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>

diff --git a/kernel/module.c b/kernel/module.c
index d7a92682fba366605161a06ffb1b4f8790b00e56..82dc1f899e6db9cd5f5f0c47ce16b01d89b0c734 100644 (file)
--- 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
@@ -3125,32 +3131,6 @@ static int may_init_module(void)
        return 0;
 }
 
-/*
- * 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
@@ -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;