From 72f60af8edb6e1cdee4e5bb34dbc068113b9479c Mon Sep 17 00:00:00 2001 From: Bruno Haible Date: Mon, 15 Jul 2019 02:36:02 +0200 Subject: [PATCH] windows-rwlock: New module. * lib/windows-rwlock.h: New file, extracted from lib/glthread/lock.h. * lib/windows-rwlock.c: New file, extracted from lib/glthread/lock.c. * lib/glthread/lock.h: Include windows-rwlock.h. Don't include windows-initguard.h. (gl_rwlock_t): Define using glwthread_rwlock_t. (gl_rwlock_initializer): Define using GLWTHREAD_RWLOCK_INIT. (glthread_rwlock_init): Define using glwthread_rwlock_init. (glthread_rwlock_rdlock): Define using glwthread_rwlock_rdlock. (glthread_rwlock_wrlock): Define using glwthread_rwlock_wrlock. (glthread_rwlock_unlock): Define using glwthread_rwlock_unlock. (glthread_rwlock_destroy): Define using glwthread_rwlock_destroy. (glthread_rwlock_init_func, glthread_rwlock_rdlock_func, glthread_rwlock_wrlock_func, glthread_rwlock_unlock_func, glthread_rwlock_destroy_func): Remove declarations. * lib/glthread/lock.c (gl_waitqueue_t): Remove type. (gl_waitqueue_init, gl_waitqueue_add, gl_waitqueue_notify_first, gl_waitqueue_notify_all, glthread_rwlock_init_func, glthread_rwlock_rdlock_func, glthread_rwlock_wrlock_func, glthread_rwlock_unlock_func, glthread_rwlock_destroy_func): Remove functions. * modules/windows-rwlock: New file. * modules/lock (Depends-on): Add windows-rwlock. --- ChangeLog | 26 +++ lib/glthread/lock.c | 282 +------------------------------ lib/glthread/lock.h | 41 +---- lib/windows-rwlock.c | 373 +++++++++++++++++++++++++++++++++++++++++ lib/windows-rwlock.h | 68 ++++++++ modules/lock | 1 + modules/windows-rwlock | 28 ++++ 7 files changed, 505 insertions(+), 314 deletions(-) create mode 100644 lib/windows-rwlock.c create mode 100644 lib/windows-rwlock.h create mode 100644 modules/windows-rwlock diff --git a/ChangeLog b/ChangeLog index 316ae110e5..3a0d6f1189 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,29 @@ +2019-07-14 Bruno Haible + + windows-rwlock: New module. + * lib/windows-rwlock.h: New file, extracted from lib/glthread/lock.h. + * lib/windows-rwlock.c: New file, extracted from lib/glthread/lock.c. + * lib/glthread/lock.h: Include windows-rwlock.h. Don't include + windows-initguard.h. + (gl_rwlock_t): Define using glwthread_rwlock_t. + (gl_rwlock_initializer): Define using GLWTHREAD_RWLOCK_INIT. + (glthread_rwlock_init): Define using glwthread_rwlock_init. + (glthread_rwlock_rdlock): Define using glwthread_rwlock_rdlock. + (glthread_rwlock_wrlock): Define using glwthread_rwlock_wrlock. + (glthread_rwlock_unlock): Define using glwthread_rwlock_unlock. + (glthread_rwlock_destroy): Define using glwthread_rwlock_destroy. + (glthread_rwlock_init_func, glthread_rwlock_rdlock_func, + glthread_rwlock_wrlock_func, glthread_rwlock_unlock_func, + glthread_rwlock_destroy_func): Remove declarations. + * lib/glthread/lock.c (gl_waitqueue_t): Remove type. + (gl_waitqueue_init, gl_waitqueue_add, gl_waitqueue_notify_first, + gl_waitqueue_notify_all, glthread_rwlock_init_func, + glthread_rwlock_rdlock_func, glthread_rwlock_wrlock_func, + glthread_rwlock_unlock_func, glthread_rwlock_destroy_func): Remove + functions. + * modules/windows-rwlock: New file. + * modules/lock (Depends-on): Add windows-rwlock. + 2019-07-14 Bruno Haible windows-thread: Add support for creating a thread in detached state. diff --git a/lib/glthread/lock.c b/lib/glthread/lock.c index 89f1f50ab1..852d84d3bb 100644 --- a/lib/glthread/lock.c +++ b/lib/glthread/lock.c @@ -15,7 +15,7 @@ along with this program; if not, see . */ /* Written by Bruno Haible , 2005. - Based on GCC's gthr-posix.h, gthr-posix95.h, gthr-win32.h. */ + Based on GCC's gthr-posix.h, gthr-posix95.h. */ #include @@ -501,286 +501,6 @@ glthread_once_singlethreaded (pthread_once_t *once_control) #if USE_WINDOWS_THREADS -/* ------------------------- gl_rwlock_t datatype ------------------------- */ - -/* In this file, the waitqueues are implemented as circular arrays. */ -#define gl_waitqueue_t gl_carray_waitqueue_t - -static void -gl_waitqueue_init (gl_waitqueue_t *wq) -{ - wq->array = NULL; - wq->count = 0; - wq->alloc = 0; - wq->offset = 0; -} - -/* Enqueues the current thread, represented by an event, in a wait queue. - Returns INVALID_HANDLE_VALUE if an allocation failure occurs. */ -static HANDLE -gl_waitqueue_add (gl_waitqueue_t *wq) -{ - HANDLE event; - unsigned int index; - - if (wq->count == wq->alloc) - { - unsigned int new_alloc = 2 * wq->alloc + 1; - HANDLE *new_array = - (HANDLE *) realloc (wq->array, new_alloc * sizeof (HANDLE)); - if (new_array == NULL) - /* No more memory. */ - return INVALID_HANDLE_VALUE; - /* Now is a good opportunity to rotate the array so that its contents - starts at offset 0. */ - if (wq->offset > 0) - { - unsigned int old_count = wq->count; - unsigned int old_alloc = wq->alloc; - unsigned int old_offset = wq->offset; - unsigned int i; - if (old_offset + old_count > old_alloc) - { - unsigned int limit = old_offset + old_count - old_alloc; - for (i = 0; i < limit; i++) - new_array[old_alloc + i] = new_array[i]; - } - for (i = 0; i < old_count; i++) - new_array[i] = new_array[old_offset + i]; - wq->offset = 0; - } - wq->array = new_array; - wq->alloc = new_alloc; - } - /* 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. */ - return INVALID_HANDLE_VALUE; - index = wq->offset + wq->count; - if (index >= wq->alloc) - index -= wq->alloc; - wq->array[index] = event; - wq->count++; - return event; -} - -/* Notifies the first thread from a wait queue and dequeues it. */ -static void -gl_waitqueue_notify_first (gl_waitqueue_t *wq) -{ - SetEvent (wq->array[wq->offset + 0]); - wq->offset++; - wq->count--; - if (wq->count == 0 || wq->offset == wq->alloc) - wq->offset = 0; -} - -/* Notifies all threads from a wait queue and dequeues them all. */ -static void -gl_waitqueue_notify_all (gl_waitqueue_t *wq) -{ - unsigned int i; - - for (i = 0; i < wq->count; i++) - { - unsigned int index = wq->offset + i; - if (index >= wq->alloc) - index -= wq->alloc; - SetEvent (wq->array[index]); - } - wq->count = 0; - wq->offset = 0; -} - -void -glthread_rwlock_init_func (gl_rwlock_t *lock) -{ - InitializeCriticalSection (&lock->lock); - gl_waitqueue_init (&lock->waiting_readers); - gl_waitqueue_init (&lock->waiting_writers); - lock->runcount = 0; - lock->guard.done = 1; -} - -int -glthread_rwlock_rdlock_func (gl_rwlock_t *lock) -{ - if (!lock->guard.done) - { - if (InterlockedIncrement (&lock->guard.started) == 0) - /* This thread is the first one to need this lock. Initialize it. */ - glthread_rwlock_init (lock); - else - { - /* Don't let lock->guard.started grow and wrap around. */ - InterlockedDecrement (&lock->guard.started); - /* Yield the CPU while waiting for another thread to finish - initializing this lock. */ - while (!lock->guard.done) - Sleep (0); - } - } - EnterCriticalSection (&lock->lock); - /* Test whether only readers are currently running, and whether the runcount - field will not overflow, and whether no writer is waiting. The latter - condition is because POSIX recommends that "write locks shall take - precedence over read locks", to avoid "writer starvation". */ - if (!(lock->runcount + 1 > 0 && lock->waiting_writers.count == 0)) - { - /* This thread has to wait for a while. Enqueue it among the - waiting_readers. */ - HANDLE event = gl_waitqueue_add (&lock->waiting_readers); - if (event != INVALID_HANDLE_VALUE) - { - DWORD result; - LeaveCriticalSection (&lock->lock); - /* Wait until another thread signals this event. */ - result = WaitForSingleObject (event, INFINITE); - if (result == WAIT_FAILED || result == WAIT_TIMEOUT) - abort (); - CloseHandle (event); - /* The thread which signalled the event already did the bookkeeping: - removed us from the waiting_readers, incremented lock->runcount. */ - if (!(lock->runcount > 0)) - abort (); - return 0; - } - else - { - /* Allocation failure. Weird. */ - do - { - LeaveCriticalSection (&lock->lock); - Sleep (1); - EnterCriticalSection (&lock->lock); - } - while (!(lock->runcount + 1 > 0)); - } - } - lock->runcount++; - LeaveCriticalSection (&lock->lock); - return 0; -} - -int -glthread_rwlock_wrlock_func (gl_rwlock_t *lock) -{ - if (!lock->guard.done) - { - if (InterlockedIncrement (&lock->guard.started) == 0) - /* This thread is the first one to need this lock. Initialize it. */ - glthread_rwlock_init (lock); - else - { - /* Don't let lock->guard.started grow and wrap around. */ - InterlockedDecrement (&lock->guard.started); - /* Yield the CPU while waiting for another thread to finish - initializing this lock. */ - while (!lock->guard.done) - Sleep (0); - } - } - EnterCriticalSection (&lock->lock); - /* Test whether no readers or writers are currently running. */ - if (!(lock->runcount == 0)) - { - /* This thread has to wait for a while. Enqueue it among the - waiting_writers. */ - HANDLE event = gl_waitqueue_add (&lock->waiting_writers); - if (event != INVALID_HANDLE_VALUE) - { - DWORD result; - LeaveCriticalSection (&lock->lock); - /* Wait until another thread signals this event. */ - result = WaitForSingleObject (event, INFINITE); - if (result == WAIT_FAILED || result == WAIT_TIMEOUT) - abort (); - CloseHandle (event); - /* The thread which signalled the event already did the bookkeeping: - removed us from the waiting_writers, set lock->runcount = -1. */ - if (!(lock->runcount == -1)) - abort (); - return 0; - } - else - { - /* Allocation failure. Weird. */ - do - { - LeaveCriticalSection (&lock->lock); - Sleep (1); - EnterCriticalSection (&lock->lock); - } - while (!(lock->runcount == 0)); - } - } - lock->runcount--; /* runcount becomes -1 */ - LeaveCriticalSection (&lock->lock); - return 0; -} - -int -glthread_rwlock_unlock_func (gl_rwlock_t *lock) -{ - if (!lock->guard.done) - return EINVAL; - EnterCriticalSection (&lock->lock); - if (lock->runcount < 0) - { - /* Drop a writer lock. */ - if (!(lock->runcount == -1)) - abort (); - lock->runcount = 0; - } - else - { - /* Drop a reader lock. */ - if (!(lock->runcount > 0)) - { - LeaveCriticalSection (&lock->lock); - return EPERM; - } - lock->runcount--; - } - if (lock->runcount == 0) - { - /* POSIX recommends that "write locks shall take precedence over read - locks", to avoid "writer starvation". */ - if (lock->waiting_writers.count > 0) - { - /* Wake up one of the waiting writers. */ - lock->runcount--; - gl_waitqueue_notify_first (&lock->waiting_writers); - } - else - { - /* Wake up all waiting readers. */ - lock->runcount += lock->waiting_readers.count; - gl_waitqueue_notify_all (&lock->waiting_readers); - } - } - LeaveCriticalSection (&lock->lock); - return 0; -} - -int -glthread_rwlock_destroy_func (gl_rwlock_t *lock) -{ - if (!lock->guard.done) - return EINVAL; - if (lock->runcount != 0) - return EBUSY; - DeleteCriticalSection (&lock->lock); - if (lock->waiting_readers.array != NULL) - free (lock->waiting_readers.array); - if (lock->waiting_writers.array != NULL) - free (lock->waiting_writers.array); - lock->guard.done = 0; - return 0; -} - #endif /* ========================================================================= */ diff --git a/lib/glthread/lock.h b/lib/glthread/lock.h index 23d2d98506..78dd67f29f 100644 --- a/lib/glthread/lock.h +++ b/lib/glthread/lock.h @@ -410,8 +410,8 @@ extern int glthread_once_singlethreaded (pthread_once_t *once_control); # define WIN32_LEAN_AND_MEAN /* avoid including junk */ # include -# include "windows-initguard.h" # include "windows-mutex.h" +# include "windows-rwlock.h" # include "windows-recmutex.h" # include "windows-once.h" @@ -450,48 +450,23 @@ typedef glwthread_mutex_t gl_lock_t; /* ------------------------- gl_rwlock_t datatype ------------------------- */ -/* It is impossible to implement read-write locks using plain locks, without - introducing an extra thread dedicated to managing read-write locks. - Therefore here we need to use the low-level Event type. */ - -typedef struct - { - HANDLE *array; /* array of waiting threads, each represented by an event */ - unsigned int count; /* number of waiting threads */ - unsigned int alloc; /* length of allocated array */ - unsigned int offset; /* index of first waiting thread in array */ - } - gl_carray_waitqueue_t; -typedef struct - { - glwthread_initguard_t guard; /* protects the initialization */ - CRITICAL_SECTION lock; /* protects the remaining fields */ - gl_carray_waitqueue_t waiting_readers; /* waiting readers */ - gl_carray_waitqueue_t waiting_writers; /* waiting writers */ - int runcount; /* number of readers running, or -1 when a writer runs */ - } - gl_rwlock_t; +typedef glwthread_rwlock_t gl_rwlock_t; # define gl_rwlock_define(STORAGECLASS, NAME) \ STORAGECLASS gl_rwlock_t NAME; # define gl_rwlock_define_initialized(STORAGECLASS, NAME) \ STORAGECLASS gl_rwlock_t NAME = gl_rwlock_initializer; # define gl_rwlock_initializer \ - { GLWTHREAD_INITGUARD_INIT } + GLWTHREAD_RWLOCK_INIT # define glthread_rwlock_init(LOCK) \ - (glthread_rwlock_init_func (LOCK), 0) + (glwthread_rwlock_init (LOCK), 0) # define glthread_rwlock_rdlock(LOCK) \ - glthread_rwlock_rdlock_func (LOCK) + glwthread_rwlock_rdlock (LOCK) # define glthread_rwlock_wrlock(LOCK) \ - glthread_rwlock_wrlock_func (LOCK) + glwthread_rwlock_wrlock (LOCK) # define glthread_rwlock_unlock(LOCK) \ - glthread_rwlock_unlock_func (LOCK) + glwthread_rwlock_unlock (LOCK) # define glthread_rwlock_destroy(LOCK) \ - glthread_rwlock_destroy_func (LOCK) -extern void glthread_rwlock_init_func (gl_rwlock_t *lock); -extern int glthread_rwlock_rdlock_func (gl_rwlock_t *lock); -extern int glthread_rwlock_wrlock_func (gl_rwlock_t *lock); -extern int glthread_rwlock_unlock_func (gl_rwlock_t *lock); -extern int glthread_rwlock_destroy_func (gl_rwlock_t *lock); + glwthread_rwlock_destroy (LOCK) /* --------------------- gl_recursive_lock_t datatype --------------------- */ diff --git a/lib/windows-rwlock.c b/lib/windows-rwlock.c new file mode 100644 index 0000000000..d777307b09 --- /dev/null +++ b/lib/windows-rwlock.c @@ -0,0 +1,373 @@ +/* Read-write locks (native Windows implementation). + Copyright (C) 2005-2019 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 + the Free Software Foundation; either version 2, or (at your option) + any later version. + + This program 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 General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; if not, see . */ + +/* Written by Bruno Haible , 2005. + Based on GCC's gthr-win32.h. */ + +#include + +/* Specification. */ +#include "windows-rwlock.h" + +#include +#include + +/* In this file, the waitqueues are implemented as circular arrays. */ +#define glwthread_waitqueue_t glwthread_carray_waitqueue_t + +static void +glwthread_waitqueue_init (glwthread_waitqueue_t *wq) +{ + wq->array = NULL; + wq->count = 0; + wq->alloc = 0; + wq->offset = 0; +} + +/* Enqueues the current thread, represented by an event, in a wait queue. + Returns INVALID_HANDLE_VALUE if an allocation failure occurs. */ +static HANDLE +glwthread_waitqueue_add (glwthread_waitqueue_t *wq) +{ + HANDLE event; + unsigned int index; + + if (wq->count == wq->alloc) + { + unsigned int new_alloc = 2 * wq->alloc + 1; + HANDLE *new_array = + (HANDLE *) realloc (wq->array, new_alloc * sizeof (HANDLE)); + if (new_array == NULL) + /* No more memory. */ + return INVALID_HANDLE_VALUE; + /* Now is a good opportunity to rotate the array so that its contents + starts at offset 0. */ + if (wq->offset > 0) + { + unsigned int old_count = wq->count; + unsigned int old_alloc = wq->alloc; + unsigned int old_offset = wq->offset; + unsigned int i; + if (old_offset + old_count > old_alloc) + { + unsigned int limit = old_offset + old_count - old_alloc; + for (i = 0; i < limit; i++) + new_array[old_alloc + i] = new_array[i]; + } + for (i = 0; i < old_count; i++) + new_array[i] = new_array[old_offset + i]; + wq->offset = 0; + } + wq->array = new_array; + wq->alloc = new_alloc; + } + /* 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. */ + return INVALID_HANDLE_VALUE; + index = wq->offset + wq->count; + if (index >= wq->alloc) + index -= wq->alloc; + wq->array[index] = event; + wq->count++; + return event; +} + +/* Notifies the first thread from a wait queue and dequeues it. */ +static void +glwthread_waitqueue_notify_first (glwthread_waitqueue_t *wq) +{ + SetEvent (wq->array[wq->offset + 0]); + wq->offset++; + wq->count--; + if (wq->count == 0 || wq->offset == wq->alloc) + wq->offset = 0; +} + +/* Notifies all threads from a wait queue and dequeues them all. */ +static void +glwthread_waitqueue_notify_all (glwthread_waitqueue_t *wq) +{ + unsigned int i; + + for (i = 0; i < wq->count; i++) + { + unsigned int index = wq->offset + i; + if (index >= wq->alloc) + index -= wq->alloc; + SetEvent (wq->array[index]); + } + wq->count = 0; + wq->offset = 0; +} + +void +glwthread_rwlock_init (glwthread_rwlock_t *lock) +{ + InitializeCriticalSection (&lock->lock); + glwthread_waitqueue_init (&lock->waiting_readers); + glwthread_waitqueue_init (&lock->waiting_writers); + lock->runcount = 0; + lock->guard.done = 1; +} + +int +glwthread_rwlock_rdlock (glwthread_rwlock_t *lock) +{ + if (!lock->guard.done) + { + if (InterlockedIncrement (&lock->guard.started) == 0) + /* This thread is the first one to need this lock. Initialize it. */ + glwthread_rwlock_init (lock); + else + { + /* Don't let lock->guard.started grow and wrap around. */ + InterlockedDecrement (&lock->guard.started); + /* Yield the CPU while waiting for another thread to finish + initializing this lock. */ + while (!lock->guard.done) + Sleep (0); + } + } + EnterCriticalSection (&lock->lock); + /* Test whether only readers are currently running, and whether the runcount + field will not overflow, and whether no writer is waiting. The latter + condition is because POSIX recommends that "write locks shall take + precedence over read locks", to avoid "writer starvation". */ + if (!(lock->runcount + 1 > 0 && lock->waiting_writers.count == 0)) + { + /* This thread has to wait for a while. Enqueue it among the + waiting_readers. */ + HANDLE event = glwthread_waitqueue_add (&lock->waiting_readers); + if (event != INVALID_HANDLE_VALUE) + { + DWORD result; + LeaveCriticalSection (&lock->lock); + /* Wait until another thread signals this event. */ + result = WaitForSingleObject (event, INFINITE); + if (result == WAIT_FAILED || result == WAIT_TIMEOUT) + abort (); + CloseHandle (event); + /* The thread which signalled the event already did the bookkeeping: + removed us from the waiting_readers, incremented lock->runcount. */ + if (!(lock->runcount > 0)) + abort (); + return 0; + } + else + { + /* Allocation failure. Weird. */ + do + { + LeaveCriticalSection (&lock->lock); + Sleep (1); + EnterCriticalSection (&lock->lock); + } + while (!(lock->runcount + 1 > 0)); + } + } + lock->runcount++; + LeaveCriticalSection (&lock->lock); + return 0; +} + +int +glwthread_rwlock_wrlock (glwthread_rwlock_t *lock) +{ + if (!lock->guard.done) + { + if (InterlockedIncrement (&lock->guard.started) == 0) + /* This thread is the first one to need this lock. Initialize it. */ + glwthread_rwlock_init (lock); + else + { + /* Don't let lock->guard.started grow and wrap around. */ + InterlockedDecrement (&lock->guard.started); + /* Yield the CPU while waiting for another thread to finish + initializing this lock. */ + while (!lock->guard.done) + Sleep (0); + } + } + EnterCriticalSection (&lock->lock); + /* Test whether no readers or writers are currently running. */ + if (!(lock->runcount == 0)) + { + /* This thread has to wait for a while. Enqueue it among the + waiting_writers. */ + HANDLE event = glwthread_waitqueue_add (&lock->waiting_writers); + if (event != INVALID_HANDLE_VALUE) + { + DWORD result; + LeaveCriticalSection (&lock->lock); + /* Wait until another thread signals this event. */ + result = WaitForSingleObject (event, INFINITE); + if (result == WAIT_FAILED || result == WAIT_TIMEOUT) + abort (); + CloseHandle (event); + /* The thread which signalled the event already did the bookkeeping: + removed us from the waiting_writers, set lock->runcount = -1. */ + if (!(lock->runcount == -1)) + abort (); + return 0; + } + else + { + /* Allocation failure. Weird. */ + do + { + LeaveCriticalSection (&lock->lock); + Sleep (1); + EnterCriticalSection (&lock->lock); + } + while (!(lock->runcount == 0)); + } + } + lock->runcount--; /* runcount becomes -1 */ + LeaveCriticalSection (&lock->lock); + return 0; +} + +int +glwthread_rwlock_tryrdlock (glwthread_rwlock_t *lock) +{ + if (!lock->guard.done) + { + if (InterlockedIncrement (&lock->guard.started) == 0) + /* This thread is the first one to need this lock. Initialize it. */ + glwthread_rwlock_init (lock); + else + { + /* Don't let lock->guard.started grow and wrap around. */ + InterlockedDecrement (&lock->guard.started); + /* Yield the CPU while waiting for another thread to finish + initializing this lock. */ + while (!lock->guard.done) + Sleep (0); + } + } + /* It's OK to wait for this critical section, because it is never taken for a + long time. */ + EnterCriticalSection (&lock->lock); + /* Test whether only readers are currently running, and whether the runcount + field will not overflow, and whether no writer is waiting. The latter + condition is because POSIX recommends that "write locks shall take + precedence over read locks", to avoid "writer starvation". */ + if (!(lock->runcount + 1 > 0 && lock->waiting_writers.count == 0)) + { + /* This thread would have to wait for a while. Return instead. */ + LeaveCriticalSection (&lock->lock); + return EBUSY; + } + lock->runcount++; + LeaveCriticalSection (&lock->lock); + return 0; +} + +int +glwthread_rwlock_trywrlock (glwthread_rwlock_t *lock) +{ + if (!lock->guard.done) + { + if (InterlockedIncrement (&lock->guard.started) == 0) + /* This thread is the first one to need this lock. Initialize it. */ + glwthread_rwlock_init (lock); + else + { + /* Don't let lock->guard.started grow and wrap around. */ + InterlockedDecrement (&lock->guard.started); + /* Yield the CPU while waiting for another thread to finish + initializing this lock. */ + while (!lock->guard.done) + Sleep (0); + } + } + /* It's OK to wait for this critical section, because it is never taken for a + long time. */ + EnterCriticalSection (&lock->lock); + /* Test whether no readers or writers are currently running. */ + if (!(lock->runcount == 0)) + { + /* This thread would have to wait for a while. Return instead. */ + LeaveCriticalSection (&lock->lock); + return EBUSY; + } + lock->runcount--; /* runcount becomes -1 */ + LeaveCriticalSection (&lock->lock); + return 0; +} + +int +glwthread_rwlock_unlock (glwthread_rwlock_t *lock) +{ + if (!lock->guard.done) + return EINVAL; + EnterCriticalSection (&lock->lock); + if (lock->runcount < 0) + { + /* Drop a writer lock. */ + if (!(lock->runcount == -1)) + abort (); + lock->runcount = 0; + } + else + { + /* Drop a reader lock. */ + if (!(lock->runcount > 0)) + { + LeaveCriticalSection (&lock->lock); + return EPERM; + } + lock->runcount--; + } + if (lock->runcount == 0) + { + /* POSIX recommends that "write locks shall take precedence over read + locks", to avoid "writer starvation". */ + if (lock->waiting_writers.count > 0) + { + /* Wake up one of the waiting writers. */ + lock->runcount--; + glwthread_waitqueue_notify_first (&lock->waiting_writers); + } + else + { + /* Wake up all waiting readers. */ + lock->runcount += lock->waiting_readers.count; + glwthread_waitqueue_notify_all (&lock->waiting_readers); + } + } + LeaveCriticalSection (&lock->lock); + return 0; +} + +int +glwthread_rwlock_destroy (glwthread_rwlock_t *lock) +{ + if (!lock->guard.done) + return EINVAL; + if (lock->runcount != 0) + return EBUSY; + DeleteCriticalSection (&lock->lock); + if (lock->waiting_readers.array != NULL) + free (lock->waiting_readers.array); + if (lock->waiting_writers.array != NULL) + free (lock->waiting_writers.array); + lock->guard.done = 0; + return 0; +} diff --git a/lib/windows-rwlock.h b/lib/windows-rwlock.h new file mode 100644 index 0000000000..ff4272a589 --- /dev/null +++ b/lib/windows-rwlock.h @@ -0,0 +1,68 @@ +/* Read-write locks (native Windows implementation). + Copyright (C) 2005-2019 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 + the Free Software Foundation; either version 2, or (at your option) + any later version. + + This program 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 General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; if not, see . */ + +/* Written by Bruno Haible , 2005. + Based on GCC's gthr-win32.h. */ + +#ifndef _WINDOWS_RWLOCK_H +#define _WINDOWS_RWLOCK_H + +#define WIN32_LEAN_AND_MEAN /* avoid including junk */ +#include + +#include "windows-initguard.h" + +/* It is impossible to implement read-write locks using plain locks, without + introducing an extra thread dedicated to managing read-write locks. + Therefore here we need to use the low-level Event type. */ + +typedef struct + { + HANDLE *array; /* array of waiting threads, each represented by an event */ + unsigned int count; /* number of waiting threads */ + unsigned int alloc; /* length of allocated array */ + unsigned int offset; /* index of first waiting thread in array */ + } + glwthread_carray_waitqueue_t; +typedef struct + { + glwthread_initguard_t guard; /* protects the initialization */ + CRITICAL_SECTION lock; /* protects the remaining fields */ + glwthread_carray_waitqueue_t waiting_readers; /* waiting readers */ + glwthread_carray_waitqueue_t waiting_writers; /* waiting writers */ + int runcount; /* number of readers running, or -1 when a writer runs */ + } + glwthread_rwlock_t; + +#define GLWTHREAD_RWLOCK_INIT { GLWTHREAD_INITGUARD_INIT } + +#ifdef __cplusplus +extern "C" { +#endif + +extern void glwthread_rwlock_init (glwthread_rwlock_t *lock); +extern int glwthread_rwlock_rdlock (glwthread_rwlock_t *lock); +extern int glwthread_rwlock_wrlock (glwthread_rwlock_t *lock); +extern int glwthread_rwlock_tryrdlock (glwthread_rwlock_t *lock); +extern int glwthread_rwlock_trywrlock (glwthread_rwlock_t *lock); +extern int glwthread_rwlock_unlock (glwthread_rwlock_t *lock); +extern int glwthread_rwlock_destroy (glwthread_rwlock_t *lock); + +#ifdef __cplusplus +} +#endif + +#endif /* _WINDOWS_RWLOCK_H */ diff --git a/modules/lock b/modules/lock index 0be823c76b..4b390ba765 100644 --- a/modules/lock +++ b/modules/lock @@ -11,6 +11,7 @@ Depends-on: extensions threadlib windows-mutex [test $gl_threads_api = windows] +windows-rwlock [test $gl_threads_api = windows] windows-recmutex [test $gl_threads_api = windows] windows-once [test $gl_threads_api = windows] diff --git a/modules/windows-rwlock b/modules/windows-rwlock new file mode 100644 index 0000000000..665d60245e --- /dev/null +++ b/modules/windows-rwlock @@ -0,0 +1,28 @@ +Description: +Read-write locks (native Windows implementation). + +Files: +lib/windows-rwlock.h +lib/windows-rwlock.c +lib/windows-initguard.h + +Depends-on: + +configure.ac: +AC_REQUIRE([AC_CANONICAL_HOST]) +case "$host_os" in + mingw*) + AC_LIBOBJ([windows-rwlock]) + ;; +esac + +Makefile.am: + +Include: +"windows-rwlock.h" + +License: +LGPLv2+ + +Maintainer: +all -- 2.39.5