* [PATCH] rcuscale: Constify struct rcu_scale_ops
@ 2026-11-07 21:02 Christophe JAILLET
2026-11-07 23:25 ` Bradley Morgan
0 siblings, 1 reply; 2+ messages in thread
From: Christophe JAILLET @ 2026-11-07 21:02 UTC (permalink / raw)
To: Davidlohr Bueso, Paul E. McKenney, Josh Triplett,
Frederic Weisbecker, Neeraj Upadhyay, Joel Fernandes, Boqun Feng,
Uladzislau Rezki, Steven Rostedt, Mathieu Desnoyers,
Lai Jiangshan, Zqiang
Cc: linux-kernel, kernel-janitors, Christophe JAILLET, rcu
'struct rcu_scale_ops' is not modified in this driver.
Constifying these structures moves some data to a read-only section, so
increases overall security, especially when the structure holds some
function pointers.
On a x86_64, with allmodconfig:
Before:
======
text data bss dec hex filename
45585 24946 2816 73347 11e83 kernel/rcu/rcuscale.o
After:
=====
text data bss dec hex filename
46545 23986 2816 73347 11e83 kernel/rcu/rcuscale.o
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
Compile tested only.
---
kernel/rcu/rcuscale.c | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)
diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
index 1097ec15879c..522f7bc2e693 100644
--- a/kernel/rcu/rcuscale.c
+++ b/kernel/rcu/rcuscale.c
@@ -159,7 +159,7 @@ struct rcu_scale_ops {
const char *name;
};
-static struct rcu_scale_ops *cur_ops;
+static const struct rcu_scale_ops *cur_ops;
/*
* Definitions for rcu scalability testing.
@@ -185,7 +185,7 @@ static void rcu_sync_scale_init(void)
{
}
-static struct rcu_scale_ops rcu_ops = {
+static const struct rcu_scale_ops rcu_ops = {
.ptype = RCU_FLAVOR,
.init = rcu_sync_scale_init,
.readlock = rcu_scale_read_lock,
@@ -247,7 +247,7 @@ static void srcu_scale_synchronize_expedited(void)
synchronize_srcu_expedited(srcu_ctlp);
}
-static struct rcu_scale_ops srcu_ops = {
+static const struct rcu_scale_ops srcu_ops = {
.ptype = SRCU_FLAVOR,
.init = rcu_sync_scale_init,
.readlock = srcu_scale_read_lock,
@@ -276,7 +276,7 @@ static void srcu_sync_scale_cleanup(void)
cleanup_srcu_struct(srcu_ctlp);
}
-static struct rcu_scale_ops srcud_ops = {
+static const struct rcu_scale_ops srcud_ops = {
.ptype = SRCU_FLAVOR,
.init = srcu_sync_scale_init,
.cleanup = srcu_sync_scale_cleanup,
@@ -313,7 +313,7 @@ static void rcu_tasks_scale_stats(void)
rcu_tasks_torture_stats_print(scale_type, SCALE_FLAG);
}
-static struct rcu_scale_ops tasks_ops = {
+static const struct rcu_scale_ops tasks_ops = {
.ptype = RCU_TASKS_FLAVOR,
.init = rcu_sync_scale_init,
.readlock = tasks_scale_read_lock,
@@ -357,7 +357,7 @@ static void rcu_tasks_rude_scale_stats(void)
rcu_tasks_rude_torture_stats_print(scale_type, SCALE_FLAG);
}
-static struct rcu_scale_ops tasks_rude_ops = {
+static const struct rcu_scale_ops tasks_rude_ops = {
.ptype = RCU_TASKS_RUDE_FLAVOR,
.init = rcu_sync_scale_init,
.readlock = tasks_rude_scale_read_lock,
@@ -396,7 +396,7 @@ static void tasks_trace_scale_read_unlock(int idx)
rcu_read_unlock_trace();
}
-static struct rcu_scale_ops tasks_tracing_ops = {
+static const struct rcu_scale_ops tasks_tracing_ops = {
.ptype = RCU_TASKS_FLAVOR,
.init = rcu_sync_scale_init,
.readlock = tasks_trace_scale_read_lock,
@@ -693,7 +693,7 @@ rcu_scale_writer(void *arg)
}
static void
-rcu_scale_print_module_parms(struct rcu_scale_ops *cur_ops, const char *tag)
+rcu_scale_print_module_parms(const struct rcu_scale_ops *cur_ops, const char *tag)
{
pr_alert("%s" SCALE_FLAG
"--- %s: gp_async=%d gp_async_max=%d gp_exp=%d holdoff=%d minruntime=%d nreaders=%d nwriters=%d nexp=%d exp_interval=%d writer_holdoff=%d writer_holdoff_jiffies=%d verbose=%d shutdown_secs=%d\n",
@@ -1109,7 +1109,7 @@ rcu_scale_init(void)
int firsterr = 0;
long i;
long j;
- static struct rcu_scale_ops *scale_ops[] = {
+ static const struct rcu_scale_ops *scale_ops[] = {
&rcu_ops, &srcu_ops, &srcud_ops, TASKS_OPS TASKS_RUDE_OPS TASKS_TRACING_OPS
};
--
2.56.0
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] rcuscale: Constify struct rcu_scale_ops
2026-11-07 21:02 [PATCH] rcuscale: Constify struct rcu_scale_ops Christophe JAILLET
@ 2026-11-07 23:25 ` Bradley Morgan
0 siblings, 0 replies; 2+ messages in thread
From: Bradley Morgan @ 2026-11-07 23:25 UTC (permalink / raw)
To: christophe.jaillet
Cc: boqun, dave, frederic, jiangshanlai, joelagnelf, josh,
kernel-janitors, linux-kernel, mathieu.desnoyers,
neeraj.upadhyay, paulmck, qiang.zhang, rcu, rostedt, urezki
On 7 November 2026 21:02:25 GMT, Christophe JAILLET
<christophe.jaillet@wanadoo.fr> wrote:
>'struct rcu_scale_ops' is not modified in this driver.
>
>Constifying these structures moves some data to a read-only section, so
>increases overall security, especially when the structure holds some
>function pointers.
>
>On a x86_64, with allmodconfig:
>Before:
>======
> text data bss dec hex filename
> 45585 24946 2816 73347 11e83 kernel/rcu/rcuscale.o
>
>After:
>=====
> text data bss dec hex filename
> 46545 23986 2816 73347 11e83 kernel/rcu/rcuscale.o
>
Well, thanks. so you just consted rcu_scale_ops()? Uhh, well, this makes
enough sense to be feasible
Reviewed-by: Bradley Morgan
<brads@mainlining.org>
But how is this worth it? Why doesn't this work now? how will this make it
better? Those are my questions.
Well, I'm shrugging, but my tag would stand here, because it won't break
anything in particular.
>Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
>---
>Compile tested only.
>---
> kernel/rcu/rcuscale.c | 18 +++++++++---------
> 1 file changed, 9 insertions(+), 9 deletions(-)
>
>diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
>index 1097ec15879c..522f7bc2e693 100644
>--- a/kernel/rcu/rcuscale.c
>+++ b/kernel/rcu/rcuscale.c
>@@ -159,7 +159,7 @@ struct rcu_scale_ops {
> const char *name;
> };
>
>-static struct rcu_scale_ops *cur_ops;
>+static const struct rcu_scale_ops *cur_ops;
>
> /*
> * Definitions for rcu scalability testing.
>@@ -185,7 +185,7 @@ static void rcu_sync_scale_init(void)
> {
> }
>
>-static struct rcu_scale_ops rcu_ops = {
>+static const struct rcu_scale_ops rcu_ops = {
> .ptype = RCU_FLAVOR,
> .init = rcu_sync_scale_init,
> .readlock = rcu_scale_read_lock,
>@@ -247,7 +247,7 @@ static void srcu_scale_synchronize_expedited(void)
> synchronize_srcu_expedited(srcu_ctlp);
> }
>
>-static struct rcu_scale_ops srcu_ops = {
>+static const struct rcu_scale_ops srcu_ops = {
> .ptype = SRCU_FLAVOR,
> .init = rcu_sync_scale_init,
> .readlock = srcu_scale_read_lock,
>@@ -276,7 +276,7 @@ static void srcu_sync_scale_cleanup(void)
> cleanup_srcu_struct(srcu_ctlp);
> }
>
>-static struct rcu_scale_ops srcud_ops = {
>+static const struct rcu_scale_ops srcud_ops = {
> .ptype = SRCU_FLAVOR,
> .init = srcu_sync_scale_init,
> .cleanup = srcu_sync_scale_cleanup,
>@@ -313,7 +313,7 @@ static void rcu_tasks_scale_stats(void)
> rcu_tasks_torture_stats_print(scale_type, SCALE_FLAG);
> }
>
>-static struct rcu_scale_ops tasks_ops = {
>+static const struct rcu_scale_ops tasks_ops = {
> .ptype = RCU_TASKS_FLAVOR,
> .init = rcu_sync_scale_init,
> .readlock = tasks_scale_read_lock,
>@@ -357,7 +357,7 @@ static void rcu_tasks_rude_scale_stats(void)
> rcu_tasks_rude_torture_stats_print(scale_type, SCALE_FLAG);
> }
>
>-static struct rcu_scale_ops tasks_rude_ops = {
>+static const struct rcu_scale_ops tasks_rude_ops = {
> .ptype = RCU_TASKS_RUDE_FLAVOR,
> .init = rcu_sync_scale_init,
> .readlock = tasks_rude_scale_read_lock,
>@@ -396,7 +396,7 @@ static void tasks_trace_scale_read_unlock(int idx)
> rcu_read_unlock_trace();
> }
>
>-static struct rcu_scale_ops tasks_tracing_ops = {
>+static const struct rcu_scale_ops tasks_tracing_ops = {
> .ptype = RCU_TASKS_FLAVOR,
> .init = rcu_sync_scale_init,
> .readlock = tasks_trace_scale_read_lock,
>@@ -693,7 +693,7 @@ rcu_scale_writer(void *arg)
> }
>
> static void
>-rcu_scale_print_module_parms(struct rcu_scale_ops *cur_ops, const char *tag)
>+rcu_scale_print_module_parms(const struct rcu_scale_ops *cur_ops, const char *tag)
> {
> pr_alert("%s" SCALE_FLAG
> "--- %s: gp_async=%d gp_async_max=%d gp_exp=%d holdoff=%d minruntime=%d nreaders=%d nwriters=%d nexp=%d exp_interval=%d writer_holdoff=%d writer_holdoff_jiffies=%d verbose=%d shutdown_secs=%d\n",
>@@ -1109,7 +1109,7 @@ rcu_scale_init(void)
> int firsterr = 0;
> long i;
> long j;
>- static struct rcu_scale_ops *scale_ops[] = {
>+ static const struct rcu_scale_ops *scale_ops[] = {
> &rcu_ops, &srcu_ops, &srcud_ops, TASKS_OPS TASKS_RUDE_OPS TASKS_TRACING_OPS
> };
>
>
--- Thanks!
^ permalink raw reply [flat|nested] 2+ messages in thread
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