When an srcu_struct structure is created (but not in a kernel module)
by DEFINE_SRCU() and friends, the per-CPU srcu_data structure is
statically allocated. In all other cases, that structure is obtained
from alloc_percpu(), in which case cleanup_srcu_struct() must invoke
free_percpu() on the resulting ->sda pointer in the srcu_struct pointer.
Which it does.
Except that it also invokes free_percpu() on the ->sda pointer
referencing the statically allocated per-CPU srcu_data structures.
Which free_percpu() is surprisingly OK with.
This commit nevertheless stops cleanup_srcu_struct() from freeing
statically allocated per-CPU srcu_data structures.
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
include/linux/srcutree.h | 1 +
kernel/rcu/srcutree.c | 13 +++++++++----
2 files changed, 10 insertions(+), 4 deletions(-)
diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
index 44e998643f483..44bd204498a11 100644
--- a/include/linux/srcutree.h
+++ b/include/linux/srcutree.h
@@ -73,6 +73,7 @@ struct srcu_struct {
unsigned long srcu_gp_seq_needed_exp; /* Furthest future exp GP. */
unsigned long srcu_last_gp_end; /* Last GP end timestamp (ns) */
struct srcu_data __percpu *sda; /* Per-CPU srcu_data array. */
+ bool sda_is_static; /* May ->sda be passed to free_percpu()? */
unsigned long srcu_barrier_seq; /* srcu_barrier seq #. */
struct mutex srcu_barrier_mutex; /* Serialize barrier ops. */
struct completion srcu_barrier_completion;
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 767487ad5440a..39dc3015dfeba 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -206,8 +206,11 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static)
mutex_init(&ssp->srcu_barrier_mutex);
atomic_set(&ssp->srcu_barrier_cpu_cnt, 0);
INIT_DELAYED_WORK(&ssp->work, process_srcu);
- if (!is_static)
+ ssp->sda_is_static = false;
+ if (!is_static) {
ssp->sda = alloc_percpu(struct srcu_data);
+ ssp->sda_is_static = true;
+ }
if (!ssp->sda)
return -ENOMEM;
init_srcu_struct_data(ssp);
@@ -215,7 +218,7 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static)
ssp->srcu_last_gp_end = ktime_get_mono_fast_ns();
if (READ_ONCE(ssp->srcu_size_state) == SRCU_SIZE_SMALL && convert_to_big == 1) {
if (!init_srcu_struct_nodes(ssp, GFP_ATOMIC)) {
- if (!is_static) {
+ if (ssp->sda_is_static) {
free_percpu(ssp->sda);
ssp->sda = NULL;
}
@@ -434,8 +437,10 @@ void cleanup_srcu_struct(struct srcu_struct *ssp)
rcu_seq_current(&ssp->srcu_gp_seq), ssp->srcu_gp_seq_needed);
return; /* Caller forgot to stop doing call_srcu()? */
}
- free_percpu(ssp->sda);
- ssp->sda = NULL;
+ if (ssp->sda_is_static) {
+ free_percpu(ssp->sda);
+ ssp->sda = NULL;
+ }
kfree(ssp->node);
ssp->node = NULL;
ssp->srcu_size_state = SRCU_SIZE_SMALL;
--
2.31.1.189.g2e36527f23
