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[RFC v2 6/7] tracepoint: use new hashtable implementation

 

 

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levinsasha928 at gmail

Aug 3, 2012, 7:23 AM

Post #1 of 5 (134 views)
Permalink
[RFC v2 6/7] tracepoint: use new hashtable implementation

Switch tracepoints to use the new hashtable implementation. This reduces the amount of
generic unrelated code in the tracepoints.

Signed-off-by: Sasha Levin <levinsasha928 [at] gmail>
---
kernel/tracepoint.c | 26 +++++++++-----------------
1 files changed, 9 insertions(+), 17 deletions(-)

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index d96ba22..b5a2650 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -26,6 +26,7 @@
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/static_key.h>
+#include <linux/hashtable.h>

extern struct tracepoint * const __start___tracepoints_ptrs[];
extern struct tracepoint * const __stop___tracepoints_ptrs[];
@@ -49,8 +50,7 @@ static LIST_HEAD(tracepoint_module_list);
* Protected by tracepoints_mutex.
*/
#define TRACEPOINT_HASH_BITS 6
-#define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
-static struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
+DEFINE_STATIC_HASHTABLE(tracepoint_table, TRACEPOINT_HASH_BITS);

/*
* Note about RCU :
@@ -191,16 +191,14 @@ tracepoint_entry_remove_probe(struct tracepoint_entry *entry,
*/
static struct tracepoint_entry *get_tracepoint(const char *name)
{
- struct hlist_head *head;
struct hlist_node *node;
struct tracepoint_entry *e;
u32 hash = jhash(name, strlen(name), 0);

- head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
- hlist_for_each_entry(e, node, head, hlist) {
+ hash_for_each_possible(&tracepoint_table, node, e, hlist, hash)
if (!strcmp(name, e->name))
return e;
- }
+
return NULL;
}

@@ -210,19 +208,13 @@ static struct tracepoint_entry *get_tracepoint(const char *name)
*/
static struct tracepoint_entry *add_tracepoint(const char *name)
{
- struct hlist_head *head;
- struct hlist_node *node;
struct tracepoint_entry *e;
size_t name_len = strlen(name) + 1;
u32 hash = jhash(name, name_len-1, 0);

- head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
- hlist_for_each_entry(e, node, head, hlist) {
- if (!strcmp(name, e->name)) {
- printk(KERN_NOTICE
- "tracepoint %s busy\n", name);
- return ERR_PTR(-EEXIST); /* Already there */
- }
+ if (get_tracepoint(name)) {
+ printk(KERN_NOTICE "tracepoint %s busy\n", name);
+ return ERR_PTR(-EEXIST); /* Already there */
}
/*
* Using kmalloc here to allocate a variable length element. Could
@@ -234,7 +226,7 @@ static struct tracepoint_entry *add_tracepoint(const char *name)
memcpy(&e->name[0], name, name_len);
e->funcs = NULL;
e->refcount = 0;
- hlist_add_head(&e->hlist, head);
+ hash_add(&tracepoint_table, &e->hlist, hash);
return e;
}

@@ -244,7 +236,7 @@ static struct tracepoint_entry *add_tracepoint(const char *name)
*/
static inline void remove_tracepoint(struct tracepoint_entry *e)
{
- hlist_del(&e->hlist);
+ hash_del(&e->hlist);
kfree(e);
}

--
1.7.8.6

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rostedt at goodmis

Aug 4, 2012, 5:36 PM

Post #2 of 5 (121 views)
Permalink
Re: [RFC v2 6/7] tracepoint: use new hashtable implementation [In reply to]

FYI, Mathieu is the author of this file.

-- Steve


On Fri, 2012-08-03 at 16:23 +0200, Sasha Levin wrote:
> Switch tracepoints to use the new hashtable implementation. This reduces the amount of
> generic unrelated code in the tracepoints.
>
> Signed-off-by: Sasha Levin <levinsasha928 [at] gmail>
> ---
> kernel/tracepoint.c | 26 +++++++++-----------------
> 1 files changed, 9 insertions(+), 17 deletions(-)
>
> diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
> index d96ba22..b5a2650 100644
> --- a/kernel/tracepoint.c
> +++ b/kernel/tracepoint.c
> @@ -26,6 +26,7 @@
> #include <linux/slab.h>
> #include <linux/sched.h>
> #include <linux/static_key.h>
> +#include <linux/hashtable.h>
>
> extern struct tracepoint * const __start___tracepoints_ptrs[];
> extern struct tracepoint * const __stop___tracepoints_ptrs[];
> @@ -49,8 +50,7 @@ static LIST_HEAD(tracepoint_module_list);
> * Protected by tracepoints_mutex.
> */
> #define TRACEPOINT_HASH_BITS 6
> -#define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
> -static struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
> +DEFINE_STATIC_HASHTABLE(tracepoint_table, TRACEPOINT_HASH_BITS);
>
> /*
> * Note about RCU :
> @@ -191,16 +191,14 @@ tracepoint_entry_remove_probe(struct tracepoint_entry *entry,
> */
> static struct tracepoint_entry *get_tracepoint(const char *name)
> {
> - struct hlist_head *head;
> struct hlist_node *node;
> struct tracepoint_entry *e;
> u32 hash = jhash(name, strlen(name), 0);
>
> - head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
> - hlist_for_each_entry(e, node, head, hlist) {
> + hash_for_each_possible(&tracepoint_table, node, e, hlist, hash)
> if (!strcmp(name, e->name))
> return e;
> - }
> +
> return NULL;
> }
>
> @@ -210,19 +208,13 @@ static struct tracepoint_entry *get_tracepoint(const char *name)
> */
> static struct tracepoint_entry *add_tracepoint(const char *name)
> {
> - struct hlist_head *head;
> - struct hlist_node *node;
> struct tracepoint_entry *e;
> size_t name_len = strlen(name) + 1;
> u32 hash = jhash(name, name_len-1, 0);
>
> - head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
> - hlist_for_each_entry(e, node, head, hlist) {
> - if (!strcmp(name, e->name)) {
> - printk(KERN_NOTICE
> - "tracepoint %s busy\n", name);
> - return ERR_PTR(-EEXIST); /* Already there */
> - }
> + if (get_tracepoint(name)) {
> + printk(KERN_NOTICE "tracepoint %s busy\n", name);
> + return ERR_PTR(-EEXIST); /* Already there */
> }
> /*
> * Using kmalloc here to allocate a variable length element. Could
> @@ -234,7 +226,7 @@ static struct tracepoint_entry *add_tracepoint(const char *name)
> memcpy(&e->name[0], name, name_len);
> e->funcs = NULL;
> e->refcount = 0;
> - hlist_add_head(&e->hlist, head);
> + hash_add(&tracepoint_table, &e->hlist, hash);
> return e;
> }
>
> @@ -244,7 +236,7 @@ static struct tracepoint_entry *add_tracepoint(const char *name)
> */
> static inline void remove_tracepoint(struct tracepoint_entry *e)
> {
> - hlist_del(&e->hlist);
> + hash_del(&e->hlist);
> kfree(e);
> }
>


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mathieu.desnoyers at efficios

Aug 5, 2012, 9:31 AM

Post #3 of 5 (114 views)
Permalink
Re: [RFC v2 6/7] tracepoint: use new hashtable implementation [In reply to]

* Steven Rostedt (rostedt [at] goodmis) wrote:
> FYI, Mathieu is the author of this file.
>
> -- Steve
>
>
> On Fri, 2012-08-03 at 16:23 +0200, Sasha Levin wrote:
> > Switch tracepoints to use the new hashtable implementation. This reduces the amount of
> > generic unrelated code in the tracepoints.
> >
> > Signed-off-by: Sasha Levin <levinsasha928 [at] gmail>
> > ---
> > kernel/tracepoint.c | 26 +++++++++-----------------
> > 1 files changed, 9 insertions(+), 17 deletions(-)
> >
> > diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
> > index d96ba22..b5a2650 100644
> > --- a/kernel/tracepoint.c
> > +++ b/kernel/tracepoint.c
> > @@ -26,6 +26,7 @@
> > #include <linux/slab.h>
> > #include <linux/sched.h>
> > #include <linux/static_key.h>
> > +#include <linux/hashtable.h>
> >
> > extern struct tracepoint * const __start___tracepoints_ptrs[];
> > extern struct tracepoint * const __stop___tracepoints_ptrs[];
> > @@ -49,8 +50,7 @@ static LIST_HEAD(tracepoint_module_list);
> > * Protected by tracepoints_mutex.
> > */
> > #define TRACEPOINT_HASH_BITS 6
> > -#define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
> > -static struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
> > +DEFINE_STATIC_HASHTABLE(tracepoint_table, TRACEPOINT_HASH_BITS);

I wonder why the "static" has been embedded within
"DEFINE_STATIC_HASHTABLE" ? I'm used to see something similar to:

static DEFINE_HASHTABLE(tracepoint_table, TRACEPOINT_HASH_BITS);

elsewhere in the kernel (e.g. static DEFINE_PER_CPU(), static
DEFINE_MUTEX(), etc).

> >
> > /*
> > * Note about RCU :
> > @@ -191,16 +191,14 @@ tracepoint_entry_remove_probe(struct tracepoint_entry *entry,
> > */
> > static struct tracepoint_entry *get_tracepoint(const char *name)
> > {
> > - struct hlist_head *head;
> > struct hlist_node *node;
> > struct tracepoint_entry *e;
> > u32 hash = jhash(name, strlen(name), 0);
> >
> > - head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
> > - hlist_for_each_entry(e, node, head, hlist) {
> > + hash_for_each_possible(&tracepoint_table, node, e, hlist, hash)
> > if (!strcmp(name, e->name))
> > return e;
> > - }
> > +

Typically, where there are 2 or more nesting levels, I try to keep the
outer brackets, even if the 1st level only contain a single statement
(this is what I did across tracepoint.c). This is especially useful when
nesting multiple if levels, and ensures the "else" clause match the
right if. We might want to keep it that way within the file, to ensure
style consistency.

Other than that, it looks good!

Thanks!

Mathieu

> > return NULL;
> > }
> >
> > @@ -210,19 +208,13 @@ static struct tracepoint_entry *get_tracepoint(const char *name)
> > */
> > static struct tracepoint_entry *add_tracepoint(const char *name)
> > {
> > - struct hlist_head *head;
> > - struct hlist_node *node;
> > struct tracepoint_entry *e;
> > size_t name_len = strlen(name) + 1;
> > u32 hash = jhash(name, name_len-1, 0);
> >
> > - head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
> > - hlist_for_each_entry(e, node, head, hlist) {
> > - if (!strcmp(name, e->name)) {
> > - printk(KERN_NOTICE
> > - "tracepoint %s busy\n", name);
> > - return ERR_PTR(-EEXIST); /* Already there */
> > - }
> > + if (get_tracepoint(name)) {
> > + printk(KERN_NOTICE "tracepoint %s busy\n", name);
> > + return ERR_PTR(-EEXIST); /* Already there */
> > }
> > /*
> > * Using kmalloc here to allocate a variable length element. Could
> > @@ -234,7 +226,7 @@ static struct tracepoint_entry *add_tracepoint(const char *name)
> > memcpy(&e->name[0], name, name_len);
> > e->funcs = NULL;
> > e->refcount = 0;
> > - hlist_add_head(&e->hlist, head);
> > + hash_add(&tracepoint_table, &e->hlist, hash);
> > return e;
> > }
> >
> > @@ -244,7 +236,7 @@ static struct tracepoint_entry *add_tracepoint(const char *name)
> > */
> > static inline void remove_tracepoint(struct tracepoint_entry *e)
> > {
> > - hlist_del(&e->hlist);
> > + hash_del(&e->hlist);
> > kfree(e);
> > }
> >
>
>

--
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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levinsasha928 at gmail

Aug 5, 2012, 10:03 AM

Post #4 of 5 (116 views)
Permalink
Re: [RFC v2 6/7] tracepoint: use new hashtable implementation [In reply to]

On 08/05/2012 06:31 PM, Mathieu Desnoyers wrote:
> * Steven Rostedt (rostedt [at] goodmis) wrote:
>> FYI, Mathieu is the author of this file.
>>
>> -- Steve
>>
>>
>> On Fri, 2012-08-03 at 16:23 +0200, Sasha Levin wrote:
>>> Switch tracepoints to use the new hashtable implementation. This reduces the amount of
>>> generic unrelated code in the tracepoints.
>>>
>>> Signed-off-by: Sasha Levin <levinsasha928 [at] gmail>
>>> ---
>>> kernel/tracepoint.c | 26 +++++++++-----------------
>>> 1 files changed, 9 insertions(+), 17 deletions(-)
>>>
>>> diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
>>> index d96ba22..b5a2650 100644
>>> --- a/kernel/tracepoint.c
>>> +++ b/kernel/tracepoint.c
>>> @@ -26,6 +26,7 @@
>>> #include <linux/slab.h>
>>> #include <linux/sched.h>
>>> #include <linux/static_key.h>
>>> +#include <linux/hashtable.h>
>>>
>>> extern struct tracepoint * const __start___tracepoints_ptrs[];
>>> extern struct tracepoint * const __stop___tracepoints_ptrs[];
>>> @@ -49,8 +50,7 @@ static LIST_HEAD(tracepoint_module_list);
>>> * Protected by tracepoints_mutex.
>>> */
>>> #define TRACEPOINT_HASH_BITS 6
>>> -#define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
>>> -static struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
>>> +DEFINE_STATIC_HASHTABLE(tracepoint_table, TRACEPOINT_HASH_BITS);
>
> I wonder why the "static" has been embedded within
> "DEFINE_STATIC_HASHTABLE" ? I'm used to see something similar to:
>
> static DEFINE_HASHTABLE(tracepoint_table, TRACEPOINT_HASH_BITS);
>
> elsewhere in the kernel (e.g. static DEFINE_PER_CPU(), static
> DEFINE_MUTEX(), etc).

We had to create two different definitions of hashtable, one to be used as static and one to be used in structs. I chose the uglier way of doing it, and Tejun already pointed it out :)

It will be much nicer in the future.

>>>
>>> /*
>>> * Note about RCU :
>>> @@ -191,16 +191,14 @@ tracepoint_entry_remove_probe(struct tracepoint_entry *entry,
>>> */
>>> static struct tracepoint_entry *get_tracepoint(const char *name)
>>> {
>>> - struct hlist_head *head;
>>> struct hlist_node *node;
>>> struct tracepoint_entry *e;
>>> u32 hash = jhash(name, strlen(name), 0);
>>>
>>> - head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
>>> - hlist_for_each_entry(e, node, head, hlist) {
>>> + hash_for_each_possible(&tracepoint_table, node, e, hlist, hash)
>>> if (!strcmp(name, e->name))
>>> return e;
>>> - }
>>> +
>
> Typically, where there are 2 or more nesting levels, I try to keep the
> outer brackets, even if the 1st level only contain a single statement
> (this is what I did across tracepoint.c). This is especially useful when
> nesting multiple if levels, and ensures the "else" clause match the
> right if. We might want to keep it that way within the file, to ensure
> style consistency.

Roger that, will fix.

> Other than that, it looks good!
>
> Thanks!
>
> Mathieu
>

Thanks for the review Mathieu!

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mathieu.desnoyers at efficios

Aug 5, 2012, 10:12 AM

Post #5 of 5 (120 views)
Permalink
Re: [RFC v2 6/7] tracepoint: use new hashtable implementation [In reply to]

* Sasha Levin (levinsasha928 [at] gmail) wrote:
[...]
> > Other than that, it looks good!
> >
> > Thanks!
> >
> > Mathieu
> >
>
> Thanks for the review Mathieu!

No problem! By the way, if you want to have a look at another hash table
API for ideas, here is the RCU lock-free hash table API, within the
Userspace RCU tree:

from git://git.lttng.org/userspace-rcu.git
branch: master
API: urcu/rculfhash.h
core code: rculfhash.c
hash table index memory management:
rculfhash-mm-chunk.c, rculfhash-mm-mmap.c, rculfhash-mm-order.c

The git tree is down today due to electrical maintenance, so I am
appending the hash table API below.


#ifndef _URCU_RCULFHASH_H
#define _URCU_RCULFHASH_H

/*
* urcu/rculfhash.h
*
* Userspace RCU library - Lock-Free RCU Hash Table
*
* Copyright 2011 - Mathieu Desnoyers <mathieu.desnoyers [at] efficios>
* Copyright 2011 - Lai Jiangshan <laijs [at] cn>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
* Include this file _after_ including your URCU flavor.
*/

#include <stdint.h>
#include <urcu/compiler.h>
#include <urcu-call-rcu.h>
#include <urcu-flavor.h>

#ifdef __cplusplus
extern "C" {
#endif

/*
* cds_lfht_node: Contains the next pointers and reverse-hash
* value required for lookup and traversal of the hash table.
*
* struct cds_lfht_node should be aligned on 8-bytes boundaries because
* the three lower bits are used as flags. It is worth noting that the
* information contained within these three bits could be represented on
* two bits by re-using the same bit for REMOVAL_OWNER_FLAG and
* BUCKET_FLAG. This can be done if we ensure that no iterator nor
* updater check the BUCKET_FLAG after it detects that the REMOVED_FLAG
* is set. Given the minimum size of struct cds_lfht_node is 8 bytes on
* 32-bit architectures, we choose to go for simplicity and reserve
* three bits.
*
* struct cds_lfht_node can be embedded into a structure (as a field).
* caa_container_of() can be used to get the structure from the struct
* cds_lfht_node after a lookup.
*
* The structure which embeds it typically holds the key (or key-value
* pair) of the object. The caller code is responsible for calculation
* of the hash value for cds_lfht APIs.
*/
struct cds_lfht_node {
struct cds_lfht_node *next; /* ptr | REMOVAL_OWNER_FLAG | BUCKET_FLAG | REMOVED_FLAG */
unsigned long reverse_hash;
} __attribute__((aligned(8)));

/* cds_lfht_iter: Used to track state while traversing a hash chain. */
struct cds_lfht_iter {
struct cds_lfht_node *node, *next;
};

static inline
struct cds_lfht_node *cds_lfht_iter_get_node(struct cds_lfht_iter *iter)
{
return iter->node;
}

struct cds_lfht;

/*
* Caution !
* Ensure reader and writer threads are registered as urcu readers.
*/

typedef int (*cds_lfht_match_fct)(struct cds_lfht_node *node, const void *key);

/*
* cds_lfht_node_init - initialize a hash table node
* @node: the node to initialize.
*
* This function is kept to be eventually used for debugging purposes
* (detection of memory corruption).
*/
static inline
void cds_lfht_node_init(struct cds_lfht_node *node)
{
}

/*
* Hash table creation flags.
*/
enum {
CDS_LFHT_AUTO_RESIZE = (1U << 0),
CDS_LFHT_ACCOUNTING = (1U << 1),
};

struct cds_lfht_mm_type {
struct cds_lfht *(*alloc_cds_lfht)(unsigned long min_nr_alloc_buckets,
unsigned long max_nr_buckets);
void (*alloc_bucket_table)(struct cds_lfht *ht, unsigned long order);
void (*free_bucket_table)(struct cds_lfht *ht, unsigned long order);
struct cds_lfht_node *(*bucket_at)(struct cds_lfht *ht,
unsigned long index);
};

extern const struct cds_lfht_mm_type cds_lfht_mm_order;
extern const struct cds_lfht_mm_type cds_lfht_mm_chunk;
extern const struct cds_lfht_mm_type cds_lfht_mm_mmap;

/*
* _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
*/
struct cds_lfht *_cds_lfht_new(unsigned long init_size,
unsigned long min_nr_alloc_buckets,
unsigned long max_nr_buckets,
int flags,
const struct cds_lfht_mm_type *mm,
const struct rcu_flavor_struct *flavor,
pthread_attr_t *attr);

/*
* cds_lfht_new - allocate a hash table.
* @init_size: number of buckets to allocate initially. Must be power of two.
* @min_nr_alloc_buckets: the minimum number of allocated buckets.
* (must be power of two)
* @max_nr_buckets: the maximum number of hash table buckets allowed.
* (must be power of two)
* @flags: hash table creation flags (can be combined with bitwise or: '|').
* 0: no flags.
* CDS_LFHT_AUTO_RESIZE: automatically resize hash table.
* CDS_LFHT_ACCOUNTING: count the number of node addition
* and removal in the table
* @attr: optional resize worker thread attributes. NULL for default.
*
* Return NULL on error.
* Note: the RCU flavor must be already included before the hash table header.
*
* The programmer is responsible for ensuring that resize operation has a
* priority equal to hash table updater threads. It should be performed by
* specifying the appropriate priority in the pthread "attr" argument, and,
* for CDS_LFHT_AUTO_RESIZE, by ensuring that call_rcu worker threads also have
* this priority level. Having lower priority for call_rcu and resize threads
* does not pose any correctness issue, but the resize operations could be
* starved by updates, thus leading to long hash table bucket chains.
* Threads calling cds_lfht_new are NOT required to be registered RCU
* read-side threads. It can be called very early. (e.g. before RCU is
* initialized)
*/
static inline
struct cds_lfht *cds_lfht_new(unsigned long init_size,
unsigned long min_nr_alloc_buckets,
unsigned long max_nr_buckets,
int flags,
pthread_attr_t *attr)
{
return _cds_lfht_new(init_size, min_nr_alloc_buckets, max_nr_buckets,
flags, NULL, &rcu_flavor, attr);
}

/*
* cds_lfht_destroy - destroy a hash table.
* @ht: the hash table to destroy.
* @attr: (output) resize worker thread attributes, as received by cds_lfht_new.
* The caller will typically want to free this pointer if dynamically
* allocated. The attr point can be NULL if the caller does not
* need to be informed of the value passed to cds_lfht_new().
*
* Return 0 on success, negative error value on error.
* Threads calling this API need to be registered RCU read-side threads.
*/
int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr);

/*
* cds_lfht_count_nodes - count the number of nodes in the hash table.
* @ht: the hash table.
* @split_count_before: sample the node count split-counter before traversal.
* @count: traverse the hash table, count the number of nodes observed.
* @split_count_after: sample the node count split-counter after traversal.
*
* Call with rcu_read_lock held.
* Threads calling this API need to be registered RCU read-side threads.
*/
void cds_lfht_count_nodes(struct cds_lfht *ht,
long *split_count_before,
unsigned long *count,
long *split_count_after);

/*
* cds_lfht_lookup - lookup a node by key.
* @ht: the hash table.
* @hash: the key hash.
* @match: the key match function.
* @key: the current node key.
* @iter: node, if found (output). *iter->node set to NULL if not found.
*
* Call with rcu_read_lock held.
* Threads calling this API need to be registered RCU read-side threads.
* This function acts as a rcu_dereference() to read the node pointer.
*/
void cds_lfht_lookup(struct cds_lfht *ht, unsigned long hash,
cds_lfht_match_fct match, const void *key,
struct cds_lfht_iter *iter);

/*
* cds_lfht_next_duplicate - get the next item with same key, after iterator.
* @ht: the hash table.
* @match: the key match function.
* @key: the current node key.
* @iter: input: current iterator.
* output: node, if found. *iter->node set to NULL if not found.
*
* Uses an iterator initialized by a lookup or traversal. Important: the
* iterator _needs_ to be initialized before calling
* cds_lfht_next_duplicate.
* Sets *iter-node to the following node with same key.
* Sets *iter->node to NULL if no following node exists with same key.
* RCU read-side lock must be held across cds_lfht_lookup and
* cds_lfht_next calls, and also between cds_lfht_next calls using the
* node returned by a previous cds_lfht_next.
* Call with rcu_read_lock held.
* Threads calling this API need to be registered RCU read-side threads.
* This function acts as a rcu_dereference() to read the node pointer.
*/
void cds_lfht_next_duplicate(struct cds_lfht *ht,
cds_lfht_match_fct match, const void *key,
struct cds_lfht_iter *iter);

/*
* cds_lfht_first - get the first node in the table.
* @ht: the hash table.
* @iter: First node, if exists (output). *iter->node set to NULL if not found.
*
* Output in "*iter". *iter->node set to NULL if table is empty.
* Call with rcu_read_lock held.
* Threads calling this API need to be registered RCU read-side threads.
* This function acts as a rcu_dereference() to read the node pointer.
*/
void cds_lfht_first(struct cds_lfht *ht, struct cds_lfht_iter *iter);

/*
* cds_lfht_next - get the next node in the table.
* @ht: the hash table.
* @iter: input: current iterator.
* output: next node, if exists. *iter->node set to NULL if not found.
*
* Input/Output in "*iter". *iter->node set to NULL if *iter was
* pointing to the last table node.
* Call with rcu_read_lock held.
* Threads calling this API need to be registered RCU read-side threads.
* This function acts as a rcu_dereference() to read the node pointer.
*/
void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter);

/*
* cds_lfht_add - add a node to the hash table.
* @ht: the hash table.
* @hash: the key hash.
* @node: the node to add.
*
* This function supports adding redundant keys into the table.
* Call with rcu_read_lock held.
* Threads calling this API need to be registered RCU read-side threads.
* This function issues a full memory barrier before and after its
* atomic commit.
*/
void cds_lfht_add(struct cds_lfht *ht, unsigned long hash,
struct cds_lfht_node *node);

/*
* cds_lfht_add_unique - add a node to hash table, if key is not present.
* @ht: the hash table.
* @hash: the node's hash.
* @match: the key match function.
* @key: the node's key.
* @node: the node to try adding.
*
* Return the node added upon success.
* Return the unique node already present upon failure. If
* cds_lfht_add_unique fails, the node passed as parameter should be
* freed by the caller. In this case, the caller does NOT need to wait
* for a grace period before freeing the node.
* Call with rcu_read_lock held.
* Threads calling this API need to be registered RCU read-side threads.
*
* The semantic of this function is that if only this function is used
* to add keys into the table, no duplicated keys should ever be
* observable in the table. The same guarantee apply for combination of
* add_unique and add_replace (see below).
*
* Upon success, this function issues a full memory barrier before and
* after its atomic commit. Upon failure, this function acts like a
* simple lookup operation: it acts as a rcu_dereference() to read the
* node pointer. The failure case does not guarantee any other memory
* barrier.
*/
struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
unsigned long hash,
cds_lfht_match_fct match,
const void *key,
struct cds_lfht_node *node);

/*
* cds_lfht_add_replace - replace or add a node within hash table.
* @ht: the hash table.
* @hash: the node's hash.
* @match: the key match function.
* @key: the node's key.
* @node: the node to add.
*
* Return the node replaced upon success. If no node matching the key
* was present, return NULL, which also means the operation succeeded.
* This replacement operation should never fail.
* Call with rcu_read_lock held.
* Threads calling this API need to be registered RCU read-side threads.
* After successful replacement, a grace period must be waited for before
* freeing the memory reserved for the returned node.
*
* The semantic of replacement vs lookups and traversals is the
* following: if lookups and traversals are performed between a key
* unique insertion and its removal, we guarantee that the lookups and
* traversals will always find exactly one instance of the key if it is
* replaced concurrently with the lookups.
*
* Providing this semantic allows us to ensure that replacement-only
* schemes will never generate duplicated keys. It also allows us to
* guarantee that a combination of add_replace and add_unique updates
* will never generate duplicated keys.
*
* This function issues a full memory barrier before and after its
* atomic commit.
*/
struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht,
unsigned long hash,
cds_lfht_match_fct match,
const void *key,
struct cds_lfht_node *node);

/*
* cds_lfht_replace - replace a node pointed to by iter within hash table.
* @ht: the hash table.
* @old_iter: the iterator position of the node to replace.
* @hash: the node's hash.
* @match: the key match function.
* @key: the node's key.
* @new_node: the new node to use as replacement.
*
* Return 0 if replacement is successful, negative value otherwise.
* Replacing a NULL old node or an already removed node will fail with
* -ENOENT.
* If the hash or value of the node to replace and the new node differ,
* this function returns -EINVAL without proceeding to the replacement.
* Old node can be looked up with cds_lfht_lookup and cds_lfht_next.
* RCU read-side lock must be held between lookup and replacement.
* Call with rcu_read_lock held.
* Threads calling this API need to be registered RCU read-side threads.
* After successful replacement, a grace period must be waited for before
* freeing the memory reserved for the old node (which can be accessed
* with cds_lfht_iter_get_node).
*
* The semantic of replacement vs lookups is the same as
* cds_lfht_add_replace().
*
* Upon success, this function issues a full memory barrier before and
* after its atomic commit. Upon failure, this function does not issue
* any memory barrier.
*/
int cds_lfht_replace(struct cds_lfht *ht,
struct cds_lfht_iter *old_iter,
unsigned long hash,
cds_lfht_match_fct match,
const void *key,
struct cds_lfht_node *new_node);

/*
* cds_lfht_del - remove node pointed to by iterator from hash table.
* @ht: the hash table.
* @node: the node to delete.
*
* Return 0 if the node is successfully removed, negative value
* otherwise.
* Deleting a NULL node or an already removed node will fail with a
* negative value.
* Node can be looked up with cds_lfht_lookup and cds_lfht_next,
* followed by use of cds_lfht_iter_get_node.
* RCU read-side lock must be held between lookup and removal.
* Call with rcu_read_lock held.
* Threads calling this API need to be registered RCU read-side threads.
* After successful removal, a grace period must be waited for before
* freeing the memory reserved for old node (which can be accessed with
* cds_lfht_iter_get_node).
* Upon success, this function issues a full memory barrier before and
* after its atomic commit. Upon failure, this function does not issue
* any memory barrier.
*/
int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_node *node);

/*
* cds_lfht_is_node_deleted - query whether a node is removed from hash table.
*
* Return non-zero if the node is deleted from the hash table, 0
* otherwise.
* Node can be looked up with cds_lfht_lookup and cds_lfht_next,
* followed by use of cds_lfht_iter_get_node.
* RCU read-side lock must be held between lookup and call to this
* function.
* Call with rcu_read_lock held.
* Threads calling this API need to be registered RCU read-side threads.
* This function does not issue any memory barrier.
*/
int cds_lfht_is_node_deleted(struct cds_lfht_node *node);

/*
* cds_lfht_resize - Force a hash table resize
* @ht: the hash table.
* @new_size: update to this hash table size.
*
* Threads calling this API need to be registered RCU read-side threads.
* This function does not (necessarily) issue memory barriers.
*/
void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size);

/*
* Note: it is safe to perform element removal (del), replacement, or
* any hash table update operation during any of the following hash
* table traversals.
* These functions act as rcu_dereference() to read the node pointers.
*/
#define cds_lfht_for_each(ht, iter, node) \
for (cds_lfht_first(ht, iter), \
node = cds_lfht_iter_get_node(iter); \
node != NULL; \
cds_lfht_next(ht, iter), \
node = cds_lfht_iter_get_node(iter))

#define cds_lfht_for_each_duplicate(ht, hash, match, key, iter, node) \
for (cds_lfht_lookup(ht, hash, match, key, iter), \
node = cds_lfht_iter_get_node(iter); \
node != NULL; \
cds_lfht_next_duplicate(ht, match, key, iter), \
node = cds_lfht_iter_get_node(iter))

#define cds_lfht_for_each_entry(ht, iter, pos, member) \
for (cds_lfht_first(ht, iter), \
pos = caa_container_of(cds_lfht_iter_get_node(iter), \
__typeof__(*(pos)), member); \
&(pos)->member != NULL; \
cds_lfht_next(ht, iter), \
pos = caa_container_of(cds_lfht_iter_get_node(iter), \
__typeof__(*(pos)), member))

#define cds_lfht_for_each_entry_duplicate(ht, hash, match, key, \
iter, pos, member) \
for (cds_lfht_lookup(ht, hash, match, key, iter), \
pos = caa_container_of(cds_lfht_iter_get_node(iter), \
__typeof__(*(pos)), member); \
&(pos)->member != NULL; \
cds_lfht_next_duplicate(ht, match, key, iter), \
pos = caa_container_of(cds_lfht_iter_get_node(iter), \
__typeof__(*(pos)), member))

#ifdef __cplusplus
}
#endif

#endif /* _URCU_RCULFHASH_H */




--
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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