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

@@ -5,33 +5,29 @@
 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
+	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
+	INFINITE = 0xffffffff
-    WOKEN  = u32(16) // Woken mutex
-    ABOND  = u32(32)
-    BROKEN = u32(64)
-    DESTROYED = u32(0)
-)
-
-const (
-    INFINITY = 0xffffffff
 )
 
 // Ref - https://docs.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-waitforsingleobject#return-value
@@ -45,51 +41,35 @@ const (
 
 pub fn (m mut Mutex) lock() {
 	// if mutex handle not initalized
-    if m.mx == MHANDLE(0) {
+	if isnil(m.mx) {
 		m.mx = C.CreateMutex(0, false, 0)
-        _pmhx := int(m.mx)
+		if isnil(m.mx) {
-        if (((_pmhx & 0xff) - 1) == 0) || (_pmhx == os.INVALID_HANDLE_VALUE) {
+			m.state = .broken // handle broken and mutex state are broken
-            m.wstate = BROKEN // handle broken and mutex state are broken
 			return
 		}
 	}
-    state := C.WaitForSingleObject(m.mx, INFINITY) // infinity wait
+	state := C.WaitForSingleObject(m.mx, INFINITE) // infinite wait
-    // for {
+	m.state = match state {
-    //     if (m.cycle_woken - 1) < 0 {
+		WAIT_ABANDONED => { MutexState.abandoned }
-    //         break
+		WAIT_OBJECT_0  => { MutexState.waiting }
-    //     }
+		else           => { MutexState.broken }
-    //     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
 }
 
 pub fn (m mut Mutex) unlock() {
-    _pmx := &m.mx
+	if m.state == .waiting {
-    if _pmx != os.INVALID_HANDLE_VALUE {
+		if C.ReleaseMutex(m.mx) != 0 {
-        if m.wstate == (WAIT & u32(0xff)) {
+			m.state = .broken
-            if C.ReleaseMutex(_pmx) != 0 {
-                m.wstate = WOKEN // woken up mutex
-                return
-            }
-            m.wstate = ABOND
 			return
 		}
 	}
-    m.wstate = BROKEN
+	m.state = .released
 }
 
 pub fn (m mut Mutex) destroy() {
-    if m.wstate == WAIT {
+	if m.state == .waiting {
 		m.unlock() // unlock mutex before destroying
 	}
-    m.wstate = DESTROYED // setting up reference to invalid state
 	C.CloseHandle(m.mx)  // destroy mutex
+	m.state = .destroyed // setting up reference to invalid state
 }

vlib/sync/waitgroup.v

@@ -7,23 +7,16 @@ module sync
 struct WaitGroup {
 mut:
 	mu Mutex
-    finished Mutex
 	active int
 }
 
 pub fn (wg mut WaitGroup) add(delta int) {
 	wg.mu.lock()
-    if wg.active == 0 {
-        wg.finished.lock()
-    }
 	wg.active += delta
+	wg.mu.unlock()
 	if wg.active < 0 {
 		panic('Negative number of jobs in waitgroup')
 	}
-    if wg.active == 0 {
-        wg.finished.unlock()
-    }
-    wg.mu.unlock()
 }
 
 pub fn (wg mut WaitGroup) done() {
@@ -31,7 +24,8 @@ pub fn (wg mut WaitGroup) done() {
 }
 
 pub fn (wg mut WaitGroup) wait() {
-    wg.finished.lock()
+	for wg.active > 0 {
-    wg.finished.unlock()
+		// waiting
+	}
 }