFORMED) {
                         /* Wait in case it fails to load. */
                         mutex_unlock(&module_mutex);
-
-                        err = wait_finished_loading(mod);
+                        err = wait_event_interruptible(module_wq,
+                                               finished_loading(mod->name));
                         if (err)
                                 goto out_unlocked;
                         goto again;