Re: [PATCH 2/3] of: Support hashtable lookups for phandles

From: Rob Herring
Date: Mon May 09 2016 - 17:22:23 EST


On Mon, May 9, 2016 at 1:11 PM, Pantelis Antoniou
<pantelis.antoniou@xxxxxxxxxxxx> wrote:

Why this is needed goes here.

Any data on how much time the current code takes?

> Signed-off-by: Pantelis Antoniou <pantelis.antoniou@xxxxxxxxxxxx>
> ---
> drivers/of/base.c | 35 ++++++++++++++++++++++++++++++++---
> drivers/of/dynamic.c | 8 ++++++++
> drivers/of/of_private.h | 31 +++++++++++++++++++++++++++++++
> include/linux/of.h | 2 ++
> 4 files changed, 73 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 20bbc2f..770cb95 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -27,6 +27,7 @@
> #include <linux/slab.h>
> #include <linux/string.h>
> #include <linux/proc_fs.h>
> +#include <linux/rhashtable.h>
>
> #include "of_private.h"
>
> @@ -41,6 +42,16 @@ static const char *of_stdout_options;
>
> struct kset *of_kset;
>
> +const struct rhashtable_params of_phandle_ht_params = {
> + .key_offset = offsetof(struct device_node, phandle), /* base offset */
> + .key_len = sizeof(phandle),
> + .head_offset = offsetof(struct device_node, ht_node),
> + .automatic_shrinking = true,
> +};
> +
> +struct rhashtable of_phandle_ht;
> +bool of_phandle_ht_initialized;

Get rid of this and of_phandle_ht_available. It should always be initialized.

> +
> /*
> * Used to protect the of_aliases, to hold off addition of nodes to sysfs.
> * This mutex must be held whenever modifications are being made to the
> @@ -162,6 +173,12 @@ int __of_attach_node_post(struct device_node *np)
> struct property *pp;
> int rc;
>
> + if (of_phandle_ht_available()) {
> + rc = of_phandle_ht_insert(np);
> + WARN(rc, "insert to phandle hash fail @%s\n",
> + of_node_full_name(np));
> + }
> +
> if (!IS_ENABLED(CONFIG_SYSFS))
> return 0;
>
> @@ -194,6 +211,13 @@ void __init of_core_init(void)
> struct device_node *np;
> int ret;
>
> + ret = rhashtable_init(&of_phandle_ht, &of_phandle_ht_params);
> + if (ret) {
> + pr_warn("devicetree: Failed to initialize hashtable\n");
> + return;
> + }
> + of_phandle_ht_initialized = 1;
> +
> /* Create the kset, and register existing nodes */
> mutex_lock(&of_mutex);
> of_kset = kset_create_and_add("devicetree", NULL, firmware_kobj);
> @@ -1073,9 +1097,14 @@ struct device_node *of_find_node_by_phandle(phandle handle)
> return NULL;
>
> raw_spin_lock_irqsave(&devtree_lock, flags);
> - for_each_of_allnodes(np)
> - if (np->phandle == handle)
> - break;
> + /* when we're ready use the hash table */
> + if (of_phandle_ht_available() && !in_interrupt())
> + np = of_phandle_ht_lookup(handle);
> + else { /* fallback */
> + for_each_of_allnodes(np)
> + if (np->phandle == handle)
> + break;
> + }
> of_node_get(np);
> raw_spin_unlock_irqrestore(&devtree_lock, flags);
> return np;
> diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
> index eb31a55..bdebdf5 100644
> --- a/drivers/of/dynamic.c
> +++ b/drivers/of/dynamic.c
> @@ -11,6 +11,7 @@
> #include <linux/slab.h>
> #include <linux/string.h>
> #include <linux/proc_fs.h>
> +#include <linux/rhashtable.h>
>
> #include "of_private.h"
>
> @@ -44,6 +45,13 @@ EXPORT_SYMBOL(of_node_put);
> void __of_detach_node_post(struct device_node *np)
> {
> struct property *pp;
> + int rc;
> +
> + if (of_phandle_ht_available()) {
> + rc = of_phandle_ht_remove(np);
> + WARN(rc, "remove from phandle hash fail @%s\n",
> + of_node_full_name(np));

Can this really fail?

Rob