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Subject[PATCH 2/2] srcu: reduce scans of srcu_data in counter wrap check
Date
This patch reduce scans of srcu_data in case of a srcu_struct
tree have more than one levels

Signed-off-by: Ildar Ismagilov <devix84@gmail.com>
---
kernel/rcu/srcutree.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index c54617280245..2268381706d2 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -500,6 +500,7 @@ static void srcu_gp_end(struct srcu_struct *sp)
{
unsigned long cbdelay;
bool cbs;
+ bool last_lvl;
int cpu;
unsigned long flags;
unsigned long gpseq;
@@ -532,7 +533,8 @@ static void srcu_gp_end(struct srcu_struct *sp)
rcu_for_each_node_breadth_first(sp, snp) {
raw_spin_lock_irq_rcu_node(snp);
cbs = false;
- if (snp >= sp->level[rcu_num_lvls - 1])
+ last_lvl = snp >= sp->level[rcu_num_lvls - 1];
+ if (last_lvl)
cbs = snp->srcu_have_cbs[idx] == gpseq;
snp->srcu_have_cbs[idx] = gpseq;
rcu_seq_set_state(&snp->srcu_have_cbs[idx], 1);
@@ -545,7 +547,7 @@ static void srcu_gp_end(struct srcu_struct *sp)
srcu_schedule_cbs_snp(sp, snp, mask, cbdelay);

/* Occasionally prevent srcu_data counter wrap. */
- if (!(gpseq & counter_wrap_check))
+ if (!(gpseq & counter_wrap_check) && last_lvl)
for (cpu = snp->grplo; cpu <= snp->grphi; cpu++) {
sdp = per_cpu_ptr(sp->sda, cpu);
raw_spin_lock_irqsave_rcu_node(sdp, flags);
--
2.11.0
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