From mboxrd@z Thu Jan  1 00:00:00 1970
From: mike@android.com (Mike Chan)
Date: Tue, 9 Mar 2010 16:11:52 -0800
Subject: [PATCH] omap: resource: Add per-resource mutex for OMAP resource
	framework
In-Reply-To: <-1645286213079228429@unknownmsgid>
References: <-1645286213079228429@unknownmsgid>
Message-ID: <8bb80c381003091611l7211439ief40c5cf31e782a0@mail.gmail.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Tue, Mar 9, 2010 at 4:09 PM,  <y@google.com> wrote:
> From: Chunqiu Wang <cqwang@motorola.com>
>
> Current OMAP resource fwk uses a global res_mutex
> for resource_request and resource_release calls
> for all the available resources.It may cause dead
> lock if resource_request/resource_release is called
> recursively.
>
> For current OMAP3 VDD1/VDD2 resource, the change_level
> implementation is mach-omap2/resource34xx.c/set_opp(),
> when using resource_release to remove vdd1 constraint,
> this function may call resource_release again to release
> Vdd2 constrait if target vdd1 level is less than OPP3.
> in this scenario, the global res_mutex down operation
> will be called again, this will cause the second
> down operation hang there.
>
> To fix the problem, per-resource mutex is added
> to avoid hangup when resource_request/resource_release
> is called recursively.
>
> Signed-off-by: Chunqiu Wang <cqwang@motorola.com>
> Signed-off-by: Mike Chan <mike@android.com>
> ---
> ?arch/arm/plat-omap/include/plat/resource.h | ? ?2 ++
> ?arch/arm/plat-omap/resource.c ? ? ? ? ? ? ?| ? 21 ++++++++++-----------
> ?2 files changed, 12 insertions(+), 11 deletions(-)
>
> diff --git a/arch/arm/plat-omap/include/plat/resource.h b/arch/arm/plat-omap/include/plat/resource.h
> index 9acebcc..b5aff1f 100644
> --- a/arch/arm/plat-omap/include/plat/resource.h
> +++ b/arch/arm/plat-omap/include/plat/resource.h
> @@ -54,6 +54,8 @@ struct shared_resource {
> ? ? ? ?/* Shared resource operations */
> ? ? ? ?struct shared_resource_ops *ops;
> ? ? ? ?struct list_head node;
> + ? ? ? /* Protect each resource */
> + ? ? ? struct mutex resource_mutex;
> ?};
>
> ?struct shared_resource_ops {
> diff --git a/arch/arm/plat-omap/resource.c b/arch/arm/plat-omap/resource.c
> index f1cdecf..0a7b79b 100644
> --- a/arch/arm/plat-omap/resource.c
> +++ b/arch/arm/plat-omap/resource.c
> @@ -277,6 +277,7 @@ int resource_register(struct shared_resource *resp)
> ? ? ? ?}
>
> ? ? ? ?INIT_LIST_HEAD(&resp->users_list);
> + ? ? ? mutex_init(&resp->resource_mutex);
>
> ? ? ? ?/* Add the resource to the resource list */
> ? ? ? ?list_add(&resp->node, &res_list);
> @@ -339,14 +340,13 @@ int resource_request(const char *name, struct device *dev,
> ? ? ? ?struct ?users_list *user;
> ? ? ? ?int ? ? found = 0, ret = 0;
>
> - ? ? ? down(&res_mutex);
> - ? ? ? resp = _resource_lookup(name);
> + ? ? ? resp = resource_lookup(name);
> ? ? ? ?if (!resp) {
> ? ? ? ? ? ? ? ?printk(KERN_ERR "resource_request: Invalid resource name\n");
> - ? ? ? ? ? ? ? ret = -EINVAL;
> - ? ? ? ? ? ? ? goto res_unlock;
> + ? ? ? ? ? ? ? return -EINVAL;
> ? ? ? ?}
>
> + ? ? ? mutex_lock(&resp->resource_mutex);
> ? ? ? ?/* Call the resource specific validate function */
> ? ? ? ?if (resp->ops->validate_level) {
> ? ? ? ? ? ? ? ?ret = resp->ops->validate_level(resp, level);
> @@ -375,7 +375,7 @@ int resource_request(const char *name, struct device *dev,
> ? ? ? ?user->level = level;
>
> ?res_unlock:
> - ? ? ? up(&res_mutex);
> + ? ? ? mutex_unlock(&resp->resource_mutex);
> ? ? ? ?/*
> ? ? ? ? * Recompute and set the current level for the resource.
> ? ? ? ? * NOTE: update_resource level moved out of spin_lock, as it may call
> @@ -406,14 +406,13 @@ int resource_release(const char *name, struct device *dev)
> ? ? ? ?struct users_list *user;
> ? ? ? ?int found = 0, ret = 0;
>
> - ? ? ? down(&res_mutex);
> - ? ? ? resp = _resource_lookup(name);
> + ? ? ? resp = resource_lookup(name);
> ? ? ? ?if (!resp) {
> ? ? ? ? ? ? ? ?printk(KERN_ERR "resource_release: Invalid resource name\n");
> - ? ? ? ? ? ? ? ret = -EINVAL;
> - ? ? ? ? ? ? ? goto res_unlock;
> + ? ? ? ? ? ? ? return -EINVAL;
> ? ? ? ?}
>
> + ? ? ? mutex_lock(&resp->resource_mutex);
> ? ? ? ?list_for_each_entry(user, &resp->users_list, node) {
> ? ? ? ? ? ? ? ?if (user->dev == dev) {
> ? ? ? ? ? ? ? ? ? ? ? ?found = 1;
> @@ -434,7 +433,7 @@ int resource_release(const char *name, struct device *dev)
> ? ? ? ?/* Recompute and set the current level for the resource */
> ? ? ? ?ret = update_resource_level(resp);
> ?res_unlock:
> - ? ? ? up(&res_mutex);
> + ? ? ? mutex_unlock(&resp->resource_mutex);
> ? ? ? ?return ret;
> ?}
> ?EXPORT_SYMBOL(resource_release);
> @@ -458,7 +457,7 @@ int resource_get_level(const char *name)
> ? ? ? ? ? ? ? ?up(&res_mutex);
> ? ? ? ? ? ? ? ?return -EINVAL;
> ? ? ? ?}
> - ? ? ? ret = resp->curr_level;
> + ? ? ? ret = ?resp->curr_level;
> ? ? ? ?up(&res_mutex);
> ? ? ? ?return ret;
> ?}
> --
> 1.6.6.2
>
>

Oops, my git client was slightly screwed up, apologies, I meant to
send this from mike at android.com, the patch is still good though :)

-- Mike