| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-Id: <20251102224948.3906224-6-paulmck@kernel.org>
Date: Sun, 2 Nov 2025 14:49:46 -0800
From: "Paul E. McKenney" <paulmck@...nel.org>
To: rcu@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
kernel-team@...a.com,
rostedt@...dmis.org,
"Paul E. McKenney" <paulmck@...nel.org>
Subject: [PATCH 6/8] refscale: Add non-atomic per-CPU increment readers
This commit adds refscale readers based on READ_ONCE() and WRITE_ONCE()
that are unprotected (can lose counts, "refscale.scale_type=incpercpu"),
preempt-disabled ("refscale.scale_type=incpercpupreempt"),
bh-disabled ("refscale.scale_type=incpercpubh"), and irq-disabled
("refscale.scale_type=incpercpuirqsave"). On my x86 laptop, these are
about 4.3ns, 3.8ns, and 7.3ns per pair, respectively.
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
kernel/rcu/refscale.c | 155 +++++++++++++++++++++++++++++++++++++++++-
1 file changed, 153 insertions(+), 2 deletions(-)
diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index 479d86cad652..2b247355de40 100644
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -389,6 +389,155 @@ static const struct ref_scale_ops percpuinc_ops = {
.name = "percpuinc"
};
+// Note that this can lose counts in preemptible kernels.
+static void ref_incpercpu_section(const int nloops)
+{
+ int i;
+
+ for (i = nloops; i >= 0; i--) {
+ unsigned long *tap = this_cpu_ptr(&test_acqrel);
+
+ WRITE_ONCE(*tap, READ_ONCE(*tap) + 1);
+ WRITE_ONCE(*tap, READ_ONCE(*tap) - 1);
+ }
+}
+
+static void ref_incpercpu_delay_section(const int nloops, const int udl, const int ndl)
+{
+ int i;
+
+ for (i = nloops; i >= 0; i--) {
+ unsigned long *tap = this_cpu_ptr(&test_acqrel);
+
+ WRITE_ONCE(*tap, READ_ONCE(*tap) + 1);
+ un_delay(udl, ndl);
+ WRITE_ONCE(*tap, READ_ONCE(*tap) - 1);
+ }
+}
+
+static const struct ref_scale_ops incpercpu_ops = {
+ .init = rcu_sync_scale_init,
+ .readsection = ref_incpercpu_section,
+ .delaysection = ref_incpercpu_delay_section,
+ .name = "incpercpu"
+};
+
+static void ref_incpercpupreempt_section(const int nloops)
+{
+ int i;
+
+ for (i = nloops; i >= 0; i--) {
+ unsigned long *tap;
+
+ preempt_disable();
+ tap = this_cpu_ptr(&test_acqrel);
+ WRITE_ONCE(*tap, READ_ONCE(*tap) + 1);
+ WRITE_ONCE(*tap, READ_ONCE(*tap) - 1);
+ preempt_enable();
+ }
+}
+
+static void ref_incpercpupreempt_delay_section(const int nloops, const int udl, const int ndl)
+{
+ int i;
+
+ for (i = nloops; i >= 0; i--) {
+ unsigned long *tap;
+
+ preempt_disable();
+ tap = this_cpu_ptr(&test_acqrel);
+ WRITE_ONCE(*tap, READ_ONCE(*tap) + 1);
+ un_delay(udl, ndl);
+ WRITE_ONCE(*tap, READ_ONCE(*tap) - 1);
+ preempt_enable();
+ }
+}
+
+static const struct ref_scale_ops incpercpupreempt_ops = {
+ .init = rcu_sync_scale_init,
+ .readsection = ref_incpercpupreempt_section,
+ .delaysection = ref_incpercpupreempt_delay_section,
+ .name = "incpercpupreempt"
+};
+
+static void ref_incpercpubh_section(const int nloops)
+{
+ int i;
+
+ for (i = nloops; i >= 0; i--) {
+ unsigned long *tap;
+
+ local_bh_disable();
+ tap = this_cpu_ptr(&test_acqrel);
+ WRITE_ONCE(*tap, READ_ONCE(*tap) + 1);
+ WRITE_ONCE(*tap, READ_ONCE(*tap) - 1);
+ local_bh_enable();
+ }
+}
+
+static void ref_incpercpubh_delay_section(const int nloops, const int udl, const int ndl)
+{
+ int i;
+
+ for (i = nloops; i >= 0; i--) {
+ unsigned long *tap;
+
+ local_bh_disable();
+ tap = this_cpu_ptr(&test_acqrel);
+ WRITE_ONCE(*tap, READ_ONCE(*tap) + 1);
+ un_delay(udl, ndl);
+ WRITE_ONCE(*tap, READ_ONCE(*tap) - 1);
+ local_bh_enable();
+ }
+}
+
+static const struct ref_scale_ops incpercpubh_ops = {
+ .init = rcu_sync_scale_init,
+ .readsection = ref_incpercpubh_section,
+ .delaysection = ref_incpercpubh_delay_section,
+ .name = "incpercpubh"
+};
+
+static void ref_incpercpuirqsave_section(const int nloops)
+{
+ int i;
+ unsigned long flags;
+
+ for (i = nloops; i >= 0; i--) {
+ unsigned long *tap;
+
+ local_irq_save(flags);
+ tap = this_cpu_ptr(&test_acqrel);
+ WRITE_ONCE(*tap, READ_ONCE(*tap) + 1);
+ WRITE_ONCE(*tap, READ_ONCE(*tap) - 1);
+ local_irq_restore(flags);
+ }
+}
+
+static void ref_incpercpuirqsave_delay_section(const int nloops, const int udl, const int ndl)
+{
+ int i;
+ unsigned long flags;
+
+ for (i = nloops; i >= 0; i--) {
+ unsigned long *tap;
+
+ local_irq_save(flags);
+ tap = this_cpu_ptr(&test_acqrel);
+ WRITE_ONCE(*tap, READ_ONCE(*tap) + 1);
+ un_delay(udl, ndl);
+ WRITE_ONCE(*tap, READ_ONCE(*tap) - 1);
+ local_irq_restore(flags);
+ }
+}
+
+static const struct ref_scale_ops incpercpuirqsave_ops = {
+ .init = rcu_sync_scale_init,
+ .readsection = ref_incpercpuirqsave_section,
+ .delaysection = ref_incpercpuirqsave_delay_section,
+ .name = "incpercpuirqsave"
+};
+
// Definitions for rwlock
static rwlock_t test_rwlock;
@@ -1325,8 +1474,10 @@ ref_scale_init(void)
int firsterr = 0;
static const struct ref_scale_ops *scale_ops[] = {
&rcu_ops, &srcu_ops, &srcu_fast_ops, RCU_TRACE_OPS RCU_TASKS_OPS
- &refcnt_ops, &rwlock_ops, &rwsem_ops, &lock_ops, &lock_irq_ops,
- &percpuinc_ops, &acqrel_ops, &sched_clock_ops, &clock_ops, &jiffies_ops,
+ &refcnt_ops, &percpuinc_ops, &incpercpu_ops, &incpercpupreempt_ops,
+ &incpercpubh_ops, &incpercpuirqsave_ops,
+ &rwlock_ops, &rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops,
+ &sched_clock_ops, &clock_ops, &jiffies_ops,
&preempt_ops, &bh_ops, &irq_ops, &irqsave_ops,
&typesafe_ref_ops, &typesafe_lock_ops, &typesafe_seqlock_ops,
};
--
2.40.1
Powered by blists - more mailing lists