#include <config.h>
+/* Specification. */
#include "glthread/thread.h"
#include <stdlib.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;
- CRITICAL_SECTION handle_lock;
- 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)
+/* 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)
+{
+ 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);
+}
+
+/* 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 ();
+ 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 DWORD WINAPI
wrapper_func (void *varg)
{
- struct thread_extra *xarg = (struct thread_extra *)varg;
+ struct gl_thread_struct *thread = (struct gl_thread_struct *)varg;
- EnterCriticalSection (&xarg->handle_lock);
- xarg->id = GetCurrentThreadId ();
+ EnterCriticalSection (&thread->handle_lock);
/* Create a new handle for the thread only if the parent thread did not yet
fill in the handle. */
- if (xarg->handle == NULL)
- {
- HANDLE this_thread;
- if (!DuplicateHandle (GetCurrentProcess (), GetCurrentThread (),
- GetCurrentProcess (), &this_thread,
- 0, FALSE, DUPLICATE_SAME_ACCESS))
- abort ();
- xarg->handle = this_thread;
- }
- LeaveCriticalSection (&xarg->handle_lock);
- /* Add xarg to the list of running thread_extra. */
- gl_lock_lock (running_lock);
- if (!(xarg->id == GetCurrentThreadId ()))
- abort ();
- xarg->next = running_threads;
- running_threads = xarg;
- gl_lock_unlock (running_lock);
+ 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->handle = NULL;
- InitializeCriticalSection (&x->handle_lock);
- 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;
HANDLE thread_handle;
- thread_handle = CreateThread (NULL, 100000, wrapper_func, x, 0, &thread_id);
+ thread_handle =
+ CreateThread (NULL, 100000, wrapper_func, thread, 0, &thread_id);
if (thread_handle == NULL)
{
- DeleteCriticalSection (&x->handle_lock);
- free (x);
+ DeleteCriticalSection (&thread->handle_lock);
+ free (thread);
return EAGAIN;
}
- EnterCriticalSection (&x->handle_lock);
- x->id = thread_id;
- if (x->handle == NULL)
- x->handle = thread_handle;
+
+ EnterCriticalSection (&thread->handle_lock);
+ if (thread->handle == NULL)
+ thread->handle = thread_handle;
else
- /* x->handle was already set by the thread itself. */
+ /* thread->handle was already set by the thread itself. */
CloseHandle (thread_handle);
- LeaveCriticalSection (&x->handle_lock);
- *threadp = thread_id;
+ 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 or
- wrapper_func (whichever was executed first) has filled in x->handle. */
- 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 * volatile *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;
- DeleteCriticalSection (&x->handle_lock);
- 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);
-
+ gl_thread_t thread = gl_thread_self ();
+ thread->result = retval;
ExitThread (0);
}
/* -------------------------- gl_thread_t datatype -------------------------- */
-/* The gl_thread_t is the thread id, not the thread handle. If it were the
- thread handle, it would be hard to implement gl_thread_self()
- (since GetCurrentThread () returns a pseudo-handle,
- DuplicateHandle (GetCurrentThread ()) returns a handle that must be closed
- afterwards, and there is no function for quickly retrieving a thread handle
- from its id). */
-typedef DWORD gl_thread_t;
+/* The gl_thread_t is a pointer to a structure in memory.
+ Why not the thread handle? If it were the thread handle, it would be hard
+ to implement gl_thread_self() (since GetCurrentThread () returns a pseudo-
+ handle, DuplicateHandle (GetCurrentThread ()) returns a handle that must be
+ closed afterwards, and there is no function for quickly retrieving a thread
+ handle from its id).
+ Why not the thread id? I tried it. It did not work: Sometimes ids appeared
+ that did not belong to running threads, and glthread_join failed with ESRCH.
+ */
+typedef struct gl_thread_struct *gl_thread_t;
# define glthread_create(THREADP, FUNC, ARG) \
glthread_create_func (THREADP, FUNC, ARG)
# define glthread_sigmask(HOW, SET, OSET) \
# define glthread_join(THREAD, RETVALP) \
glthread_join_func (THREAD, RETVALP)
# define gl_thread_self() \
- GetCurrentThreadId ()
+ gl_thread_self_func ()
# define gl_thread_exit(RETVAL) \
gl_thread_exit_func (RETVAL)
# define glthread_atfork(PREPARE_FUNC, PARENT_FUNC, CHILD_FUNC) 0
extern int glthread_create_func (gl_thread_t *threadp, void * (*func) (void *), void *arg);
extern int glthread_join_func (gl_thread_t thread, void **retvalp);
+extern gl_thread_t gl_thread_self_func (void);
extern int gl_thread_exit_func (void *retval);
# ifdef __cplusplus
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