mirror of
https://github.com/python/cpython
synced 2024-09-05 16:38:56 +00:00
355 lines
8.8 KiB
C
355 lines
8.8 KiB
C
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/* Thread package.
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This is intended to be usable independently from Python.
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The implementation for system foobar is in a file thread_foobar.h
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which is included by this file dependent on config settings.
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Stuff shared by all thread_*.h files is collected here. */
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#include "Python.h"
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#ifndef _POSIX_THREADS
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/* This means pthreads are not implemented in libc headers, hence the macro
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not present in unistd.h. But they still can be implemented as an external
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library (e.g. gnu pth in pthread emulation) */
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# ifdef HAVE_PTHREAD_H
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# include <pthread.h> /* _POSIX_THREADS */
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# endif
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#endif
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#ifndef DONT_HAVE_STDIO_H
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#include <stdio.h>
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#endif
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#include <stdlib.h>
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#ifdef __sgi
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#ifndef HAVE_PTHREAD_H /* XXX Need to check in configure.in */
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#undef _POSIX_THREADS
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#endif
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#endif
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#include "pythread.h"
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#ifndef _POSIX_THREADS
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#ifdef __sgi
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#define SGI_THREADS
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#endif
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#ifdef HAVE_THREAD_H
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#define SOLARIS_THREADS
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#endif
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#if defined(sun) && !defined(SOLARIS_THREADS)
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#define SUN_LWP
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#endif
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/* Check if we're running on HP-UX and _SC_THREADS is defined. If so, then
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enough of the Posix threads package is implimented to support python
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threads.
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This is valid for HP-UX 11.23 running on an ia64 system. If needed, add
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a check of __ia64 to verify that we're running on a ia64 system instead
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of a pa-risc system.
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*/
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#ifdef __hpux
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#ifdef _SC_THREADS
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#define _POSIX_THREADS
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#endif
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#endif
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#endif /* _POSIX_THREADS */
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#ifdef Py_DEBUG
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static int thread_debug = 0;
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#define dprintf(args) (void)((thread_debug & 1) && printf args)
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#define d2printf(args) ((thread_debug & 8) && printf args)
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#else
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#define dprintf(args)
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#define d2printf(args)
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#endif
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static int initialized;
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static void PyThread__init_thread(void); /* Forward */
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void PyThread_init_thread(void)
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{
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#ifdef Py_DEBUG
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char *p = getenv("THREADDEBUG");
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if (p) {
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if (*p)
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thread_debug = atoi(p);
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else
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thread_debug = 1;
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}
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#endif /* Py_DEBUG */
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if (initialized)
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return;
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initialized = 1;
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dprintf(("PyThread_init_thread called\n"));
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PyThread__init_thread();
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}
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#ifdef SGI_THREADS
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#include "thread_sgi.h"
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#endif
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#ifdef SOLARIS_THREADS
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#include "thread_solaris.h"
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#endif
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#ifdef SUN_LWP
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#include "thread_lwp.h"
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#endif
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#ifdef HAVE_PTH
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#include "thread_pth.h"
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#undef _POSIX_THREADS
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#endif
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#ifdef _POSIX_THREADS
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#include "thread_pthread.h"
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#endif
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#ifdef C_THREADS
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#include "thread_cthread.h"
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#endif
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#ifdef NT_THREADS
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#include "thread_nt.h"
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#endif
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#ifdef OS2_THREADS
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#include "thread_os2.h"
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#endif
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#ifdef BEOS_THREADS
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#include "thread_beos.h"
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#endif
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#ifdef WINCE_THREADS
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#include "thread_wince.h"
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#endif
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#ifdef PLAN9_THREADS
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#include "thread_plan9.h"
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#endif
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#ifdef ATHEOS_THREADS
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#include "thread_atheos.h"
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#endif
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/*
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#ifdef FOOBAR_THREADS
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#include "thread_foobar.h"
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#endif
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*/
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#ifndef Py_HAVE_NATIVE_TLS
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/* If the platform has not supplied a platform specific
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TLS implementation, provide our own.
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This code stolen from "thread_sgi.h", where it was the only
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implementation of an existing Python TLS API.
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*/
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/* ------------------------------------------------------------------------
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Per-thread data ("key") support.
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Use PyThread_create_key() to create a new key. This is typically shared
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across threads.
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Use PyThread_set_key_value(thekey, value) to associate void* value with
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thekey in the current thread. Each thread has a distinct mapping of thekey
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to a void* value. Caution: if the current thread already has a mapping
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for thekey, value is ignored.
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Use PyThread_get_key_value(thekey) to retrieve the void* value associated
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with thekey in the current thread. This returns NULL if no value is
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associated with thekey in the current thread.
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Use PyThread_delete_key_value(thekey) to forget the current thread's associated
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value for thekey. PyThread_delete_key(thekey) forgets the values associated
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with thekey across *all* threads.
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While some of these functions have error-return values, none set any
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Python exception.
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None of the functions does memory management on behalf of the void* values.
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You need to allocate and deallocate them yourself. If the void* values
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happen to be PyObject*, these functions don't do refcount operations on
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them either.
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The GIL does not need to be held when calling these functions; they supply
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their own locking. This isn't true of PyThread_create_key(), though (see
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next paragraph).
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There's a hidden assumption that PyThread_create_key() will be called before
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any of the other functions are called. There's also a hidden assumption
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that calls to PyThread_create_key() are serialized externally.
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------------------------------------------------------------------------ */
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/* A singly-linked list of struct key objects remembers all the key->value
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* associations. File static keyhead heads the list. keymutex is used
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* to enforce exclusion internally.
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*/
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struct key {
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/* Next record in the list, or NULL if this is the last record. */
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struct key *next;
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/* The thread id, according to PyThread_get_thread_ident(). */
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long id;
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/* The key and its associated value. */
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int key;
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void *value;
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};
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static struct key *keyhead = NULL;
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static PyThread_type_lock keymutex = NULL;
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static int nkeys = 0; /* PyThread_create_key() hands out nkeys+1 next */
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/* Internal helper.
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* If the current thread has a mapping for key, the appropriate struct key*
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* is returned. NB: value is ignored in this case!
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* If there is no mapping for key in the current thread, then:
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* If value is NULL, NULL is returned.
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* Else a mapping of key to value is created for the current thread,
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* and a pointer to a new struct key* is returned; except that if
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* malloc() can't find room for a new struct key*, NULL is returned.
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* So when value==NULL, this acts like a pure lookup routine, and when
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* value!=NULL, this acts like dict.setdefault(), returning an existing
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* mapping if one exists, else creating a new mapping.
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*
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* Caution: this used to be too clever, trying to hold keymutex only
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* around the "p->next = keyhead; keyhead = p" pair. That allowed
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* another thread to mutate the list, via key deletion, concurrent with
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* find_key() crawling over the list. Hilarity ensued. For example, when
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* the for-loop here does "p = p->next", p could end up pointing at a
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* record that PyThread_delete_key_value() was concurrently free()'ing.
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* That could lead to anything, from failing to find a key that exists, to
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* segfaults. Now we lock the whole routine.
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*/
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static struct key *
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find_key(int key, void *value)
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{
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struct key *p;
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long id = PyThread_get_thread_ident();
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PyThread_acquire_lock(keymutex, 1);
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for (p = keyhead; p != NULL; p = p->next) {
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if (p->id == id && p->key == key)
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goto Done;
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}
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if (value == NULL) {
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assert(p == NULL);
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goto Done;
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}
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p = (struct key *)malloc(sizeof(struct key));
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if (p != NULL) {
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p->id = id;
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p->key = key;
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p->value = value;
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p->next = keyhead;
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keyhead = p;
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}
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Done:
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PyThread_release_lock(keymutex);
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return p;
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}
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/* Return a new key. This must be called before any other functions in
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* this family, and callers must arrange to serialize calls to this
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* function. No violations are detected.
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*/
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int
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PyThread_create_key(void)
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{
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/* All parts of this function are wrong if it's called by multiple
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* threads simultaneously.
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*/
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if (keymutex == NULL)
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keymutex = PyThread_allocate_lock();
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return ++nkeys;
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}
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/* Forget the associations for key across *all* threads. */
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void
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PyThread_delete_key(int key)
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{
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struct key *p, **q;
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PyThread_acquire_lock(keymutex, 1);
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q = &keyhead;
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while ((p = *q) != NULL) {
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if (p->key == key) {
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*q = p->next;
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free((void *)p);
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/* NB This does *not* free p->value! */
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}
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else
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q = &p->next;
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}
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PyThread_release_lock(keymutex);
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}
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/* Confusing: If the current thread has an association for key,
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* value is ignored, and 0 is returned. Else an attempt is made to create
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* an association of key to value for the current thread. 0 is returned
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* if that succeeds, but -1 is returned if there's not enough memory
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* to create the association. value must not be NULL.
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*/
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int
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PyThread_set_key_value(int key, void *value)
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{
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struct key *p;
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assert(value != NULL);
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p = find_key(key, value);
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if (p == NULL)
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return -1;
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else
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return 0;
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}
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/* Retrieve the value associated with key in the current thread, or NULL
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* if the current thread doesn't have an association for key.
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*/
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void *
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PyThread_get_key_value(int key)
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{
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struct key *p = find_key(key, NULL);
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if (p == NULL)
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return NULL;
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else
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return p->value;
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}
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/* Forget the current thread's association for key, if any. */
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void
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PyThread_delete_key_value(int key)
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{
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long id = PyThread_get_thread_ident();
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struct key *p, **q;
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PyThread_acquire_lock(keymutex, 1);
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q = &keyhead;
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while ((p = *q) != NULL) {
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if (p->key == key && p->id == id) {
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*q = p->next;
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free((void *)p);
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/* NB This does *not* free p->value! */
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break;
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}
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else
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q = &p->next;
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}
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PyThread_release_lock(keymutex);
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}
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#endif /* Py_HAVE_NATIVE_TLS */
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