<dwmw2> why doesn't lockdep catch us calling synchronize_srcu() with
a lock held, and elsewhere obtaining that lock within an srcu critical
region ("read lock") ?
Because synchronize_srcu() doesn't acquire the lock, merely checks that
it isn't held.
Would this work? Not even compile tested.
You can put my SoB on this if it works.
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index ca4b5dcec675..e9c2ab8369c0 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -1267,11 +1267,11 @@ static void __synchronize_srcu(struct srcu_struct *ssp, bool do_norm)
{
struct rcu_synchronize rcu;
- RCU_LOCKDEP_WARN(lockdep_is_held(ssp) ||
- lock_is_held(&rcu_bh_lock_map) ||
+ rcu_lock_acquire(&ssp->dep_map);
+ RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) ||
lock_is_held(&rcu_lock_map) ||
lock_is_held(&rcu_sched_lock_map),
- "Illegal synchronize_srcu() in same-type SRCU (or in RCU) read-side critical section");
+ "Illegal synchronize_srcu() in RCU read-side critical section");
if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE)
return;
@@ -1282,6 +1282,7 @@ static void __synchronize_srcu(struct srcu_struct *ssp, bool do_norm)
__call_srcu(ssp, &rcu.head, wakeme_after_rcu, do_norm);
wait_for_completion(&rcu.completion);
destroy_rcu_head_on_stack(&rcu.head);
+ rcu_lock_release(&ssp->dep_map);
/*
* Make sure that later code is ordered after the SRCU grace
