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344 lines (286 loc) · 8.29 KB
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/* Thread package.
This is intended to be usable independently from Python.
The implementation for system foobar is in a file thread_foobar.h
which is included by this file dependent on config settings.
Stuff shared by all thread_*.h files is collected here. */
#include "Python.h"
#ifndef DONT_HAVE_STDIO_H
#include <stdio.h>
#endif
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#else
#ifdef Py_DEBUG
extern char *getenv(const char *);
#endif
#endif
#ifdef __DGUX
#define _USING_POSIX4A_DRAFT6
#endif
#ifdef __sgi
#ifndef HAVE_PTHREAD_H /* XXX Need to check in configure.in */
#undef _POSIX_THREADS
#endif
#endif
#include "pythread.h"
#ifndef _POSIX_THREADS
#ifdef __sgi
#define SGI_THREADS
#endif
#ifdef HAVE_THREAD_H
#define SOLARIS_THREADS
#endif
#if defined(sun) && !defined(SOLARIS_THREADS)
#define SUN_LWP
#endif
#if defined(__MWERKS__) && !defined(__BEOS__)
#define _POSIX_THREADS
#endif
#endif /* _POSIX_THREADS */
#ifdef Py_DEBUG
static int thread_debug = 0;
#define dprintf(args) (void)((thread_debug & 1) && printf args)
#define d2printf(args) ((thread_debug & 8) && printf args)
#else
#define dprintf(args)
#define d2printf(args)
#endif
static int initialized;
static void PyThread__init_thread(void); /* Forward */
void PyThread_init_thread(void)
{
#ifdef Py_DEBUG
char *p = getenv("THREADDEBUG");
if (p) {
if (*p)
thread_debug = atoi(p);
else
thread_debug = 1;
}
#endif /* Py_DEBUG */
if (initialized)
return;
initialized = 1;
dprintf(("PyThread_init_thread called\n"));
PyThread__init_thread();
}
#ifdef SGI_THREADS
#include "thread_sgi.h"
#endif
#ifdef SOLARIS_THREADS
#include "thread_solaris.h"
#endif
#ifdef SUN_LWP
#include "thread_lwp.h"
#endif
#ifdef HAVE_PTH
#include "thread_pth.h"
#undef _POSIX_THREADS
#endif
#ifdef _POSIX_THREADS
#include "thread_pthread.h"
#endif
#ifdef C_THREADS
#include "thread_cthread.h"
#endif
#ifdef NT_THREADS
#include "thread_nt.h"
#endif
#ifdef OS2_THREADS
#include "thread_os2.h"
#endif
#ifdef BEOS_THREADS
#include "thread_beos.h"
#endif
#ifdef WINCE_THREADS
#include "thread_wince.h"
#endif
#ifdef PLAN9_THREADS
#include "thread_plan9.h"
#endif
#ifdef ATHEOS_THREADS
#include "thread_atheos.h"
#endif
/*
#ifdef FOOBAR_THREADS
#include "thread_foobar.h"
#endif
*/
#ifndef Py_HAVE_NATIVE_TLS
/* If the platform has not supplied a platform specific
TLS implementation, provide our own.
This code stolen from "thread_sgi.h", where it was the only
implementation of an existing Python TLS API.
*/
/* ------------------------------------------------------------------------
Per-thread data ("key") support.
Use PyThread_create_key() to create a new key. This is typically shared
across threads.
Use PyThread_set_key_value(thekey, value) to associate void* value with
thekey in the current thread. Each thread has a distinct mapping of thekey
to a void* value. Caution: if the current thread already has a mapping
for thekey, value is ignored.
Use PyThread_get_key_value(thekey) to retrieve the void* value associated
with thekey in the current thread. This returns NULL if no value is
associated with thekey in the current thread.
Use PyThread_delete_key_value(thekey) to forget the current thread's associated
value for thekey. PyThread_delete_key(thekey) forgets the values associated
with thekey across *all* threads.
While some of these functions have error-return values, none set any
Python exception.
None of the functions does memory management on behalf of the void* values.
You need to allocate and deallocate them yourself. If the void* values
happen to be PyObject*, these functions don't do refcount operations on
them either.
The GIL does not need to be held when calling these functions; they supply
their own locking. This isn't true of PyThread_create_key(), though (see
next paragraph).
There's a hidden assumption that PyThread_create_key() will be called before
any of the other functions are called. There's also a hidden assumption
that calls to PyThread_create_key() are serialized externally.
------------------------------------------------------------------------ */
/* A singly-linked list of struct key objects remembers all the key->value
* associations. File static keyhead heads the list. keymutex is used
* to enforce exclusion internally.
*/
struct key {
/* Next record in the list, or NULL if this is the last record. */
struct key *next;
/* The thread id, according to PyThread_get_thread_ident(). */
long id;
/* The key and its associated value. */
int key;
void *value;
};
static struct key *keyhead = NULL;
static PyThread_type_lock keymutex = NULL;
static int nkeys = 0; /* PyThread_create_key() hands out nkeys+1 next */
/* Internal helper.
* If the current thread has a mapping for key, the appropriate struct key*
* is returned. NB: value is ignored in this case!
* If there is no mapping for key in the current thread, then:
* If value is NULL, NULL is returned.
* Else a mapping of key to value is created for the current thread,
* and a pointer to a new struct key* is returned; except that if
* malloc() can't find room for a new struct key*, NULL is returned.
* So when value==NULL, this acts like a pure lookup routine, and when
* value!=NULL, this acts like dict.setdefault(), returning an existing
* mapping if one exists, else creating a new mapping.
*
* Caution: this used to be too clever, trying to hold keymutex only
* around the "p->next = keyhead; keyhead = p" pair. That allowed
* another thread to mutate the list, via key deletion, concurrent with
* find_key() crawling over the list. Hilarity ensued. For example, when
* the for-loop here does "p = p->next", p could end up pointing at a
* record that PyThread_delete_key_value() was concurrently free()'ing.
* That could lead to anything, from failing to find a key that exists, to
* segfaults. Now we lock the whole routine.
*/
static struct key *
find_key(int key, void *value)
{
struct key *p;
long id = PyThread_get_thread_ident();
PyThread_acquire_lock(keymutex, 1);
for (p = keyhead; p != NULL; p = p->next) {
if (p->id == id && p->key == key)
goto Done;
}
if (value == NULL) {
assert(p == NULL);
goto Done;
}
p = (struct key *)malloc(sizeof(struct key));
if (p != NULL) {
p->id = id;
p->key = key;
p->value = value;
p->next = keyhead;
keyhead = p;
}
Done:
PyThread_release_lock(keymutex);
return p;
}
/* Return a new key. This must be called before any other functions in
* this family, and callers must arrange to serialize calls to this
* function. No violations are detected.
*/
int
PyThread_create_key(void)
{
/* All parts of this function are wrong if it's called by multiple
* threads simultaneously.
*/
if (keymutex == NULL)
keymutex = PyThread_allocate_lock();
return ++nkeys;
}
/* Forget the associations for key across *all* threads. */
void
PyThread_delete_key(int key)
{
struct key *p, **q;
PyThread_acquire_lock(keymutex, 1);
q = &keyhead;
while ((p = *q) != NULL) {
if (p->key == key) {
*q = p->next;
free((void *)p);
/* NB This does *not* free p->value! */
}
else
q = &p->next;
}
PyThread_release_lock(keymutex);
}
/* Confusing: If the current thread has an association for key,
* value is ignored, and 0 is returned. Else an attempt is made to create
* an association of key to value for the current thread. 0 is returned
* if that succeeds, but -1 is returned if there's not enough memory
* to create the association. value must not be NULL.
*/
int
PyThread_set_key_value(int key, void *value)
{
struct key *p;
assert(value != NULL);
p = find_key(key, value);
if (p == NULL)
return -1;
else
return 0;
}
/* Retrieve the value associated with key in the current thread, or NULL
* if the current thread doesn't have an association for key.
*/
void *
PyThread_get_key_value(int key)
{
struct key *p = find_key(key, NULL);
if (p == NULL)
return NULL;
else
return p->value;
}
/* Forget the current thread's association for key, if any. */
void
PyThread_delete_key_value(int key)
{
long id = PyThread_get_thread_ident();
struct key *p, **q;
PyThread_acquire_lock(keymutex, 1);
q = &keyhead;
while ((p = *q) != NULL) {
if (p->key == key && p->id == id) {
*q = p->next;
free((void *)p);
/* NB This does *not* free p->value! */
break;
}
else
q = &p->next;
}
PyThread_release_lock(keymutex);
}
#endif /* Py_HAVE_NATIVE_TLS */
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