Since the srcu read lock is still held during srcu_funnel_gp_start(),
the seq snap should be the largest number for the slot
srcu_have_cbs[idx].
Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx>
Cc: Lai Jiangshan <jiangshanlai@xxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
Cc: Frederic Weisbecker <frederic@xxxxxxxxxx>
Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
To: rcu@xxxxxxxxxxxxxxx
---
include/linux/rcupdate.h | 1 +
kernel/rcu/srcutree.c | 10 +++++-----
2 files changed, 6 insertions(+), 5 deletions(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 08605ce7379d..a09007236660 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -32,6 +32,7 @@
#include <linux/context_tracking_irq.h>
#define ULONG_CMP_GE(a, b) (ULONG_MAX / 2 >= (a) - (b))
+#define ULONG_CMP_GT(a, b) (ULONG_MAX / 2 > (a) - (b))
#define ULONG_CMP_LT(a, b) (ULONG_MAX / 2 < (a) - (b))
#define ulong2long(a) (*(long *)(&(a)))
#define USHORT_CMP_GE(a, b) (USHRT_MAX / 2 >= (unsigned short)((a) - (b)))
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index c54d6c04751f..057752db1125 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -900,14 +900,14 @@ static void srcu_funnel_gp_start(struct srcu_struct *ssp, struct srcu_data *sdp,
for (snp = snp_leaf; snp != NULL; snp = snp->srcu_parent) {
spin_lock_irqsave_rcu_node(snp, flags);
snp_seq = snp->srcu_have_cbs[idx];
- if (!srcu_invl_snp_seq(snp_seq) && ULONG_CMP_GE(snp_seq, s)) {
+ /* s should be the biggest in the current slot. Hence only LE is
+ * valid
+ */
+ BUG_ON(ULONG_CMP_GT(snp_seq, s));
+ if (!srcu_invl_snp_seq(snp_seq) && (snp_seq == s)) {
if (snp == snp_leaf && snp_seq == s)
snp->srcu_data_have_cbs[idx] |= sdp->grpmask;
spin_unlock_irqrestore_rcu_node(snp, flags);
- if (snp == snp_leaf && snp_seq != s) {
- srcu_schedule_cbs_sdp(sdp, do_norm ? SRCU_INTERVAL : 0);
- return;
- }
if (!do_norm)
srcu_funnel_exp_start(ssp, snp, s);
return;
--
2.31.1
