diff options
Diffstat (limited to 'lib/windows-cond.c')
| -rw-r--r-- | lib/windows-cond.c | 428 |
1 files changed, 428 insertions, 0 deletions
diff --git a/lib/windows-cond.c b/lib/windows-cond.c new file mode 100644 index 0000000..10b7106 --- /dev/null +++ b/lib/windows-cond.c @@ -0,0 +1,428 @@ +/* Condition variables (native Windows implementation). + Copyright (C) 2008-2023 Free Software Foundation, Inc. + + This file is free software: you can redistribute it and/or modify + it under the terms of the GNU Lesser General Public License as + published by the Free Software Foundation; either version 2.1 of the + License, or (at your option) any later version. + + This file is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with this program. If not, see <https://www.gnu.org/licenses/>. */ + +/* Written by Yoann Vandoorselaere <yoann@prelude-ids.org>, 2008, + and Bruno Haible <bruno@clisp.org>, 2008. */ + +#include <config.h> + +/* Specification. */ +#include "windows-cond.h" + +#include <errno.h> +#include <stdlib.h> +#include <sys/time.h> + +/* Don't assume that UNICODE is not defined. */ +#undef CreateEvent +#define CreateEvent CreateEventA + +/* In this file, the waitqueues are implemented as linked lists. */ +#define glwthread_waitqueue_t glwthread_linked_waitqueue_t + +/* All links of a circular list, except the anchor, are of this type, carrying + a payload. */ +struct glwthread_waitqueue_element +{ + struct glwthread_waitqueue_link link; /* must be the first field! */ + HANDLE event; /* Waiting thread, represented by an event. + This field is immutable once initialized. */ +}; + +static void +glwthread_waitqueue_init (glwthread_waitqueue_t *wq) +{ + wq->wq_list.wql_next = &wq->wq_list; + wq->wq_list.wql_prev = &wq->wq_list; +} + +/* Enqueues the current thread, represented by an event, in a wait queue. + Returns NULL if an allocation failure occurs. */ +static struct glwthread_waitqueue_element * +glwthread_waitqueue_add (glwthread_waitqueue_t *wq) +{ + struct glwthread_waitqueue_element *elt; + HANDLE event; + + /* Allocate the memory for the waitqueue element on the heap, not on the + thread's stack. If the thread exits unexpectedly, we prefer to leak + some memory rather than to access unavailable memory and crash. */ + elt = + (struct glwthread_waitqueue_element *) + malloc (sizeof (struct glwthread_waitqueue_element)); + if (elt == NULL) + /* No more memory. */ + return NULL; + + /* Whether the created event is a manual-reset one or an auto-reset one, + does not matter, since we will wait on it only once. */ + event = CreateEvent (NULL, TRUE, FALSE, NULL); + if (event == INVALID_HANDLE_VALUE) + { + /* No way to allocate an event. */ + free (elt); + return NULL; + } + elt->event = event; + /* Insert elt at the end of the circular list. */ + (elt->link.wql_prev = wq->wq_list.wql_prev)->wql_next = &elt->link; + (elt->link.wql_next = &wq->wq_list)->wql_prev = &elt->link; + return elt; +} + +/* Removes the current thread, represented by a + 'struct glwthread_waitqueue_element *', from a wait queue. + Returns true if is was found and removed, false if it was not present. */ +static bool +glwthread_waitqueue_remove (glwthread_waitqueue_t *wq, + struct glwthread_waitqueue_element *elt) +{ + if (elt->link.wql_next != NULL && elt->link.wql_prev != NULL) + { + /* Remove elt from the circular list. */ + struct glwthread_waitqueue_link *prev = elt->link.wql_prev; + struct glwthread_waitqueue_link *next = elt->link.wql_next; + prev->wql_next = next; + next->wql_prev = prev; + elt->link.wql_next = NULL; + elt->link.wql_prev = NULL; + return true; + } + else + return false; +} + +/* Notifies the first thread from a wait queue and dequeues it. */ +static void +glwthread_waitqueue_notify_first (glwthread_waitqueue_t *wq) +{ + if (wq->wq_list.wql_next != &wq->wq_list) + { + struct glwthread_waitqueue_element *elt = + (struct glwthread_waitqueue_element *) wq->wq_list.wql_next; + struct glwthread_waitqueue_link *prev; + struct glwthread_waitqueue_link *next; + + /* Remove elt from the circular list. */ + prev = &wq->wq_list; /* = elt->link.wql_prev; */ + next = elt->link.wql_next; + prev->wql_next = next; + next->wql_prev = prev; + elt->link.wql_next = NULL; + elt->link.wql_prev = NULL; + + SetEvent (elt->event); + /* After the SetEvent, this thread cannot access *elt any more, because + the woken-up thread will quickly call free (elt). */ + } +} + +/* Notifies all threads from a wait queue and dequeues them all. */ +static void +glwthread_waitqueue_notify_all (glwthread_waitqueue_t *wq) +{ + struct glwthread_waitqueue_link *l; + + for (l = wq->wq_list.wql_next; l != &wq->wq_list; ) + { + struct glwthread_waitqueue_element *elt = + (struct glwthread_waitqueue_element *) l; + struct glwthread_waitqueue_link *prev; + struct glwthread_waitqueue_link *next; + + /* Remove elt from the circular list. */ + prev = &wq->wq_list; /* = elt->link.wql_prev; */ + next = elt->link.wql_next; + prev->wql_next = next; + next->wql_prev = prev; + elt->link.wql_next = NULL; + elt->link.wql_prev = NULL; + + SetEvent (elt->event); + /* After the SetEvent, this thread cannot access *elt any more, because + the woken-up thread will quickly call free (elt). */ + + l = next; + } + if (!(wq->wq_list.wql_next == &wq->wq_list + && wq->wq_list.wql_prev == &wq->wq_list)) + abort (); +} + +int +glwthread_cond_init (glwthread_cond_t *cond) +{ + InitializeCriticalSection (&cond->lock); + glwthread_waitqueue_init (&cond->waiters); + + cond->guard.done = 1; + return 0; +} + +int +glwthread_cond_wait (glwthread_cond_t *cond, + void *mutex, int (*mutex_lock) (void *), int (*mutex_unlock) (void *)) +{ + if (!cond->guard.done) + { + if (InterlockedIncrement (&cond->guard.started) == 0) + /* This thread is the first one to need this condition variable. + Initialize it. */ + glwthread_cond_init (cond); + else + { + /* Don't let cond->guard.started grow and wrap around. */ + InterlockedDecrement (&cond->guard.started); + /* Yield the CPU while waiting for another thread to finish + initializing this condition variable. */ + while (!cond->guard.done) + Sleep (0); + } + } + + EnterCriticalSection (&cond->lock); + { + struct glwthread_waitqueue_element *elt = + glwthread_waitqueue_add (&cond->waiters); + LeaveCriticalSection (&cond->lock); + if (elt == NULL) + { + /* Allocation failure. Weird. */ + return EAGAIN; + } + else + { + HANDLE event = elt->event; + int err; + DWORD result; + + /* Now release the mutex and let any other thread take it. */ + err = mutex_unlock (mutex); + if (err != 0) + { + EnterCriticalSection (&cond->lock); + glwthread_waitqueue_remove (&cond->waiters, elt); + LeaveCriticalSection (&cond->lock); + CloseHandle (event); + free (elt); + return err; + } + /* POSIX says: + "If another thread is able to acquire the mutex after the + about-to-block thread has released it, then a subsequent call to + pthread_cond_broadcast() or pthread_cond_signal() in that thread + shall behave as if it were issued after the about-to-block thread + has blocked." + This is fulfilled here, because the thread signalling is done + through SetEvent, not PulseEvent. */ + /* Wait until another thread signals this event. */ + result = WaitForSingleObject (event, INFINITE); + if (result == WAIT_FAILED || result == WAIT_TIMEOUT) + abort (); + CloseHandle (event); + free (elt); + /* The thread which signalled the event already did the bookkeeping: + removed us from the waiters. */ + return mutex_lock (mutex); + } + } +} + +int +glwthread_cond_timedwait (glwthread_cond_t *cond, + void *mutex, int (*mutex_lock) (void *), int (*mutex_unlock) (void *), + const struct timespec *abstime) +{ + if (!cond->guard.done) + { + if (InterlockedIncrement (&cond->guard.started) == 0) + /* This thread is the first one to need this condition variable. + Initialize it. */ + glwthread_cond_init (cond); + else + { + /* Don't let cond->guard.started grow and wrap around. */ + InterlockedDecrement (&cond->guard.started); + /* Yield the CPU while waiting for another thread to finish + initializing this condition variable. */ + while (!cond->guard.done) + Sleep (0); + } + } + + { + struct timeval currtime; + + gettimeofday (&currtime, NULL); + if (currtime.tv_sec > abstime->tv_sec + || (currtime.tv_sec == abstime->tv_sec + && currtime.tv_usec * 1000 >= abstime->tv_nsec)) + return ETIMEDOUT; + + EnterCriticalSection (&cond->lock); + { + struct glwthread_waitqueue_element *elt = + glwthread_waitqueue_add (&cond->waiters); + LeaveCriticalSection (&cond->lock); + if (elt == NULL) + { + /* Allocation failure. Weird. */ + return EAGAIN; + } + else + { + HANDLE event = elt->event; + int err; + DWORD timeout; + DWORD result; + + /* Now release the mutex and let any other thread take it. */ + err = mutex_unlock (mutex); + if (err != 0) + { + EnterCriticalSection (&cond->lock); + glwthread_waitqueue_remove (&cond->waiters, elt); + LeaveCriticalSection (&cond->lock); + CloseHandle (event); + free (elt); + return err; + } + /* POSIX says: + "If another thread is able to acquire the mutex after the + about-to-block thread has released it, then a subsequent call to + pthread_cond_broadcast() or pthread_cond_signal() in that thread + shall behave as if it were issued after the about-to-block thread + has blocked." + This is fulfilled here, because the thread signalling is done + through SetEvent, not PulseEvent. */ + /* Wait until another thread signals this event or until the abstime + passes. */ + gettimeofday (&currtime, NULL); + if (currtime.tv_sec > abstime->tv_sec) + timeout = 0; + else + { + unsigned long seconds = abstime->tv_sec - currtime.tv_sec; + timeout = seconds * 1000; + if (timeout / 1000 != seconds) /* overflow? */ + timeout = INFINITE; + else + { + long milliseconds = + abstime->tv_nsec / 1000000 - currtime.tv_usec / 1000; + if (milliseconds >= 0) + { + timeout += milliseconds; + if (timeout < milliseconds) /* overflow? */ + timeout = INFINITE; + } + else + { + if (timeout >= - milliseconds) + timeout -= (- milliseconds); + else + timeout = 0; + } + } + } + result = WaitForSingleObject (event, timeout); + if (result == WAIT_FAILED) + abort (); + if (result == WAIT_TIMEOUT) + { + EnterCriticalSection (&cond->lock); + if (glwthread_waitqueue_remove (&cond->waiters, elt)) + { + /* The event was not signaled between the WaitForSingleObject + call and the EnterCriticalSection call. */ + if (!(WaitForSingleObject (event, 0) == WAIT_TIMEOUT)) + abort (); + } + else + { + /* The event was signaled between the WaitForSingleObject + call and the EnterCriticalSection call. */ + if (!(WaitForSingleObject (event, 0) == WAIT_OBJECT_0)) + abort (); + /* Produce the right return value. */ + result = WAIT_OBJECT_0; + } + LeaveCriticalSection (&cond->lock); + } + else + { + /* The thread which signalled the event already did the + bookkeeping: removed us from the waiters. */ + } + CloseHandle (event); + free (elt); + /* Take the mutex again. It does not matter whether this is done + before or after the bookkeeping for WAIT_TIMEOUT. */ + err = mutex_lock (mutex); + return (err ? err : + result == WAIT_OBJECT_0 ? 0 : + result == WAIT_TIMEOUT ? ETIMEDOUT : + /* WAIT_FAILED shouldn't happen */ EAGAIN); + } + } + } +} + +int +glwthread_cond_signal (glwthread_cond_t *cond) +{ + if (!cond->guard.done) + return EINVAL; + + EnterCriticalSection (&cond->lock); + /* POSIX says: + "The pthread_cond_broadcast() and pthread_cond_signal() functions shall + have no effect if there are no threads currently blocked on cond." */ + if (cond->waiters.wq_list.wql_next != &cond->waiters.wq_list) + glwthread_waitqueue_notify_first (&cond->waiters); + LeaveCriticalSection (&cond->lock); + + return 0; +} + +int +glwthread_cond_broadcast (glwthread_cond_t *cond) +{ + if (!cond->guard.done) + return EINVAL; + + EnterCriticalSection (&cond->lock); + /* POSIX says: + "The pthread_cond_broadcast() and pthread_cond_signal() functions shall + have no effect if there are no threads currently blocked on cond." + glwthread_waitqueue_notify_all is a nop in this case. */ + glwthread_waitqueue_notify_all (&cond->waiters); + LeaveCriticalSection (&cond->lock); + + return 0; +} + +int +glwthread_cond_destroy (glwthread_cond_t *cond) +{ + if (!cond->guard.done) + return EINVAL; + if (cond->waiters.wq_list.wql_next != &cond->waiters.wq_list) + return EBUSY; + DeleteCriticalSection (&cond->lock); + cond->guard.done = 0; + return 0; +} |