Once there are contention-initiated size transitions, it will be
possible for rcutorture to initiate a transition at the same time
as a contention-initiated transition. This commit therefore creates
a concurrency-safe helper function named srcu_transition_to_big() to
safely initiate size transitions.
Co-developed-by: Neeraj Upadhyay <quic_neeraju@xxxxxxxxxxx>
Signed-off-by: Neeraj Upadhyay <quic_neeraju@xxxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
kernel/rcu/srcutree.c | 23 +++++++++++++++++++++--
1 file changed, 21 insertions(+), 2 deletions(-)
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 64993a172cff..c9460374d437 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -272,6 +272,25 @@ EXPORT_SYMBOL_GPL(init_srcu_struct);
#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+/*
+ * Initiate an idempotent transition to SRCU_SIZE_BIG.
+ */
+static void srcu_transition_to_big(struct srcu_struct *ssp)
+{
+ unsigned long flags;
+
+ /* Double-checked locking on ->srcu_size-state. */
+ if (smp_load_acquire(&ssp->srcu_size_state) != SRCU_SIZE_SMALL)
+ return;
+ spin_lock_irqsave_rcu_node(ssp, flags);
+ if (smp_load_acquire(&ssp->srcu_size_state) != SRCU_SIZE_SMALL) {
+ spin_unlock_irqrestore_rcu_node(ssp, flags);
+ return;
+ }
+ smp_store_release(&ssp->srcu_size_state, SRCU_SIZE_ALLOC);
+ spin_unlock_irqrestore_rcu_node(ssp, flags);
+}
+
/*
* First-use initialization of statically allocated srcu_struct
* structure. Wiring up the combining tree is more than can be
@@ -1523,8 +1542,8 @@ void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf)
}
pr_cont(" T(%ld,%ld)\n", s0, s1);
}
- if (READ_ONCE(ssp->srcu_size_state) == SRCU_SIZE_SMALL && convert_to_big == 2)
- WRITE_ONCE(ssp->srcu_size_state, SRCU_SIZE_ALLOC);
+ if (convert_to_big == 2)
+ srcu_transition_to_big(ssp);
}
EXPORT_SYMBOL_GPL(srcu_torture_stats_print);
--
2.31.1.189.g2e36527f23
