Re: [PATCH] rcuscale: Constify struct rcu_scale_ops

[Bradley Morgan <brads@mainlining.org>]

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!