[PATCH v14 net-next 03/13] dpll: fix stale iteration in dpll_pin_on_pin_unregister()

[Grzegorz Nitka <grzegorz.nitka@intel.com>]

Neither parent->dpll_refs nor pin->dpll_refs on its own is a correct
iteration target at unregister time:

  - pin->dpll_refs includes DPLLs the child was registered against
    via a different parent or directly; blind unregister WARNs on
    the cookie miss in dpll_xa_ref_pin_del().
  - parent->dpll_refs reflects the parent's current attachments, not
    those at child-register time. Another driver may have (un)reg'd
    the parent against additional DPLLs in the meantime, so we miss
    registrations that exist and visit DPLLs that have none.

Walk pin->dpll_refs and use dpll_pin_registration_find() to filter
to entries whose cookie is this parent. Symmetric with
dpll_pin_on_pin_register(), correct under any subsequent change to
parent->dpll_refs.

Fixes: 9431063ad323 ("dpll: core: Add DPLL framework base functions")
Signed-off-by: Grzegorz Nitka <grzegorz.nitka@intel.com>
---
 drivers/dpll/dpll_core.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/dpll/dpll_core.c b/drivers/dpll/dpll_core.c
index 6dc7e93ece75..cea7e2be2cbc 100644
--- a/drivers/dpll/dpll_core.c
+++ b/drivers/dpll/dpll_core.c
@@ -1031,14 +1031,19 @@ EXPORT_SYMBOL_GPL(dpll_pin_on_pin_register);
 void dpll_pin_on_pin_unregister(struct dpll_pin *parent, struct dpll_pin *pin,
 				const struct dpll_pin_ops *ops, void *priv)
 {
+	struct dpll_pin_registration *reg;
 	struct dpll_pin_ref *ref;
 	unsigned long i;
 
 	mutex_lock(&dpll_lock);
 	dpll_pin_delete_ntf(pin);
 	dpll_xa_ref_pin_del(&pin->parent_refs, parent, ops, priv, pin);
-	xa_for_each(&pin->dpll_refs, i, ref)
+	xa_for_each(&pin->dpll_refs, i, ref) {
+		reg = dpll_pin_registration_find(ref, ops, priv, parent);
+		if (!reg)
+			continue;
 		__dpll_pin_unregister(ref->dpll, pin, ops, priv, parent);
+	}
 	mutex_unlock(&dpll_lock);
 }
 EXPORT_SYMBOL_GPL(dpll_pin_on_pin_unregister);
-- 
2.39.3