From: JP Kobryn <inwardvessel@xxxxxxxxx>
Using a higher value for the initial gp sequence counters allows for
wrapping to occur faster. It can help with surfacing any issues that may
be happening as a result of the wrap around.
Signed-off-by: JP Kobryn <inwardvessel@xxxxxxxxx>
Tested-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@xxxxxxxxxx>
---
include/linux/rcupdate.h | 3 +++
include/linux/srcutree.h | 15 ++++++++++++++-
kernel/rcu/rcu.h | 3 ---
kernel/rcu/srcutree.c | 7 ++++---
4 files changed, 21 insertions(+), 7 deletions(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 13f6f00aecf9..8d56db70d417 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -34,6 +34,9 @@
#define ULONG_CMP_GE(a, b) (ULONG_MAX / 2 >= (a) - (b))
#define ULONG_CMP_LT(a, b) (ULONG_MAX / 2 < (a) - (b))
+#define RCU_SEQ_CTR_SHIFT 2
+#define RCU_SEQ_STATE_MASK ((1 << RCU_SEQ_CTR_SHIFT) - 1)
+
/* Exported common interfaces */
void call_rcu(struct rcu_head *head, rcu_callback_t func);
void rcu_barrier_tasks(void);
diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
index 8f3f72480e78..ed57598394de 100644
--- a/include/linux/srcutree.h
+++ b/include/linux/srcutree.h
@@ -129,10 +129,23 @@ struct srcu_struct {
#define SRCU_STATE_SCAN1 1
#define SRCU_STATE_SCAN2 2
+/*
+ * Values for initializing gp sequence fields. Higher values allow wrap arounds to
+ * occur earlier.
+ * The second value with state is useful in the case of static initialization of
+ * srcu_usage where srcu_gp_seq_needed is expected to have some state value in its
+ * lower bits (or else it will appear to be already initialized within
+ * the call check_init_srcu_struct()).
+ */
+#define SRCU_GP_SEQ_INITIAL_VAL ((0UL - 100UL) << RCU_SEQ_CTR_SHIFT)
+#define SRCU_GP_SEQ_INITIAL_VAL_WITH_STATE (SRCU_GP_SEQ_INITIAL_VAL - 1)
+
#define __SRCU_USAGE_INIT(name) \
{ \
.lock = __SPIN_LOCK_UNLOCKED(name.lock), \
- .srcu_gp_seq_needed = -1UL, \
+ .srcu_gp_seq = SRCU_GP_SEQ_INITIAL_VAL, \
+ .srcu_gp_seq_needed = SRCU_GP_SEQ_INITIAL_VAL_WITH_STATE, \
+ .srcu_gp_seq_needed_exp = SRCU_GP_SEQ_INITIAL_VAL, \
.work = __DELAYED_WORK_INITIALIZER(name.work, NULL, 0), \
}
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index 38238e595a61..2bfed9855d67 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -54,9 +54,6 @@
* grace-period sequence number.
*/
-#define RCU_SEQ_CTR_SHIFT 2
-#define RCU_SEQ_STATE_MASK ((1 << RCU_SEQ_CTR_SHIFT) - 1)
-
/* Low-order bit definition for polled grace-period APIs. */
#define RCU_GET_STATE_COMPLETED 0x1
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index b24db425f16d..6fd9c914ce64 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -247,7 +247,7 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static)
mutex_init(&ssp->srcu_sup->srcu_cb_mutex);
mutex_init(&ssp->srcu_sup->srcu_gp_mutex);
ssp->srcu_idx = 0;
- ssp->srcu_sup->srcu_gp_seq = 0;
+ ssp->srcu_sup->srcu_gp_seq = SRCU_GP_SEQ_INITIAL_VAL;
ssp->srcu_sup->srcu_barrier_seq = 0;
mutex_init(&ssp->srcu_sup->srcu_barrier_mutex);
atomic_set(&ssp->srcu_sup->srcu_barrier_cpu_cnt, 0);
@@ -258,7 +258,7 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static)
if (!ssp->sda)
goto err_free_sup;
init_srcu_struct_data(ssp);
- ssp->srcu_sup->srcu_gp_seq_needed_exp = 0;
+ ssp->srcu_sup->srcu_gp_seq_needed_exp = SRCU_GP_SEQ_INITIAL_VAL;
ssp->srcu_sup->srcu_last_gp_end = ktime_get_mono_fast_ns();
if (READ_ONCE(ssp->srcu_sup->srcu_size_state) == SRCU_SIZE_SMALL && SRCU_SIZING_IS_INIT()) {
if (!init_srcu_struct_nodes(ssp, GFP_ATOMIC))
@@ -266,7 +266,8 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static)
WRITE_ONCE(ssp->srcu_sup->srcu_size_state, SRCU_SIZE_BIG);
}
ssp->srcu_sup->srcu_ssp = ssp;
- smp_store_release(&ssp->srcu_sup->srcu_gp_seq_needed, 0); /* Init done. */
+ smp_store_release(&ssp->srcu_sup->srcu_gp_seq_needed,
+ SRCU_GP_SEQ_INITIAL_VAL); /* Init done. */
return 0;
err_free_sda:
--
2.40.1
