On which, we should probably do this.
---
Subject: 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.
Cc: Rusty Russell <ru...@rustcorp.com.au>
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
---
kernel/module.c | 36 ++++++++----------------------------
1 file changed, 8 insertions(+), 28 deletions(-)
diff --git a/kernel/module.c b/kernel/module.c
index d856e96a3cce..98231bf59b6e 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2978,6 +2978,12 @@ 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
@@ -3120,32 +3126,6 @@ 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.
@@ -3165,8 +3145,8 @@ static int add_unformed_module(struct module *mod)
|| 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;
--
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