/* Creating and controlling threads.
- Copyright (C) 2005-2008 Free Software Foundation, Inc.
+ Copyright (C) 2005-2011 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
#include <config.h>
+/* Specification. */
#include "glthread/thread.h"
#include <stdlib.h>
#if USE_WIN32_THREADS
+#include <process.h>
+
/* -------------------------- gl_thread_t datatype -------------------------- */
-/* Use a wrapper function, instead of adding WINAPI through a cast.
- This struct also holds the thread's exit value. */
-struct thread_extra
- {
- /* Fields for managing the association between thread id and handle. */
- DWORD volatile id;
- HANDLE volatile handle;
- struct thread_extra * volatile next;
- /* Fields for managing the exit value. */
- void * volatile result;
- /* Fields for managing the thread start. */
- void * (*func) (void *);
- void *arg;
- };
-
-/* Linked list of thread_extra of running or zombie (not-yet-joined)
- threads.
- TODO: Use a hash table indexed by id instead of a linked list. */
-static struct thread_extra *running_threads /* = NULL */;
-
-/* Lock protecting running_threads. */
-gl_lock_define_initialized(static, running_lock)
-
-static DWORD WINAPI
-wrapper_func (void *varg)
+/* The Thread-Local Storage (TLS) key that allows to access each thread's
+ 'struct gl_thread_struct *' pointer. */
+static DWORD self_key = (DWORD)-1;
+
+/* Initializes self_key. This function must only be called once. */
+static void
+do_init_self_key (void)
{
- struct thread_extra *xarg = (struct thread_extra *)varg;
+ self_key = TlsAlloc ();
+ /* If this fails, we're hosed. */
+ if (self_key == (DWORD)-1)
+ abort ();
+}
+
+/* Initializes self_key. */
+static void
+init_self_key (void)
+{
+ gl_once_define(static, once)
+ gl_once (once, do_init_self_key);
+}
- xarg->id = GetCurrentThreadId ();
- /* Add xarg to the list of running thread_extra. */
- gl_lock_lock (running_lock);
- if (!(xarg->id == GetCurrentThreadId ()))
+/* This structure contains information about a thread.
+ It is stored in TLS under key self_key. */
+struct gl_thread_struct
+{
+ /* Fields for managing the handle. */
+ HANDLE volatile handle;
+ CRITICAL_SECTION handle_lock;
+ /* Fields for managing the exit value. */
+ void * volatile result;
+ /* Fields for managing the thread start. */
+ void * (*func) (void *);
+ void *arg;
+};
+
+/* Return a real HANDLE object for the current thread. */
+static inline HANDLE
+get_current_thread_handle (void)
+{
+ HANDLE this_handle;
+
+ /* GetCurrentThread() returns a pseudo-handle, i.e. only a symbolic
+ identifier, not a real handle. */
+ if (!DuplicateHandle (GetCurrentProcess (), GetCurrentThread (),
+ GetCurrentProcess (), &this_handle,
+ 0, FALSE, DUPLICATE_SAME_ACCESS))
abort ();
- xarg->next = running_threads;
- running_threads = xarg;
- gl_lock_unlock (running_lock);
+ return this_handle;
+}
+
+gl_thread_t
+gl_thread_self_func (void)
+{
+ gl_thread_t thread;
+
+ if (self_key == (DWORD)-1)
+ init_self_key ();
+ thread = TlsGetValue (self_key);
+ if (thread == NULL)
+ {
+ /* This happens only in threads that have not been created through
+ glthread_create(), such as the main thread. */
+ for (;;)
+ {
+ thread =
+ (struct gl_thread_struct *)
+ malloc (sizeof (struct gl_thread_struct));
+ if (thread != NULL)
+ break;
+ /* Memory allocation failed. There is not much we can do. Have to
+ busy-loop, waiting for the availability of memory. */
+ Sleep (1);
+ }
+
+ thread->handle = get_current_thread_handle ();
+ InitializeCriticalSection (&thread->handle_lock);
+ thread->result = NULL; /* just to be deterministic */
+ TlsSetValue (self_key, thread);
+ }
+ return thread;
+}
+
+/* The main function of a freshly creating thread. It's a wrapper around
+ the FUNC and ARG arguments passed to glthread_create_func. */
+static unsigned int WINAPI
+wrapper_func (void *varg)
+{
+ struct gl_thread_struct *thread = (struct gl_thread_struct *)varg;
+
+ EnterCriticalSection (&thread->handle_lock);
+ /* Create a new handle for the thread only if the parent thread did not yet
+ fill in the handle. */
+ if (thread->handle == NULL)
+ thread->handle = get_current_thread_handle ();
+ LeaveCriticalSection (&thread->handle_lock);
+
+ if (self_key == (DWORD)-1)
+ init_self_key ();
+ TlsSetValue (self_key, thread);
/* Run the thread. Store the exit value if the thread was not terminated
otherwise. */
- xarg->result = xarg->func (xarg->arg);
+ thread->result = thread->func (thread->arg);
return 0;
}
int
glthread_create_func (gl_thread_t *threadp, void * (*func) (void *), void *arg)
{
- struct thread_extra *x =
- (struct thread_extra *) malloc (sizeof (struct thread_extra));
- if (x == NULL)
+ struct gl_thread_struct *thread =
+ (struct gl_thread_struct *) malloc (sizeof (struct gl_thread_struct));
+ if (thread == NULL)
return ENOMEM;
- x->result = NULL; /* just to be deterministic */
- x->func = func;
- x->arg = arg;
+ thread->handle = NULL;
+ InitializeCriticalSection (&thread->handle_lock);
+ thread->result = NULL; /* just to be deterministic */
+ thread->func = func;
+ thread->arg = arg;
+
{
- DWORD thread_id;
+ unsigned int thread_id;
HANDLE thread_handle;
- gl_lock_lock (running_lock);
- thread_handle = CreateThread (NULL, 100000, wrapper_func, x, 0, &thread_id);
+ thread_handle = (HANDLE)
+ _beginthreadex (NULL, 100000, wrapper_func, thread, 0, &thread_id);
+ /* calls CreateThread with the same arguments */
if (thread_handle == NULL)
{
- gl_lock_unlock (running_lock);
- return EAGAIN;
+ DeleteCriticalSection (&thread->handle_lock);
+ free (thread);
+ return EAGAIN;
}
- x->id = thread_id;
- x->handle = thread_handle;
- gl_lock_unlock (running_lock);
- *threadp = thread_id;
+
+ EnterCriticalSection (&thread->handle_lock);
+ if (thread->handle == NULL)
+ thread->handle = thread_handle;
+ else
+ /* thread->handle was already set by the thread itself. */
+ CloseHandle (thread_handle);
+ LeaveCriticalSection (&thread->handle_lock);
+
+ *threadp = thread;
return 0;
}
}
int
glthread_join_func (gl_thread_t thread, void **retvalp)
{
- HANDLE thread_handle;
+ if (thread == NULL)
+ return EINVAL;
if (thread == gl_thread_self ())
return EDEADLK;
- /* Find the thread handle that corresponds to the thread id.
- The thread argument must come from either the parent thread or from the
- thread itself. So at this point, either glthread_create_func was
- completed (and x->handle set), or x->func was invoked (and that can
- only be after the running_lock was acquired, hence after
- glthread_create_func released it, hence x->handle is set as well). */
- thread_handle = NULL;
- gl_lock_lock (running_lock);
- {
- struct thread_extra *x;
- for (x = running_threads; x != NULL; x = x->next)
- if (x->id == thread)
- {
- thread_handle = x->handle;
- break;
- }
- }
- gl_lock_unlock (running_lock);
- if (thread_handle == NULL)
- return ESRCH;
-
- if (WaitForSingleObject (thread_handle, INFINITE) == WAIT_FAILED)
+ if (WaitForSingleObject (thread->handle, INFINITE) == WAIT_FAILED)
return EINVAL;
- /* Remove the 'struct thread_extra' from running_threads. */
- gl_lock_lock (running_lock);
- {
- struct thread_extra **xp;
- for (xp = &running_threads; *xp != NULL; xp = &(*xp)->next)
- if ((*xp)->id == thread)
- {
- struct thread_extra *x = *xp;
- if (retvalp != NULL)
- *retvalp = x->result;
- if (x->handle != thread_handle)
- abort ();
- *xp = x->next;
- free (x);
- break;
- }
- }
- gl_lock_unlock (running_lock);
+ if (retvalp != NULL)
+ *retvalp = thread->result;
- CloseHandle (thread_handle);
+ DeleteCriticalSection (&thread->handle_lock);
+ CloseHandle (thread->handle);
+ free (thread);
return 0;
}
int
gl_thread_exit_func (void *retval)
{
- DWORD this_thread = GetCurrentThreadId ();
-
- /* Store the exit value in the appropriate element of running_threads. */
- gl_lock_lock (running_lock);
- {
- struct thread_extra *x;
- for (x = running_threads; x != NULL; x = x->next)
- if (x->id == this_thread)
- {
- x->result = retval;
- break;
- }
- }
- gl_lock_unlock (running_lock);
-
- ExitThread (0);
+ gl_thread_t thread = gl_thread_self ();
+ thread->result = retval;
+ _endthreadex (0); /* calls ExitThread (0) */
+ abort ();
}
#endif
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