sync: fix mutex on win & waitgroup (all os) update. fixes news_fetcher example on win (#1776)

examples/news_fetcher.v

@@ -25,15 +25,14 @@ mut:
 
 fn (f mut Fetcher) fetch() {
 	for {
-		f.mu.lock()
 		if f.cursor >= f.ids.len {
-			f.mu.unlock()
 			return
 		}
 		id := f.ids[f.cursor]
+		f.mu.lock()
 		f.cursor++
-		cursor := f.cursor
 		f.mu.unlock()
+		cursor := f.cursor
 		resp := http.get('https://hacker-news.firebaseio.com/v0/item/${id}.json') or {
 			println('failed to fetch data from /v0/item/${id}.json')
 			exit(1)
@@ -42,8 +41,8 @@ fn (f mut Fetcher) fetch() {
 			println('failed to decode a story')
 			exit(1)
 		}
-		f.wg.done()
 		println('#$cursor) $story.title | $story.url')
+		f.wg.done()
 	}
 }
 

vlib/sync/sync_win.v

@@ -5,91 +5,71 @@
 module sync
 import os
 
-// Unsafe pointer
-type Pointer voidptr
-
 // Mutex HANDLE
 type MHANDLE voidptr
 
 struct Mutex {
 mut:
-    mx           MHANDLE // mutex handle
-    wstate       u32     // wait state
-    cycle_wait   i64     // waiting cycles (implemented only with atomic)
-    cycle_woken  i64     // woken cycles    ^
-    reader_sem   u32     // reader semarphone
-    writer_sem   u32     // writer semaphones
+	mx           MHANDLE    // mutex handle
+	state        MutexState // mutex state
+	cycle_wait   i64        // waiting cycles (implemented only with atomic)
+	cycle_woken  i64        // woken cycles    ^
+	reader_sem   u32        // reader semarphone
+	writer_sem   u32        // writer semaphones
 }
 
+enum MutexState {
+	broken
+	waiting
+	released
+	abandoned
+	destroyed
+}
 
 const (
-    WAIT   = u32(8)  // Waiting mutex
-    WOKEN  = u32(16) // Woken mutex
-    ABOND  = u32(32)
-    BROKEN = u32(64)
-    DESTROYED = u32(0)
-)
-
-const (
-    INFINITY = 0xffffffff
+	INFINITE = 0xffffffff
 )
 
 // Ref - https://docs.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-waitforsingleobject#return-value
 const (
-    WAIT_ABANDONED     = 0x00000080
-    WAIT_IO_COMPLETION = 0x000000C0
-    WAIT_OBJECT_0      = 0x00000000
-    WAIT_TIMEOUT       = 0x00000102
-    WAIT_FAILED        = 0xFFFFFFFF
+	WAIT_ABANDONED     = 0x00000080
+	WAIT_IO_COMPLETION = 0x000000C0
+	WAIT_OBJECT_0      = 0x00000000
+	WAIT_TIMEOUT       = 0x00000102
+	WAIT_FAILED        = 0xFFFFFFFF
 )
 
 pub fn (m mut Mutex) lock() {
-    // if mutex handle not initalized
-    if m.mx == MHANDLE(0) {
-        m.mx = C.CreateMutex(0, false, 0)
-        _pmhx := int(m.mx)
-        if (((_pmhx & 0xff) - 1) == 0) || (_pmhx == os.INVALID_HANDLE_VALUE) {
-            m.wstate = BROKEN // handle broken and mutex state are broken
-            return
-        }
-    }
-    state := C.WaitForSingleObject(m.mx, INFINITY) // infinity wait
-    // for {
-    //     if (m.cycle_woken - 1) < 0 {
-    //         break
-    //     }
-    //     if state&0x00000080 {
-    //         continue // abondoned
-    //     }
-    //     m.cycle_wait++
-    // }
-    match state {
-        WAIT_FAILED    => { m.wstate = BROKEN }
-        WAIT_ABANDONED => { m.wstate = ABOND }
-        WAIT_OBJECT_0  => { m.wstate = WAIT & u32(0xff) }
-    }
-    // todo implement atomic counter
+	// if mutex handle not initalized
+	if isnil(m.mx) {
+		m.mx = C.CreateMutex(0, false, 0)
+		if isnil(m.mx) {
+			m.state = .broken // handle broken and mutex state are broken
+			return
+		}
+	}
+	state := C.WaitForSingleObject(m.mx, INFINITE) // infinite wait
+	m.state = match state {
+		WAIT_ABANDONED => { MutexState.abandoned }
+		WAIT_OBJECT_0  => { MutexState.waiting }
+		else           => { MutexState.broken }
+	}
 }
 
 pub fn (m mut Mutex) unlock() {
-    _pmx := &m.mx
-    if _pmx != os.INVALID_HANDLE_VALUE {
-        if m.wstate == (WAIT & u32(0xff)) {
-            if C.ReleaseMutex(_pmx) != 0 {
-                m.wstate = WOKEN // woken up mutex
-                return
-            }
-            m.wstate = ABOND
-            return
-        }
-    }
-    m.wstate = BROKEN
+	if m.state == .waiting {
+		if C.ReleaseMutex(m.mx) != 0 {
+			m.state = .broken
+			return
+		}
+	}
+	m.state = .released
 }
 
 pub fn (m mut Mutex) destroy() {
-    if m.wstate == WAIT {
-        m.unlock() // unlock mutex before destroying
-    }
-    m.wstate = DESTROYED // setting up reference to invalid state
-    C.CloseHandle(m.mx) // destroy mutex
+	if m.state == .waiting {
+		m.unlock() // unlock mutex before destroying
+	}
+	C.CloseHandle(m.mx)  // destroy mutex
+	m.state = .destroyed // setting up reference to invalid state
 }

vlib/sync/waitgroup.v

@@ -6,32 +6,26 @@ module sync
 
 struct WaitGroup {
 mut:
-    mu Mutex
-    finished Mutex
-    active int
+	mu Mutex
+	active int
 }
 
 pub fn (wg mut WaitGroup) add(delta int) {
-    wg.mu.lock()
-    if wg.active == 0 {
-        wg.finished.lock()
-    }
-    wg.active += delta
-    if wg.active < 0 {
-        panic('Negative number of jobs in waitgroup')
-    }
-    if wg.active == 0 {
-        wg.finished.unlock()
-    }
-    wg.mu.unlock()
+	wg.mu.lock()
+	wg.active += delta
+	wg.mu.unlock()
+	if wg.active < 0 {
+		panic('Negative number of jobs in waitgroup')
+	}
 }
 
 pub fn (wg mut WaitGroup) done() {
-    wg.add(-1)
+	wg.add(-1)
 }
 
 pub fn (wg mut WaitGroup) wait() {
-    wg.finished.lock()
-    wg.finished.unlock()
+	for wg.active > 0 {
+		// waiting
+	}
 }