[PATCH v6 46/52] opp: Put interconnect paths outside of opp_table_lock

[Dmitry Osipenko]

This patch fixes lockup which happens when OPP table is released if
interconnect provider uses OPP in the icc_provider->set() callback
and bandwidth of the ICC path is set to 0 by the ICC core when path
is released. The icc_put() doesn't need the opp_table_lock protection,
hence let's move it outside of the lock in order to resolve the problem.

In particular this fixes tegra-devfreq driver lockup on trying to unload
the driver module. The devfreq driver uses OPP-bandwidth API and its ICC
provider also uses OPP for DVFS, hence they both take same opp_table_lock
when OPP table of the devfreq is released.

Signed-off-by: Dmitry Osipenko <dig...@gmail.com>
---
 drivers/opp/core.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/drivers/opp/core.c b/drivers/opp/core.c
index 2483e765318a..1134df360fe0 100644
--- a/drivers/opp/core.c
+++ b/drivers/opp/core.c
@@ -1187,12 +1187,6 @@ static void _opp_table_kref_release(struct kref *kref)
        if (!IS_ERR(opp_table->clk))
                clk_put(opp_table->clk);
 
-       if (opp_table->paths) {
-               for (i = 0; i < opp_table->path_count; i++)
-                       icc_put(opp_table->paths[i]);
-               kfree(opp_table->paths);
-       }
-
        WARN_ON(!list_empty(&opp_table->opp_list));
 
        list_for_each_entry_safe(opp_dev, temp, &opp_table->dev_list, node) {
@@ -1209,9 +1203,22 @@ static void _opp_table_kref_release(struct kref *kref)
        mutex_destroy(&opp_table->genpd_virt_dev_lock);
        mutex_destroy(&opp_table->lock);
        list_del(&opp_table->node);
-       kfree(opp_table);
 
        mutex_unlock(&opp_table_lock);
+
+       /*
+        * Interconnect provider may use OPP too, hence icc_put() needs to be
+        * invoked outside of the opp_table_lock in order to prevent nested
+        * locking which happens when bandwidth of the ICC path is set to 0
+        * by ICC core on release of the path.
+        */
+       if (opp_table->paths) {
+               for (i = 0; i < opp_table->path_count; i++)
+                       icc_put(opp_table->paths[i]);
+               kfree(opp_table->paths);
+       }
+
+       kfree(opp_table);
 }
 
 void dev_pm_opp_put_opp_table(struct opp_table *opp_table)
-- 
2.27.0