[PATCH 1/2] OPP: Staticize `lazy_opp_tables` in of.c

[PATCH 1/2] OPP: Staticize `lazy_opp_tables` in of.c

[Viresh Kumar]

`lazy_opp_tables` is only used in of.c, move it there and mark it
`static`.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 drivers/opp/core.c | 3 ---
 drivers/opp/of.c   | 3 +++
 drivers/opp/opp.h  | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/opp/core.c b/drivers/opp/core.c
index 7046487dc6f4..9f918077cd62 100644
--- a/drivers/opp/core.c
+++ b/drivers/opp/core.c
@@ -29,9 +29,6 @@
  */
 LIST_HEAD(opp_tables);
 
-/* OPP tables with uninitialized required OPPs */
-LIST_HEAD(lazy_opp_tables);
-
 /* Lock to allow exclusive modification to the device and opp lists */
 DEFINE_MUTEX(opp_table_lock);
 /* Flag indicating that opp_tables list is being updated at the moment */
diff --git a/drivers/opp/of.c b/drivers/opp/of.c
index 8246e9b7afe7..c740a907ef76 100644
--- a/drivers/opp/of.c
+++ b/drivers/opp/of.c
@@ -21,6 +21,9 @@
 
 #include "opp.h"
 
+/* OPP tables with uninitialized required OPPs */
+static LIST_HEAD(lazy_opp_tables);
+
 /*
  * Returns opp descriptor node for a device node, caller must
  * do of_node_put().
diff --git a/drivers/opp/opp.h b/drivers/opp/opp.h
index 2a057c42ddf4..eb71385d96c1 100644
--- a/drivers/opp/opp.h
+++ b/drivers/opp/opp.h
@@ -26,7 +26,7 @@ struct regulator;
 /* Lock to allow exclusive modification to the device and opp lists */
 extern struct mutex opp_table_lock;
 
-extern struct list_head opp_tables, lazy_opp_tables;
+extern struct list_head opp_tables;
 
 /* OPP Config flags */
 #define OPP_CONFIG_CLK			BIT(0)
-- 
2.31.1.272.g89b43f80a514

[PATCH 2/2] OPP: Protect `lazy_opp_tables` list with `opp_table_lock`

[Viresh Kumar]

The `opp_table_lock` lock is already used to protect the list elsewhere,
use it while adding or removing entries from it.

Reported-by: Stephan Gerhold <stephan.gerhold@kernkonzept.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
Stephan: Can you please give this a try ?

 drivers/opp/of.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/opp/of.c b/drivers/opp/of.c
index c740a907ef76..ac2179d5da4c 100644
--- a/drivers/opp/of.c
+++ b/drivers/opp/of.c
@@ -21,7 +21,7 @@
 
 #include "opp.h"
 
-/* OPP tables with uninitialized required OPPs */
+/* OPP tables with uninitialized required OPPs, protected by opp_table_lock */
 static LIST_HEAD(lazy_opp_tables);
 
 /*
@@ -148,7 +148,10 @@ static void _opp_table_free_required_tables(struct opp_table *opp_table)
 
 	opp_table->required_opp_count = 0;
 	opp_table->required_opp_tables = NULL;
+
+	mutex_lock(&opp_table_lock);
 	list_del(&opp_table->lazy);
+	mutex_unlock(&opp_table_lock);
 }
 
 /*
@@ -197,8 +200,15 @@ static void _opp_table_alloc_required_tables(struct opp_table *opp_table,
 	}
 
 	/* Let's do the linking later on */
-	if (lazy)
+	if (lazy) {
+		/*
+		 * The OPP table is not held while allocating the table, take it
+		 * now to avoid corruption to the lazy_opp_tables list.
+		 */
+		mutex_lock(&opp_table_lock);
 		list_add(&opp_table->lazy, &lazy_opp_tables);
+		mutex_unlock(&opp_table_lock);
+	}
 	else
 		_update_set_required_opps(opp_table);
 
-- 
2.31.1.272.g89b43f80a514

Re: [PATCH 2/2] OPP: Protect `lazy_opp_tables` list with `opp_table_lock`

[Stephan Gerhold]

On Thu, Jun 08, 2023 at 01:13:23PM +0530, Viresh Kumar wrote:
> The `opp_table_lock` lock is already used to protect the list elsewhere,
> use it while adding or removing entries from it.
> 
> Reported-by: Stephan Gerhold <stephan.gerhold@kernkonzept.com>
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
> ---
> Stephan: Can you please give this a try ?

Thanks, works fine for me. (Note that I don't have any races or
corruption without this patch either so the testing result might
not mean too much.) The patch also looks good!

Tested-by: Stephan Gerhold <stephan.gerhold@kernkonzept.com>

> 
>  drivers/opp/of.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/opp/of.c b/drivers/opp/of.c
> index c740a907ef76..ac2179d5da4c 100644
> --- a/drivers/opp/of.c
> +++ b/drivers/opp/of.c
> @@ -21,7 +21,7 @@
>  
>  #include "opp.h"
>  
> -/* OPP tables with uninitialized required OPPs */
> +/* OPP tables with uninitialized required OPPs, protected by opp_table_lock */
>  static LIST_HEAD(lazy_opp_tables);
>  
>  /*
> @@ -148,7 +148,10 @@ static void _opp_table_free_required_tables(struct opp_table *opp_table)
>  
>  	opp_table->required_opp_count = 0;
>  	opp_table->required_opp_tables = NULL;
> +
> +	mutex_lock(&opp_table_lock);
>  	list_del(&opp_table->lazy);
> +	mutex_unlock(&opp_table_lock);
>  }
>  
>  /*
> @@ -197,8 +200,15 @@ static void _opp_table_alloc_required_tables(struct opp_table *opp_table,
>  	}
>  
>  	/* Let's do the linking later on */
> -	if (lazy)
> +	if (lazy) {
> +		/*
> +		 * The OPP table is not held while allocating the table, take it
> +		 * now to avoid corruption to the lazy_opp_tables list.
> +		 */
> +		mutex_lock(&opp_table_lock);
>  		list_add(&opp_table->lazy, &lazy_opp_tables);
> +		mutex_unlock(&opp_table_lock);
> +	}
>  	else
>  		_update_set_required_opps(opp_table);
>  
> -- 
> 2.31.1.272.g89b43f80a514
> 

-- 
Stephan Gerhold
Kernkonzept GmbH at Dresden, Germany, HRB 31129, CEO Dr.-Ing. Michael Hohmuth