Replace SetEvent synchronization with condition variables

It's cleaner, more stable and works pretty much the same way as the
pthread version. The downside is that the minimum target for the
library is now Windows Vista, or Server 2008. But both are over a
decade old anyway, so this shouldn't be an issue.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

3 files changed, 16 insertions, 31 deletions

diff --git a/lib/sqfs/Makemodule.am b/lib/sqfs/Makemodule.am
index ad3b4de..228d3e9 100644
--- a/lib/sqfs/Makemodule.am
+++ b/lib/sqfs/Makemodule.am
@@ -35,6 +35,7 @@ libsquashfs_la_LIBADD += $(ZSTD_LIBS) $(PTHREAD_LIBS)
 
 if WINDOWS
 libsquashfs_la_SOURCES += lib/sqfs/win32/io_file.c
+libsquashfs_la_CFLAGS += -DWINVER=0x0600 -D_WIN32_WINNT=0x0600
 libsquashfs_la_CFLAGS += -Wc,-static-libgcc
 libsquashfs_la_LDFLAGS += -no-undefined -avoid-version
 else
diff --git a/lib/sqfs/data_writer/internal.h b/lib/sqfs/data_writer/internal.h
index 312922b..ea8fe79 100644
--- a/lib/sqfs/data_writer/internal.h
+++ b/lib/sqfs/data_writer/internal.h
@@ -58,8 +58,8 @@ struct sqfs_data_writer_t {
 	pthread_cond_t done_cond;
 #elif defined(_WIN32) || defined(__WINDOWS__)
 	CRITICAL_SECTION mtx;
-	HANDLE queue_cond;
-	HANDLE done_cond;
+	CONDITION_VARIABLE queue_cond;
+	CONDITION_VARIABLE done_cond;
 #endif
 
 	/* needs rw access by worker and main thread */
diff --git a/lib/sqfs/data_writer/windows.c b/lib/sqfs/data_writer/windows.c
index b0459a5..0f1bef1 100644
--- a/lib/sqfs/data_writer/windows.c
+++ b/lib/sqfs/data_writer/windows.c
@@ -25,13 +25,12 @@ static DWORD WINAPI worker_proc(LPVOID arg)
 		EnterCriticalSection(&shared->mtx);
 		if (blk != NULL) {
 			data_writer_store_done(shared, blk, status);
-			SetEvent(shared->done_cond);
+			WakeConditionVariable(&shared->done_cond);
 		}
 
 		while (shared->queue == NULL && shared->status == 0) {
-			LeaveCriticalSection(&shared->mtx);
-			WaitForSingleObject(shared->queue_cond, INFINITE);
-			EnterCriticalSection(&shared->mtx);
+			SleepConditionVariableCS(&shared->queue_cond,
+						 &shared->mtx, INFINITE);
 		}
 
 		blk = data_writer_next_work_item(shared);
@@ -67,14 +66,8 @@ sqfs_data_writer_t *sqfs_data_writer_create(size_t max_block_size,
 		return NULL;
 
 	InitializeCriticalSection(&proc->mtx);
-
-	proc->queue_cond = CreateEvent(NULL, FALSE, FALSE, NULL);
-	if (proc->queue_cond == NULL)
-		goto fail;
-
-	proc->done_cond = CreateEvent(NULL, FALSE, FALSE, NULL);
-	if (proc->done_cond == NULL)
-		goto fail;
+	InitializeConditionVariable(&proc->queue_cond);
+	InitializeConditionVariable(&proc->done_cond);
 
 	if (data_writer_init(proc, max_block_size, cmp, num_workers,
 			     max_backlog, devblksz, file)) {
@@ -112,8 +105,7 @@ void sqfs_data_writer_destroy(sqfs_data_writer_t *proc)
 
 	EnterCriticalSection(&proc->mtx);
 	proc->status = -1;
-	if (proc->queue_cond != NULL)
-		SetEvent(proc->queue_cond);
+	WakeAllConditionVariable(&proc->queue_cond);
 	LeaveCriticalSection(&proc->mtx);
 
 	for (i = 0; i < proc->num_workers; ++i) {
@@ -131,12 +123,6 @@ void sqfs_data_writer_destroy(sqfs_data_writer_t *proc)
 		free(proc->workers[i]);
 	}
 
-	if (proc->queue_cond != NULL)
-		CloseHandle(proc->queue_cond);
-
-	if (proc->queue_cond != NULL)
-		CloseHandle(proc->done_cond);
-
 	DeleteCriticalSection(&proc->mtx);
 	data_writer_cleanup(proc);
 }
@@ -154,7 +140,7 @@ static void append_to_work_queue(sqfs_data_writer_t *proc,
 	block->sequence_number = proc->enqueue_id++;
 	block->next = NULL;
 	proc->backlog += 1;
-	SetEvent(proc->queue_cond);
+	WakeAllConditionVariable(&proc->queue_cond);
 }
 
 static sqfs_block_t *try_dequeue(sqfs_data_writer_t *proc)
@@ -231,7 +217,7 @@ static int process_done_queue(sqfs_data_writer_t *proc, sqfs_block_t *queue)
 
 				proc->backlog += 1;
 				proc->done = queue_merge(queue, proc->done);
-				SetEvent(proc->queue_cond);
+				WakeAllConditionVariable(&proc->queue_cond);
 				LeaveCriticalSection(&proc->mtx);
 
 				queue = NULL;
@@ -257,7 +243,7 @@ int test_and_set_status(sqfs_data_writer_t *proc, int status)
 	} else {
 		status = proc->status;
 	}
-	SetEvent(proc->queue_cond);
+	WakeAllConditionVariable(&proc->queue_cond);
 	LeaveCriticalSection(&proc->mtx);
 	return status;
 }
@@ -269,9 +255,8 @@ int data_writer_enqueue(sqfs_data_writer_t *proc, sqfs_block_t *block)
 
 	EnterCriticalSection(&proc->mtx);
 	while (proc->backlog > proc->max_backlog && proc->status == 0) {
-		LeaveCriticalSection(&proc->mtx);
-		WaitForSingleObject(proc->done_cond, INFINITE);
-		EnterCriticalSection(&proc->mtx);
+		SleepConditionVariableCS(&proc->done_cond, &proc->mtx,
+					 INFINITE);
 	}
 
 	if (proc->status != 0) {
@@ -300,9 +285,8 @@ int sqfs_data_writer_finish(sqfs_data_writer_t *proc)
 	for (;;) {
 		EnterCriticalSection(&proc->mtx);
 		while (proc->backlog > 0 && proc->status == 0) {
-			LeaveCriticalSection(&proc->mtx);
-			WaitForSingleObject(proc->done_cond, INFINITE);
-			EnterCriticalSection(&proc->mtx);
+			SleepConditionVariableCS(&proc->done_cond, &proc->mtx,
+						 INFINITE);
 		}
 
 		if (proc->status != 0) {