diff --git a/cmd/tools/modules/testing/common.v b/cmd/tools/modules/testing/common.v
index f350582364..cd20ba80a1 100644
--- a/cmd/tools/modules/testing/common.v
+++ b/cmd/tools/modules/testing/common.v
@@ -28,7 +28,7 @@ pub mut:
 }
 
 pub fn (mut mh TestMessageHandler) append_message(msg string) {
-	mh.mtx.lock()
+	mh.mtx.m_lock()
 	mh.messages << msg
 	mh.mtx.unlock()
 }
@@ -102,7 +102,7 @@ pub fn (mut ts TestSession) test() {
 }
 
 pub fn (mut m TestMessageHandler) display_message() {
-	m.mtx.lock()
+	m.mtx.m_lock()
 	defer {
 		m.messages.clear()
 		m.mtx.unlock()
diff --git a/cmd/tools/preludes/live_shared.v b/cmd/tools/preludes/live_shared.v
index 0e23bfad75..bdabb0d492 100644
--- a/cmd/tools/preludes/live_shared.v
+++ b/cmd/tools/preludes/live_shared.v
@@ -2,8 +2,8 @@ module main
 
 // This prelude is loaded in every v program compiled with -live,
 // but only for the shared library.
-import live.shared
+import live.sharedlib
 
 const (
-	no_warning_live_shared_is_used = shared.is_used
+	no_warning_live_shared_is_used = sharedlib.is_used
 )
diff --git a/doc/docs.md b/doc/docs.md
index 7e10aac02c..ac1915ec64 100644
--- a/doc/docs.md
+++ b/doc/docs.md
@@ -1390,7 +1390,7 @@ mut:
 
 fn (mut b St) g() {
 	...
-	b.mtx.lock()
+	b.mtx.m_lock()
 	// read/modify/write b.x
 	...
 	b.mtx.unlock()
@@ -1404,7 +1404,7 @@ fn caller() {
 	}
 	go a.g()
 	...
-	a.mtx.lock()
+	a.mtx.m_lock()
 	// read/modify/write a.x
 	...
 	a.mtx.unlock()
diff --git a/vlib/clipboard/clipboard_linux.c.v b/vlib/clipboard/clipboard_linux.c.v
index 564e56b754..ea1cdf60d2 100644
--- a/vlib/clipboard/clipboard_linux.c.v
+++ b/vlib/clipboard/clipboard_linux.c.v
@@ -181,7 +181,7 @@ fn (mut cb Clipboard) free() {
 }
 
 fn (mut cb Clipboard) clear(){
-	cb.mutex.lock()
+	cb.mutex.m_lock()
 	C.XSetSelectionOwner(cb.display, cb.selection, C.Window(C.None), C.CurrentTime)
 	C.XFlush(cb.display)
 	cb.is_owner = false
@@ -200,7 +200,7 @@ fn (cb &Clipboard) take_ownership(){
 
 fn (mut cb Clipboard) set_text(text string) bool {
 	if cb.window == C.Window(C.None) {return false}
-	cb.mutex.lock()
+	cb.mutex.m_lock()
 	cb.text = text
 	cb.is_owner = true
 	cb.take_ownership()
@@ -238,7 +238,7 @@ fn (mut cb Clipboard) transmit_selection(xse &C.XSelectionEvent) bool {
 		targets := cb.get_supported_targets()
 		C.XChangeProperty(xse.display, xse.requestor, xse.property, cb.get_atom(.xa_atom), 32, C.PropModeReplace, targets.data, targets.len)
 	} else if cb.is_supported_target(xse.target) && cb.is_owner && cb.text != "" {
-		cb.mutex.lock()
+		cb.mutex.m_lock()
 		C.XChangeProperty(xse.display, xse.requestor, xse.property, xse.target, 8, C.PropModeReplace, cb.text.str, cb.text.len)
 		cb.mutex.unlock()
 	} else {
@@ -265,7 +265,7 @@ fn (mut cb Clipboard) start_listener(){
 			}
 			C.SelectionClear {
 				if event.xselectionclear.window == cb.window && event.xselectionclear.selection == cb.selection {
-					cb.mutex.lock()
+					cb.mutex.m_lock()
 					cb.is_owner = false
 					cb.text = ""
 					cb.mutex.unlock()
@@ -304,7 +304,7 @@ fn (mut cb Clipboard) start_listener(){
 					} else if event.xselection.target == to_be_requested {
 						sent_request = false
 						to_be_requested = C.Atom(0)
-						cb.mutex.lock()
+						cb.mutex.m_lock()
 						prop := read_property(event.xselection.display, event.xselection.requestor, event.xselection.property)
 						C.XDeleteProperty(event.xselection.display, event.xselection.requestor, event.xselection.property)
 						if cb.is_supported_target(prop.actual_type) {
diff --git a/vlib/live/shared/live_sharedlib.v b/vlib/live/sharedlib/live_sharedlib.v
similarity index 70%
rename from vlib/live/shared/live_sharedlib.v
rename to vlib/live/sharedlib/live_sharedlib.v
index 8ee31de31a..471d28e6b9 100644
--- a/vlib/live/shared/live_sharedlib.v
+++ b/vlib/live/sharedlib/live_sharedlib.v
@@ -1,4 +1,4 @@
-module shared
+module sharedlib
 
 import live
 
diff --git a/vlib/net/websocket/io.v b/vlib/net/websocket/io.v
index 4aaac8d934..0666fd0b20 100644
--- a/vlib/net/websocket/io.v
+++ b/vlib/net/websocket/io.v
@@ -2,7 +2,7 @@ module websocket
 
 fn (mut ws Client) write_to_server(buf voidptr, len int) int {
 	mut bytes_written := 0
-	ws.write_lock.lock()
+	ws.write_lock.m_lock()
 	bytes_written = if ws.is_ssl {
 		C.SSL_write(ws.ssl, buf, len)
 	} else {
diff --git a/vlib/net/websocket/ws.v b/vlib/net/websocket/ws.v
index c8fe42e52e..124a893aab 100644
--- a/vlib/net/websocket/ws.v
+++ b/vlib/net/websocket/ws.v
@@ -19,7 +19,7 @@ pub struct Client {
 	// cwebsocket_subprotocol *subprotocol;
 	// cwebsocket_subprotocol *subprotocols[];
 mut:
-	lock       &sync.Mutex = sync.new_mutex()
+	mtx        &sync.Mutex = sync.new_mutex()
 	write_lock &sync.Mutex = sync.new_mutex()
 	state      State
 	socket     net.Socket
@@ -132,9 +132,9 @@ pub fn (mut ws Client) connect() int {
 			// do nothing
 		}
 	}
-	ws.lock.lock()
+	ws.mtx.m_lock()
 	ws.state = .connecting
-	ws.lock.unlock()
+	ws.mtx.unlock()
 	uri := ws.parse_uri()
 	nonce := get_nonce(ws.nonce_size)
 	seckey := base64.encode(nonce)
@@ -160,17 +160,17 @@ pub fn (mut ws Client) connect() int {
 	if ws.is_ssl {
 		ws.connect_ssl()
 	}
-	ws.lock.lock()
+	ws.mtx.m_lock()
 	ws.state = .connected
-	ws.lock.unlock()
+	ws.mtx.unlock()
 	res := ws.write_to_server(handshake.str, handshake.len)
 	if res <= 0 {
 		l.f('Handshake failed.')
 	}
 	ws.read_handshake(seckey)
-	ws.lock.lock()
+	ws.mtx.m_lock()
 	ws.state = .open
-	ws.lock.unlock()
+	ws.mtx.unlock()
 	ws.send_open_event()
 	unsafe {
 		handshake.free()
@@ -182,9 +182,9 @@ pub fn (mut ws Client) connect() int {
 
 pub fn (mut ws Client) close(code int, message string) {
 	if ws.state != .closed && ws.socket.sockfd > 1 {
-		ws.lock.lock()
+		ws.mtx.m_lock()
 		ws.state = .closing
-		ws.lock.unlock()
+		ws.mtx.unlock()
 		mut code32 := 0
 		if code > 0 {
 			code_ := C.htons(code)
@@ -223,9 +223,9 @@ pub fn (mut ws Client) close(code int, message string) {
 		}
 		ws.fragments = []
 		ws.send_close_event()
-		ws.lock.lock()
+		ws.mtx.m_lock()
 		ws.state = .closed
-		ws.lock.unlock()
+		ws.mtx.unlock()
 		unsafe {
 		}
 		// TODO impl autoreconnect
diff --git a/vlib/sync/pool.v b/vlib/sync/pool.v
index 90ec0db8d6..65eced2dfc 100644
--- a/vlib/sync/pool.v
+++ b/vlib/sync/pool.v
@@ -139,7 +139,7 @@ fn process_in_thread(mut pool PoolProcessor, task_id int) {
 		if pool.ntask >= ilen {
 			break
 		}
-		pool.ntask_mtx.lock()
+		pool.ntask_mtx.m_lock()
 		idx = pool.ntask
 		pool.ntask++
 		pool.ntask_mtx.unlock()
diff --git a/vlib/sync/sync_nix.c.v b/vlib/sync/sync_nix.c.v
index 341a0b4245..ff5fbe6959 100644
--- a/vlib/sync/sync_nix.c.v
+++ b/vlib/sync/sync_nix.c.v
@@ -17,7 +17,8 @@ pub fn new_mutex() &Mutex {
 	return m
 }
 
-pub fn (mut m Mutex) lock() {
+// m_lock(), for *manual* mutex handling, since `lock` is a keyword
+pub fn (mut m Mutex) m_lock() {
 	C.pthread_mutex_lock(&m.mutex)
 }
 
diff --git a/vlib/sync/sync_windows.c.v b/vlib/sync/sync_windows.c.v
index e4da37a2dc..88a57c6bda 100644
--- a/vlib/sync/sync_windows.c.v
+++ b/vlib/sync/sync_windows.c.v
@@ -43,7 +43,7 @@ pub fn new_mutex() &Mutex {
 	return sm
 }
 
-pub fn (mut m Mutex) lock() {
+pub fn (mut m Mutex) m_lock() {
 	// if mutex handle not initalized
 	if isnil(m.mx) {
 		m.mx = MHANDLE(C.CreateMutex(0, false, 0))
diff --git a/vlib/sync/waiter_nix.c.v b/vlib/sync/waiter_nix.c.v
index 80344e34da..9c2a4b841d 100644
--- a/vlib/sync/waiter_nix.c.v
+++ b/vlib/sync/waiter_nix.c.v
@@ -10,7 +10,7 @@ mut:
 }
 
 pub fn (mut w Waiter) wait() {
-	w.mx.lock()
+	w.mx.m_lock()
 }
 
 pub fn (mut w Waiter) stop() {
diff --git a/vlib/sync/waitgroup.v b/vlib/sync/waitgroup.v
index 4963cd2d1f..29bca0b691 100644
--- a/vlib/sync/waitgroup.v
+++ b/vlib/sync/waitgroup.v
@@ -30,7 +30,7 @@ pub fn new_waitgroup() &WaitGroup {
 // add panics if task count drops below zero.
 pub fn (mut wg WaitGroup) add(delta int) {
 	// protect task_count
-	wg.task_count_mutex.lock()
+	wg.task_count_mutex.m_lock()
 	defer {
 		wg.task_count_mutex.unlock()
 	}
diff --git a/vlib/v/ast/ast.v b/vlib/v/ast/ast.v
index a734b88b96..4e39ec8c22 100644
--- a/vlib/v/ast/ast.v
+++ b/vlib/v/ast/ast.v
@@ -11,7 +11,7 @@ pub type TypeDecl = AliasTypeDecl | FnTypeDecl | SumTypeDecl
 
 pub type Expr = AnonFn | ArrayInit | AsCast | Assoc | BoolLiteral | CallExpr | CastExpr |
 	CharLiteral | ComptimeCall | ConcatExpr | EnumVal | FloatLiteral | Ident | IfExpr | IfGuardExpr |
-	IndexExpr | InfixExpr | IntegerLiteral | Likely | MapInit | MatchExpr | None | OrExpr |
+	IndexExpr | InfixExpr | IntegerLiteral | Likely | LockExpr | MapInit | MatchExpr | None | OrExpr |
 	ParExpr | PostfixExpr | PrefixExpr | RangeExpr | SelectorExpr | SizeOf | SqlExpr | StringInterLiteral |
 	StringLiteral | StructInit | Type | TypeOf
 
@@ -232,6 +232,7 @@ pub:
 	receiver_pos  token.Position
 	is_method     bool
 	rec_mut       bool // is receiver mutable
+	rec_share     table.ShareType
 	language      table.Language
 	no_body       bool // just a definition `fn C.malloc()`
 	is_builtin    bool // this function is defined in builtin/strconv
@@ -271,6 +272,7 @@ pub mut:
 pub struct CallArg {
 pub:
 	is_mut bool
+	share  table.ShareType
 	expr   Expr
 pub mut:
 	typ    table.Type
@@ -301,6 +303,7 @@ pub struct Var {
 pub:
 	name       string
 	expr       Expr
+	share      table.ShareType
 	is_mut     bool
 	is_arg     bool // fn args should not be autofreed
 pub mut:
@@ -344,6 +347,7 @@ pub mut:
 	is_mut      bool
 	is_static   bool
 	is_optional bool
+	share       table.ShareType
 }
 
 pub type IdentInfo = IdentFn | IdentVar
@@ -438,6 +442,18 @@ pub:
 	comment Comment
 }
 
+pub struct LockExpr {
+pub:
+	stmts    []Stmt
+	is_rlock bool
+	pos      token.Position
+pub mut:
+	lockeds  []Ident // `x`, `y` in `lock x, y {`
+	is_expr  bool
+	is_rw    bool // `rwshared` needs special special handling even in `lock` case
+	typ      table.Type
+}
+
 pub struct MatchExpr {
 pub:
 	tok_kind      token.Kind
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index b6ae67899d..0bb0a6d412 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -1128,12 +1128,39 @@ pub fn (mut c Checker) call_fn(mut call_expr ast.CallExpr) table.Type {
 		}
 		if call_arg.is_mut {
 			c.fail_if_immutable(call_arg.expr)
+
 			if !arg.is_mut {
-				c.error('`$arg.name` argument is not mutable, `mut` is not needed`', call_arg.expr.position())
+				mut words := 'mutable'
+				mut tok := 'mut'
+				if call_arg.share == .shared_t {
+					words = 'shared'
+					tok = 'shared'
+				} else if call_arg.share == .rwshared_t {
+					words = 'read/write shared'
+					tok = 'rwshared'
+				} else if call_arg.share == .atomic_t {
+					words = 'atomic'
+					tok = 'atomic'
+				}
+				c.error('`$arg.name` argument is not $words, `$tok` is not needed`', call_arg.expr.position())
+			} else if arg.typ.share() != call_arg.share {
+				c.error('wrong shared type', call_arg.expr.position())
 			}
 		} else {
-			if arg.is_mut {
-				c.error('`$arg.name` is a mutable argument, you need to provide `mut`: `${call_expr.name}(mut ...)`',
+			if arg.is_mut && (!call_arg.is_mut || arg.typ.share() != call_arg.share) {
+				mut words := ' mutable'
+				mut tok := 'mut'
+				if arg.typ.share() == .shared_t {
+					words = ' shared'
+					tok = 'shared'
+				} else if arg.typ.share() == .rwshared_t {
+					words = ' read/write shared'
+					tok = 'rwshared'
+				} else if arg.typ.share() == .atomic_t {
+					words = 'n atomic'
+					tok = 'atomic'
+				}
+				c.error('`$arg.name` is a$words argument, you need to provide `$tok`: `${call_expr.name}($tok ...)`',
 					call_arg.expr.position())
 			}
 		}
@@ -1497,6 +1524,13 @@ pub fn (mut c Checker) assign_stmt(mut assign_stmt ast.AssignStmt) {
 					}
 					mut scope := c.file.scope.innermost(assign_stmt.pos.pos)
 					mut ident_var_info := left.var_info()
+					if ident_var_info.share in [.shared_t, .rwshared_t] {
+						left_type = left_type.set_flag(.shared_f)
+					}
+					if ident_var_info.share in [.atomic_t, .rwshared_t] {
+						left_type = left_type.set_flag(.atomic_or_rw)
+					}
+					assign_stmt.left_types[i] = left_type
 					ident_var_info.typ = left_type
 					left.info = ident_var_info
 					scope.update_var_type(left.name, left_type)
@@ -2116,6 +2150,9 @@ pub fn (mut c Checker) expr(node ast.Expr) table.Type {
 		ast.IntegerLiteral {
 			return table.any_int_type
 		}
+		ast.LockExpr {
+			return c.lock_expr(mut node)
+		}
 		ast.MapInit {
 			return c.map_init(mut node)
 		}
@@ -2494,6 +2531,15 @@ fn (mut c Checker) match_exprs(mut node ast.MatchExpr, type_sym table.TypeSymbol
 	c.error(err_details, node.pos)
 }
 
+pub fn (mut c Checker) lock_expr(mut node ast.LockExpr) table.Type {
+	for id in node.lockeds {
+		c.ident(mut id)
+	}
+	c.stmts(node.stmts)
+	// void for now... maybe sometime `x := lock a { a.getval() }`
+	return table.void_type
+}
+
 pub fn (mut c Checker) if_expr(mut node ast.IfExpr) table.Type {
 	mut expr_required := false
 	if c.expected_type != table.void_type {
diff --git a/vlib/v/fmt/fmt.v b/vlib/v/fmt/fmt.v
index b64d2560ff..5dcdd48a65 100644
--- a/vlib/v/fmt/fmt.v
+++ b/vlib/v/fmt/fmt.v
@@ -835,6 +835,9 @@ pub fn (mut f Fmt) expr(node ast.Expr) {
 		ast.IntegerLiteral {
 			f.write(node.val)
 		}
+		ast.LockExpr {
+			f.lock_expr(node) 
+		}
 		ast.MapInit {
 			if node.keys.len == 0 {
 				mut ktyp := node.key_type
@@ -1164,6 +1167,20 @@ pub fn (mut f Fmt) short_module(name string) string {
 	return '${aname}.$symname'
 }
 
+pub fn (mut f Fmt) lock_expr(lex ast.LockExpr) {
+	f.write('lock ')
+	for i, v in lex.lockeds {
+		if i > 0 {
+			f.write(', ')
+		}
+		f.expr(v)
+	}
+	f.write(' {')
+	f.writeln('')
+	f.stmts(lex.stmts)
+	f.write('}')
+}
+
 pub fn (mut f Fmt) if_expr(it ast.IfExpr) {
 	single_line := it.branches.len == 2 && it.has_else &&
 		it.branches[0].stmts.len == 1 && it.branches[1].stmts.len == 1 &&
diff --git a/vlib/v/gen/cgen.v b/vlib/v/gen/cgen.v
index 7f248afe22..e0e94ab871 100644
--- a/vlib/v/gen/cgen.v
+++ b/vlib/v/gen/cgen.v
@@ -58,7 +58,11 @@ mut:
 	is_array_set         bool
 	is_amp               bool // for `&Foo{}` to merge PrefixExpr `&` and StructInit `Foo{}`; also for `&byte(0)` etc
 	is_sql               bool // Inside `sql db{}` statement, generating sql instead of C (e.g. `and` instead of `&&` etc)
+	is_shared            bool // for initialization of hidden mutex in `[rw]shared` literals
+	is_rwshared          bool
 	optionals            []string // to avoid duplicates TODO perf, use map
+	shareds              []int // types with hidden mutex for which decl has been emitted
+	rwshareds            []int // same with hidden rwmutex
 	inside_ternary       int // ?: comma separated statements on a single line
 	inside_map_postfix   bool // inside map++/-- postfix expr
 	inside_map_infix     bool // inside map<</+=/-= infix expr
@@ -329,7 +333,11 @@ fn (g &Gen) typ(t table.Type) string {
 }
 
 fn (g &Gen) base_type(t table.Type) string {
-	mut styp := g.cc_type(t)
+	share := t.share()
+	mut styp := if share == .atomic_t { t.atomic_typename() } else { g.cc_type(t) }
+	if t.has_flag(.shared_f) {
+		styp = g.find_or_register_shared(t, styp)
+	}
 	nr_muls := t.nr_muls()
 	if nr_muls > 0 {
 		styp += strings.repeat(`*`, nr_muls)
@@ -386,6 +394,27 @@ fn (mut g Gen) register_optional(t table.Type) string {
 	return styp
 }
 
+fn (mut g Gen) find_or_register_shared(t table.Type, base string) string {
+	is_rw := t.has_flag(.atomic_or_rw)
+	prefix := if is_rw { 'rw' } else { '' }
+	sh_typ :=  '__${prefix}shared__$base'
+	t_idx := t.idx()
+	if (is_rw && t_idx in g.rwshareds) || (!is_rw && t_idx in g.shareds) {
+		return sh_typ
+	}
+	// TODO: These two should become different...
+	mtx_typ := if is_rw { 'sync__Mutex' } else { 'sync__Mutex' }
+	g.hotcode_definitions.writeln('struct $sh_typ { $base val; $mtx_typ* mtx; };')
+	g.typedefs2.writeln('typedef struct $sh_typ $sh_typ;')
+	// println('registered shared type $sh_typ')
+	if is_rw {
+		g.rwshareds << t_idx
+	} else {
+		g.shareds << t_idx
+	}
+	return sh_typ
+}
+
 // cc_type returns the Cleaned Concrete Type name, *without ptr*,
 // i.e. it's always just Cat, not Cat_ptr:
 fn (g &Gen) cc_type(t table.Type) string {
@@ -1141,7 +1170,7 @@ fn (mut g Gen) gen_assign_stmt(assign_stmt ast.AssignStmt) {
 	// `a := 1` | `a,b := 1,2`
 	for i, left in assign_stmt.left {
 		mut var_type := assign_stmt.left_types[i]
-		val_type := assign_stmt.right_types[i]
+		mut val_type := assign_stmt.right_types[i]
 		val := assign_stmt.right[i]
 		mut is_call := false
 		mut blank_assign := false
@@ -1151,6 +1180,15 @@ fn (mut g Gen) gen_assign_stmt(assign_stmt ast.AssignStmt) {
 			// id_info := ident.var_info()
 			// var_type = id_info.typ
 			blank_assign = ident.kind == .blank_ident
+			if ident.info is ast.IdentVar {
+				share := (ident.info as ast.IdentVar).share
+				if share in [.shared_t, .rwshared_t] {
+					var_type = var_type.set_flag(.shared_f)
+				}
+				if share in [.atomic_t, .rwshared_t] {
+					var_type = var_type.set_flag(.atomic_or_rw)
+				}
+			}
 		}
 		styp := g.typ(var_type)
 		mut is_fixed_array_init := false
@@ -1278,6 +1316,8 @@ fn (mut g Gen) gen_assign_stmt(assign_stmt ast.AssignStmt) {
 			if unwrap_optional {
 				g.write('*($styp*)')
 			}
+			g.is_shared = var_type.has_flag(.shared_f)
+			g.is_rwshared = var_type.has_flag(.atomic_or_rw)
 			if !cloned {
 				if is_decl {
 					if is_fixed_array_init && !has_val {
@@ -1303,6 +1343,8 @@ fn (mut g Gen) gen_assign_stmt(assign_stmt ast.AssignStmt) {
 				g.write(' })')
 				g.is_array_set = false
 			}
+			g.is_rwshared = false
+			g.is_shared = false
 		}
 		g.right_is_opt = false
 		g.is_assign_rhs = false
@@ -1622,6 +1664,9 @@ fn (mut g Gen) expr(node ast.Expr) {
 				g.write(node.val) // .int().str())
 			}
 		}
+		ast.LockExpr {
+			g.lock_expr(node)
+		}
 		ast.MatchExpr {
 			g.match_expr(node)
 		}
@@ -1721,6 +1766,9 @@ fn (mut g Gen) expr(node ast.Expr) {
 				// g.write('. /*typ=  $it.expr_type */') // ${g.typ(it.expr_type)} /')
 				g.write('.')
 			}
+			if node.expr_type.has_flag(.shared_f) {
+				g.write('val.')
+			}
 			if node.expr_type == 0 {
 				verror('cgen: SelectorExpr | expr_type: 0 | it.expr: `$node.expr` | field: `$node.field_name` | file: $g.file.path | line: $node.pos.line_nr')
 			}
@@ -2011,6 +2059,36 @@ fn (mut g Gen) infix_expr(node ast.InfixExpr) {
 	}
 }
 
+fn (mut g Gen) lock_expr(node ast.LockExpr) {
+	for id in node.lockeds {
+		name := id.name
+		deref := if id.is_mut { '->' } else { '.' }
+		// TODO: use 3 different locking functions
+		if node.is_rlock {
+			g.writeln('sync__Mutex_m_lock(${name}${deref}mtx);')
+		} else if id.var_info().typ.has_flag(.atomic_or_rw) {
+			g.writeln('sync__Mutex_m_lock(${name}${deref}mtx);')
+		} else {
+			g.writeln('sync__Mutex_m_lock(${name}${deref}mtx);')
+		}
+	}
+	g.stmts(node.stmts)
+	// unlock in reverse order
+	for i := node.lockeds.len-1; i >= 0; i-- {
+		id := node.lockeds[i]
+		name := id.name
+		deref := if id.is_mut { '->' } else { '.' }
+		// TODO: use 3 different unlocking functions
+		if node.is_rlock {
+			g.writeln('sync__Mutex_unlock(${name}${deref}mtx);')
+		} else if id.var_info().typ.has_flag(.atomic_or_rw) {
+			g.writeln('sync__Mutex_unlock(${name}${deref}mtx);')
+		} else {
+			g.writeln('sync__Mutex_unlock(${name}${deref}mtx);')
+		}
+	}
+}
+
 fn (mut g Gen) match_expr(node ast.MatchExpr) {
 	// println('match expr typ=$it.expr_type')
 	// TODO
@@ -2150,6 +2228,10 @@ fn (mut g Gen) ident(node ast.Ident) {
 			g.write('(*($styp*)${name}.data)')
 			return
 		}
+		if !g.is_assign_lhs && (ident_var.share == .shared_t || ident_var.share == .rwshared_t) {
+			g.write('${name}.val')
+			return
+		}
 	}
 	g.write(g.get_ternary_name(name))
 }
@@ -2671,6 +2753,7 @@ const (
 
 fn (mut g Gen) struct_init(struct_init ast.StructInit) {
 	styp := g.typ(struct_init.typ)
+	mut shared_styp := '' // only needed for shared &St{...
 	if styp in skip_struct_init {
 		g.go_back_out(3)
 		return
@@ -2680,9 +2763,22 @@ fn (mut g Gen) struct_init(struct_init ast.StructInit) {
 	g.is_amp = false // reset the flag immediately so that other struct inits in this expr are handled correctly
 	if is_amp {
 		g.out.go_back(1) // delete the `&` already generated in `prefix_expr()
-		g.write('($styp*)memdup(&($styp){')
+		if g.is_shared {
+			mut shared_typ := struct_init.typ.set_flag(.shared_f)
+			if g.is_rwshared {
+				shared_typ = shared_typ.set_flag(.atomic_or_rw)
+			}
+			shared_styp = g.typ(shared_typ)
+			g.writeln('($shared_styp*)memdup(&($shared_styp){.val = ($styp){')
+		} else {
+			g.write('($styp*)memdup(&($styp){')
+		}
 	} else {
-		g.writeln('($styp){')
+		if g.is_shared {
+			g.writeln('{.val = {')
+		} else {
+			g.writeln('($styp){')
+		}
 	}
 	// mut fields := []string{}
 	mut inited_fields := map[string]int{} // TODO this is done in checker, move to ast node
@@ -2771,7 +2867,12 @@ fn (mut g Gen) struct_init(struct_init ast.StructInit) {
 		g.write('\n#ifndef __cplusplus\n0\n#endif\n')
 	}
 	g.write('}')
-	if is_amp {
+	if g.is_shared {
+		g.write(', .mtx = sync__new_mutex()}')
+		if is_amp {
+			g.write(', sizeof($shared_styp))')
+		}
+	} else if is_amp {
 		g.write(', sizeof($styp))')
 	}
 }
diff --git a/vlib/v/gen/js/js.v b/vlib/v/gen/js/js.v
index b3903ff89d..1459a6c439 100644
--- a/vlib/v/gen/js/js.v
+++ b/vlib/v/gen/js/js.v
@@ -563,6 +563,9 @@ fn (mut g JsGen) expr(node ast.Expr) {
 		ast.IntegerLiteral {
 			g.write(it.val)
 		}
+		ast.LockExpr {
+			g.gen_lock_expr(it)
+		}
 		ast.MapInit {
 			g.gen_map_init_expr(it)
 		}
@@ -1192,6 +1195,10 @@ fn (mut g JsGen) gen_ident(node ast.Ident) {
 	g.write(name)
 }
 
+fn (mut g JsGen) gen_lock_expr(node ast.LockExpr) {
+	// TODO: implement this
+}
+
 fn (mut g JsGen) gen_if_expr(node ast.IfExpr) {
 	type_sym := g.table.get_type_symbol(node.typ)
 
diff --git a/vlib/v/parser/assign.v b/vlib/v/parser/assign.v
index 4166b1ed6a..e34b96bc73 100644
--- a/vlib/v/parser/assign.v
+++ b/vlib/v/parser/assign.v
@@ -4,6 +4,7 @@
 module parser
 
 import v.ast
+import v.table
 
 fn (mut p Parser) assign_stmt() ast.Stmt {
 	return p.partial_assign_stmt(p.expr_list())
@@ -106,16 +107,22 @@ fn (mut p Parser) partial_assign_stmt(left []ast.Expr) ast.Stmt {
 					if p.scope.known_var(lx.name) {
 						p.error_with_pos('redefinition of `$lx.name`', lx.pos)
 					}
+					mut share := table.ShareType(0)
+					if lx.info is ast.IdentVar {
+						share = (lx.info as ast.IdentVar).share
+					}
 					if left.len == right.len {
 						p.scope.register(lx.name, ast.Var{
 							name: lx.name
 							expr: right[i]
+							share: share
 							is_mut: lx.is_mut || p.inside_for
 							pos: lx.pos
 						})
 					} else {
 						p.scope.register(lx.name, ast.Var{
 							name: lx.name
+							share: share
 							is_mut: lx.is_mut || p.inside_for
 							pos: lx.pos
 						})
diff --git a/vlib/v/parser/fn.v b/vlib/v/parser/fn.v
index e938b169da..9b35c9c8a2 100644
--- a/vlib/v/parser/fn.v
+++ b/vlib/v/parser/fn.v
@@ -100,14 +100,16 @@ pub fn (mut p Parser) call_expr(language table.Language, mod string) ast.CallExp
 pub fn (mut p Parser) call_args() []ast.CallArg {
 	mut args := []ast.CallArg{}
 	for p.tok.kind != .rpar {
-		mut is_mut := false
-		if p.tok.kind == .key_mut {
+		is_shared := p.tok.kind in [.key_shared, .key_rwshared]
+		is_atomic_or_rw := p.tok.kind in [.key_rwshared, .key_atomic]
+		is_mut := p.tok.kind == .key_mut || is_shared || is_atomic_or_rw
+		if is_mut {
 			p.next()
-			is_mut = true
 		}
 		e := p.expr(0)
 		args << ast.CallArg{
 			is_mut: is_mut
+			share: table.sharetype_from_flags(is_shared, is_atomic_or_rw)
 			expr: e
 		}
 		if p.tok.kind != .rpar {
@@ -149,7 +151,9 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 	if p.tok.kind == .lpar {
 		p.next() // (
 		is_method = true
-		rec_mut = p.tok.kind == .key_mut
+		is_shared := p.tok.kind in [.key_shared, .key_rwshared]
+		is_atomic_or_rw := p.tok.kind in [.key_rwshared, .key_atomic]
+		rec_mut = p.tok.kind == .key_mut || is_shared || is_atomic_or_rw
 		if rec_mut {
 			p.next() // `mut`
 		}
@@ -172,6 +176,12 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 		if is_amp && rec_mut {
 			p.error('use `(mut f Foo)` or `(f &Foo)` instead of `(mut f &Foo)`')
 		}
+		if is_shared {
+			rec_type = rec_type.set_flag(.shared_f)
+		}
+		if is_atomic_or_rw {
+			rec_type = rec_type.set_flag(.atomic_or_rw)
+		}
 		args << table.Arg{
 			name: rec_name
 			is_mut: rec_mut
@@ -390,7 +400,9 @@ fn (mut p Parser) fn_args() ([]table.Arg, bool, bool) {
 		mut arg_no := 1
 		for p.tok.kind != .rpar {
 			arg_name := 'arg_$arg_no'
-			is_mut := p.tok.kind == .key_mut
+			is_shared := p.tok.kind in [.key_shared, .key_rwshared]
+			is_atomic_or_rw := p.tok.kind in [.key_rwshared, .key_atomic]
+			is_mut := p.tok.kind == .key_mut || is_shared || is_atomic_or_rw
 			if is_mut {
 				p.next()
 			}
@@ -402,13 +414,27 @@ fn (mut p Parser) fn_args() ([]table.Arg, bool, bool) {
 			mut arg_type := p.parse_type()
 			if is_mut {
 				if !arg_type.has_flag(.generic) {
-					p.check_fn_mutable_arguments(arg_type, pos)
+					if is_shared {
+						p.check_fn_shared_arguments(arg_type, pos)
+					} else if is_atomic_or_rw {
+						p.check_fn_atomic_arguments(arg_type, pos)
+					} else {
+						p.check_fn_mutable_arguments(arg_type, pos)
+					}
+				} else if is_shared || is_atomic_or_rw {
+					p.error_with_pos('generic object cannot be `atomic`, `shared` or `rwshared`', pos)
 				}
 				// if arg_type.is_ptr() {
 				// p.error('cannot mut')
 				// }
 				// arg_type = arg_type.to_ptr()
 				arg_type = arg_type.set_nr_muls(1)
+				if is_shared {
+					arg_type = arg_type.set_flag(.shared_f)
+				}
+				if is_atomic_or_rw {
+					arg_type = arg_type.set_flag(.atomic_or_rw)
+				}
 			}
 			if is_variadic {
 				arg_type = arg_type.set_flag(.variadic)
@@ -430,7 +456,9 @@ fn (mut p Parser) fn_args() ([]table.Arg, bool, bool) {
 		}
 	} else {
 		for p.tok.kind != .rpar {
-			mut is_mut := p.tok.kind == .key_mut
+			is_shared := p.tok.kind in [.key_shared, .key_rwshared]
+			is_atomic_or_rw := p.tok.kind in [.key_rwshared, .key_atomic]
+			mut is_mut := p.tok.kind == .key_mut || is_shared || is_atomic_or_rw
 			if is_mut {
 				p.next()
 			}
@@ -455,9 +483,23 @@ fn (mut p Parser) fn_args() ([]table.Arg, bool, bool) {
 			mut typ := p.parse_type()
 			if is_mut {
 				if !typ.has_flag(.generic) {
-					p.check_fn_mutable_arguments(typ, pos)
+					if is_shared {
+						p.check_fn_shared_arguments(typ, pos)
+					} else if is_atomic_or_rw {
+						p.check_fn_atomic_arguments(typ, pos)
+					} else {
+						p.check_fn_mutable_arguments(typ, pos)
+					}
+				} else if is_shared || is_atomic_or_rw {
+					p.error_with_pos('generic object cannot be `atomic`, `shared` or `rwshared`', pos)
 				}
 				typ = typ.set_nr_muls(1)
+				if is_shared {
+					typ = typ.set_flag(.shared_f)
+				}
+				if is_atomic_or_rw {
+					typ = typ.set_flag(.atomic_or_rw)
+				}
 			}
 			if is_variadic {
 				typ = typ.set_flag(.variadic)
@@ -497,6 +539,22 @@ fn (mut p Parser) check_fn_mutable_arguments(typ table.Type, pos token.Position)
 	}
 }
 
+fn (mut p Parser) check_fn_shared_arguments(typ table.Type, pos token.Position) {
+	sym := p.table.get_type_symbol(typ)
+	if sym.kind !in [.array, .struct_, .map, .placeholder] && !typ.is_ptr() {
+		p.error_with_pos('shared arguments are only allowed for arrays, maps, and structs\n', pos)
+	}
+}
+
+fn (mut p Parser) check_fn_atomic_arguments(typ table.Type, pos token.Position) {
+	sym := p.table.get_type_symbol(typ)
+	if sym.kind !in [.u32, .int, .u64] {
+		p.error_with_pos('atomic arguments are only allowed for 32/64 bit integers\n' +
+			'use shared arguments instead: `fn foo(atomic n $sym.name) {` => `fn foo(shared n $sym.name) {`',
+			pos)
+	}
+}
+
 fn (mut p Parser) fn_redefinition_error(name string) {
 	// Find where this function was already declared
 	// TODO
diff --git a/vlib/v/parser/lock.v b/vlib/v/parser/lock.v
new file mode 100644
index 0000000000..c20d32fdfd
--- /dev/null
+++ b/vlib/v/parser/lock.v
@@ -0,0 +1,35 @@
+module parser
+
+import v.ast
+import v.table
+
+fn (mut p Parser) lock_expr() ast.LockExpr {
+	pos := p.tok.position()
+	is_rlock := p.tok.kind == .key_rlock
+	p.next()
+	mut lockeds := []ast.Ident{}
+	for p.tok.kind == .name {
+		lockeds << ast.Ident{
+			language: table.Language.v
+			kind: .variable
+			pos: p.tok.position()
+			name: p.tok.lit
+			is_mut: true
+			info: ast.IdentVar{}
+		}
+		p.next()
+		if p.tok.kind == .lcbr {
+			break
+		}
+		p.check(.comma)
+	}
+	stmts := p.parse_block()
+	return ast.LockExpr {
+		lockeds: lockeds
+		stmts: stmts
+		is_rlock: is_rlock
+		pos: pos
+	}
+}
+
+	
diff --git a/vlib/v/parser/parse_type.v b/vlib/v/parser/parse_type.v
index 3c7f30510b..cee0aaac23 100644
--- a/vlib/v/parser/parse_type.v
+++ b/vlib/v/parser/parse_type.v
@@ -105,8 +105,10 @@ pub fn (mut p Parser) parse_type() table.Type {
 		p.next()
 		is_optional = true
 	}
+	is_shared := p.tok.kind in [.key_shared, .key_rwshared]
+	is_atomic_or_rw := p.tok.kind in [.key_rwshared, .key_atomic]
 	mut nr_muls := 0
-	if p.tok.kind == .key_mut {
+	if p.tok.kind == .key_mut || is_shared || is_atomic_or_rw {
 		nr_muls++
 		p.next()
 	}
@@ -139,6 +141,12 @@ pub fn (mut p Parser) parse_type() table.Type {
 	if is_optional {
 		typ = typ.set_flag(.optional)
 	}
+	if is_shared {
+		typ = typ.set_flag(.shared_f)
+	}
+	if is_atomic_or_rw {
+		typ = typ.set_flag(.atomic_or_rw)
+	}
 	if nr_muls > 0 {
 		typ = typ.set_nr_muls(nr_muls)
 	}
diff --git a/vlib/v/parser/parser.v b/vlib/v/parser/parser.v
index 451fd1ca6f..4abfa5b605 100644
--- a/vlib/v/parser/parser.v
+++ b/vlib/v/parser/parser.v
@@ -506,7 +506,7 @@ pub fn (mut p Parser) stmt(is_top_level bool) ast.Stmt {
 		.key_for {
 			return p.for_stmt()
 		}
-		.name, .key_mut, .key_static, .mul {
+		.name, .key_mut, .key_shared, .key_atomic, .key_rwshared, .key_static, .mul {
 			if p.tok.kind == .name {
 				if p.tok.lit == 'sql' {
 					return p.sql_stmt()
@@ -750,7 +750,7 @@ fn (mut p Parser) parse_multi_expr(is_top_level bool) ast.Stmt {
 	left0 := left[0]
 	if p.tok.kind in [.assign, .decl_assign] || p.tok.kind.is_assign() {
 		return p.partial_assign_stmt(left)
-	} else if is_top_level && tok.kind !in [.key_if, .key_match] &&
+	} else if is_top_level && tok.kind !in [.key_if, .key_match, .key_lock, .key_rlock] &&
 		left0 !is ast.CallExpr && left0 !is ast.PostfixExpr && !(left0 is ast.InfixExpr &&
 		(left0 as ast.InfixExpr).op == .left_shift) &&
 		left0 !is ast.ComptimeCall {
@@ -773,7 +773,9 @@ fn (mut p Parser) parse_multi_expr(is_top_level bool) ast.Stmt {
 
 pub fn (mut p Parser) parse_ident(language table.Language) ast.Ident {
 	// p.warn('name ')
-	is_mut := p.tok.kind == .key_mut
+	is_shared := p.tok.kind in [.key_shared, .key_rwshared]
+	is_atomic_or_rw := p.tok.kind in [.key_rwshared, .key_atomic]
+	is_mut := p.tok.kind == .key_mut || is_shared || is_atomic_or_rw
 	if is_mut {
 		p.next()
 	}
@@ -811,6 +813,7 @@ pub fn (mut p Parser) parse_ident(language table.Language) ast.Ident {
 			info: ast.IdentVar{
 				is_mut: is_mut
 				is_static: is_static
+				share: table.sharetype_from_flags(is_shared, is_atomic_or_rw)
 			}
 		}
 	} else {
diff --git a/vlib/v/parser/pratt.v b/vlib/v/parser/pratt.v
index a594282e5a..0f8808e381 100644
--- a/vlib/v/parser/pratt.v
+++ b/vlib/v/parser/pratt.v
@@ -16,7 +16,7 @@ pub fn (mut p Parser) expr(precedence int) ast.Expr {
 	p.eat_comments()
 	// Prefix
 	match p.tok.kind {
-		.key_mut, .key_static {
+		.key_mut, .key_shared, .key_rwshared, .key_atomic, .key_static {
 			node = p.name_expr()
 			p.is_stmt_ident = is_stmt_ident
 		}
@@ -79,6 +79,9 @@ pub fn (mut p Parser) expr(precedence int) ast.Expr {
 		.key_if {
 			node = p.if_expr()
 		}
+		.key_lock, .key_rlock {
+			node = p.lock_expr()
+		}
 		.lsbr {
 			if p.expecting_type {
 				// parse json.decode type (`json.decode([]User, s)`)
diff --git a/vlib/v/table/atypes.v b/vlib/v/table/atypes.v
index 993afdc897..c186db3c53 100644
--- a/vlib/v/table/atypes.v
+++ b/vlib/v/table/atypes.v
@@ -41,6 +41,49 @@ pub enum TypeFlag {
 	optional
 	variadic
 	generic
+	shared_f
+	atomic_or_rw
+}
+
+/* 
+	To save precious TypeFlag bits the 4 possible ShareTypes are coded in the two
+	bits `shared` and `atomic_or_rw` (see sharetype_from_flags() below).
+*/
+
+pub enum ShareType {
+	mut_t
+	shared_t
+	atomic_t
+	rwshared_t
+}
+
+pub fn (t ShareType) str() string {
+	match t {
+		.mut_t { return 'mut' }
+		.shared_t { return 'shared' }
+		.atomic_t { return 'atomic' }
+		.rwshared_t { return 'rwshared' }
+	}
+}
+
+// <atomic.h> defines special typenames
+pub fn (t Type) atomic_typename() string {
+	idx := t.idx()
+	match idx {
+		u32_type_idx { return 'atomic_uint' }
+		int_type_idx { return 'atomic_int' }
+		u64_type_idx { return 'atomic_ullong' }
+		i64_type_idx { return 'atomic_llong' }
+		else { return 'unknown_atomic' }
+	}
+}
+
+pub fn sharetype_from_flags(is_shared, is_atomic_or_rw bool) ShareType {
+	return ShareType((int(is_atomic_or_rw) << 1) | int(is_shared))
+}
+
+pub fn (t Type) share() ShareType {
+	return sharetype_from_flags(t.has_flag(.shared_f), t.has_flag(.atomic_or_rw))
 }
 
 pub fn (types []Type) contains(typ Type) bool {
diff --git a/vlib/v/tests/shared_lock_2_test.v b/vlib/v/tests/shared_lock_2_test.v
new file mode 100644
index 0000000000..9283968731
--- /dev/null
+++ b/vlib/v/tests/shared_lock_2_test.v
@@ -0,0 +1,53 @@
+import sync
+import time
+
+struct St {
+mut:
+	a int
+}
+
+fn (shared x St) f(shared y St, shared z St) {
+	for _ in 0..101 {
+		lock x, y {
+			tmp := y.a
+			y.a = x.a
+			x.a = tmp
+		}
+	}
+	lock z {
+		z.a--
+	}
+}
+
+fn test_shared_receiver_lock() {
+	shared x := &St{
+		a: 5
+	}
+	shared y := &St{
+		a: 7
+	}
+	shared z := &St{
+		a: 1
+	}
+	go x.f(shared y, shared z)
+	for _ in 0..100 {
+		lock x, y {
+			tmp := x.a
+			x.a = y.a
+			y.a = tmp
+		}
+	}
+	// the following would be a good application for a channel
+	for finished := false; ; {
+		lock z {
+			finished = z.a == 0
+		}
+		if finished {
+			break
+		}
+		time.sleep_ms(100)
+	}
+	lock x, y {
+		assert x.a == 7 && y.a == 5
+	}
+}
diff --git a/vlib/v/tests/shared_lock_test.v b/vlib/v/tests/shared_lock_test.v
new file mode 100644
index 0000000000..9fc2a35531
--- /dev/null
+++ b/vlib/v/tests/shared_lock_test.v
@@ -0,0 +1,53 @@
+import sync
+import time
+
+struct St {
+mut:
+	a int
+}
+
+fn f(shared x St, shared y St, shared z St) {
+	for _ in 0..101 {
+		lock x, y {
+			tmp := y.a
+			y.a = x.a
+			x.a = tmp
+		}
+	}
+	lock z {
+		z.a--
+	}
+}
+
+fn test_shared_lock() {
+	shared x := &St{
+		a: 5
+	}
+	shared y := &St{
+		a: 7
+	}
+	shared z := &St{
+		a: 1
+	}
+	go f(shared x, shared y, shared z)
+	for _ in 0..100 {
+		lock x, y {
+			tmp := x.a
+			x.a = y.a
+			y.a = tmp
+		}
+	}
+	// the following would be a good application for a channel
+	for finished := false; ; {
+		lock z {
+			finished = z.a == 0
+		}
+		if finished {
+			break
+		}
+		time.sleep_ms(100)
+	}
+	lock x, y {
+		assert x.a == 7 && y.a == 5
+	}
+}
diff --git a/vlib/v/token/token.v b/vlib/v/token/token.v
index ff7a57906c..54324d6f0a 100644
--- a/vlib/v/token/token.v
+++ b/vlib/v/token/token.v
@@ -108,6 +108,10 @@ pub enum Kind {
 	key_match
 	key_module
 	key_mut
+	key_shared
+	key_rwshared
+	key_lock
+	key_rlock
 	key_none
 	key_return
 	key_select
@@ -226,6 +230,10 @@ fn build_token_str() []string {
 	s[Kind.key_goto] = 'goto'
 	s[Kind.key_const] = 'const'
 	s[Kind.key_mut] = 'mut'
+	s[Kind.key_shared] = 'shared'
+	s[Kind.key_rwshared] = 'rwshared'
+	s[Kind.key_lock] = 'lock'
+	s[Kind.key_rlock] = 'rlock'
 	s[Kind.key_type] = 'type'
 	s[Kind.key_for] = 'for'
 	s[Kind.key_switch] = 'switch'