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/******************************************************
The thread local storage
(c) 1995 Innobase Oy
Created 10/5/1995 Heikki Tuuri
*******************************************************/
#include "thr0loc.h"
#ifdef UNIV_NONINL
#include "thr0loc.ic"
#endif
#include "sync0sync.h"
#include "hash0hash.h"
#include "mem0mem.h"
#include "srv0srv.h"
/*
IMPLEMENTATION OF THREAD LOCAL STORAGE
======================================
The threads sometimes need private data which depends on the thread id.
This is implemented as a hash table, where the hash value is calculated
from the thread id, to prepare for a large number of threads. The hash table
is protected by a mutex. If you need modify the program and put new data to
the thread local storage, just add it to struct thr_local_struct in the
header file. */
/* Mutex protecting the local storage hash table */
mutex_t thr_local_mutex;
/* The hash table. The module is not yet initialized when it is NULL. */
hash_table_t* thr_local_hash = NULL;
/* The private data for each thread should be put to
the structure below and the accessor functions written
for the field. */
typedef struct thr_local_struct thr_local_t;
struct thr_local_struct{
os_thread_id_t id; /* id of the thread which owns this struct */
os_thread_t handle; /* operating system handle to the thread */
ulint slot_no;/* the index of the slot in the thread table
for this thread */
ibool in_ibuf;/* TRUE if the the thread is doing an ibuf
operation */
hash_node_t hash; /* hash chain node */
ulint magic_n;
};
#define THR_LOCAL_MAGIC_N 1231234
/***********************************************************************
Returns the local storage struct for a thread. */
static
thr_local_t*
thr_local_get(
/*==========*/
/* out: local storage */
os_thread_id_t id) /* in: thread id of the thread */
{
thr_local_t* local;
try_again:
ut_ad(thr_local_hash);
#ifdef UNIV_SYNC_DEBUG
ut_ad(mutex_own(&thr_local_mutex));
#endif /* UNIV_SYNC_DEBUG */
/* Look for the local struct in the hash table */
local = NULL;
HASH_SEARCH(hash, thr_local_hash, os_thread_pf(id),
local, os_thread_eq(local->id, id));
if (local == NULL) {
mutex_exit(&thr_local_mutex);
thr_local_create();
mutex_enter(&thr_local_mutex);
goto try_again;
}
ut_ad(local->magic_n == THR_LOCAL_MAGIC_N);
return(local);
}
/***********************************************************************
Gets the slot number in the thread table of a thread. */
ulint
thr_local_get_slot_no(
/*==================*/
/* out: slot number */
os_thread_id_t id) /* in: thread id of the thread */
{
ulint slot_no;
thr_local_t* local;
mutex_enter(&thr_local_mutex);
local = thr_local_get(id);
slot_no = local->slot_no;
mutex_exit(&thr_local_mutex);
return(slot_no);
}
/***********************************************************************
Sets the slot number in the thread table of a thread. */
void
thr_local_set_slot_no(
/*==================*/
os_thread_id_t id, /* in: thread id of the thread */
ulint slot_no)/* in: slot number */
{
thr_local_t* local;
mutex_enter(&thr_local_mutex);
local = thr_local_get(id);
local->slot_no = slot_no;
mutex_exit(&thr_local_mutex);
}
/***********************************************************************
Returns pointer to the 'in_ibuf' field within the current thread local
storage. */
ibool*
thr_local_get_in_ibuf_field(void)
/*=============================*/
/* out: pointer to the in_ibuf field */
{
thr_local_t* local;
mutex_enter(&thr_local_mutex);
local = thr_local_get(os_thread_get_curr_id());
mutex_exit(&thr_local_mutex);
return(&(local->in_ibuf));
}
/***********************************************************************
Creates a local storage struct for the calling new thread. */
void
thr_local_create(void)
/*==================*/
{
thr_local_t* local;
if (thr_local_hash == NULL) {
thr_local_init();
}
local = mem_alloc(sizeof(thr_local_t));
local->id = os_thread_get_curr_id();
local->handle = os_thread_get_curr();
local->magic_n = THR_LOCAL_MAGIC_N;
local->in_ibuf = FALSE;
mutex_enter(&thr_local_mutex);
HASH_INSERT(thr_local_t, hash, thr_local_hash,
os_thread_pf(os_thread_get_curr_id()),
local);
mutex_exit(&thr_local_mutex);
}
/***********************************************************************
Frees the local storage struct for the specified thread. */
void
thr_local_free(
/*===========*/
os_thread_id_t id) /* in: thread id */
{
thr_local_t* local;
mutex_enter(&thr_local_mutex);
/* Look for the local struct in the hash table */
HASH_SEARCH(hash, thr_local_hash, os_thread_pf(id),
local, os_thread_eq(local->id, id));
if (local == NULL) {
mutex_exit(&thr_local_mutex);
return;
}
HASH_DELETE(thr_local_t, hash, thr_local_hash,
os_thread_pf(id), local);
mutex_exit(&thr_local_mutex);
ut_a(local->magic_n == THR_LOCAL_MAGIC_N);
mem_free(local);
}
/********************************************************************
Initializes the thread local storage module. */
void
thr_local_init(void)
/*================*/
{
ut_a(thr_local_hash == NULL);
thr_local_hash = hash_create(OS_THREAD_MAX_N + 100);
mutex_create(&thr_local_mutex);
mutex_set_level(&thr_local_mutex, SYNC_THR_LOCAL);
}
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