From e7384a38af94ff5e7e748f1424d766e1d3316f8d Mon Sep 17 00:00:00 2001
From: Jason A. Donenfeld <Jason@zx2c4.com>
Date: Tue, 27 Aug 2019 06:46:16 -0600
Subject: [PATCH] runtime: monitor for suspend/resume to kick timeouts

Starting in Windows 8, the wait functions don't take into account
suspend time, even though the monotonic counters do. This results in
timer buckets stalling on resume. Therefore, this commit makes it so
that on resume, we return from the wait functions and recalculate the
amount of time left to wait.

Fixes: #31528

Change-Id: I0db02cc72188cb620954e87a0180e0a3c83f4a56
---

diff --git a/src/runtime/os_windows.go b/src/runtime/os_windows.go
index 074ae0f..6cc9670 100644
--- a/src/runtime/os_windows.go
+++ b/src/runtime/os_windows.go
@@ -49,6 +49,7 @@
 //go:cgo_import_dynamic runtime._VirtualFree VirtualFree%3 "kernel32.dll"
 //go:cgo_import_dynamic runtime._VirtualQuery VirtualQuery%3 "kernel32.dll"
 //go:cgo_import_dynamic runtime._WaitForSingleObject WaitForSingleObject%2 "kernel32.dll"
+//go:cgo_import_dynamic runtime._WaitForMultipleObjects WaitForMultipleObjects%4 "kernel32.dll"
 //go:cgo_import_dynamic runtime._WriteConsoleW WriteConsoleW%5 "kernel32.dll"
 //go:cgo_import_dynamic runtime._WriteFile WriteFile%5 "kernel32.dll"
 
@@ -96,6 +97,7 @@
 	_VirtualFree,
 	_VirtualQuery,
 	_WaitForSingleObject,
+	_WaitForMultipleObjects,
 	_WriteConsoleW,
 	_WriteFile,
 	_ stdFunction
@@ -139,7 +141,8 @@
 func ctrlhandler()
 
 type mOS struct {
-	waitsema uintptr // semaphore for parking on locks
+	waitsema   uintptr // semaphore for parking on locks
+	resumesema uintptr // semaphore to indicate suspend/resume
 }
 
 //go:linkname os_sigpipe os.sigpipe
@@ -258,6 +261,34 @@
 	}
 }
 
+func monitorSuspendResume() {
+	powrprof := windowsLoadSystemLib([]byte("powrprof.dll\000"))
+	if powrprof == 0 {
+		return // Running on Windows 7, where we don't need it anyway.
+	}
+	powerRegisterSuspendResumeNotification := windowsFindfunc(powrprof, []byte("PowerRegisterSuspendResumeNotification\000"))
+	if powerRegisterSuspendResumeNotification == nil {
+		return // Running on Windows 7, where we don't need it anyway.
+	}
+	var fn interface{} = func(context uintptr, changeType uint32, setting uintptr) uintptr {
+		lock(&allglock)
+		for _, gp := range allgs {
+			if gp.m != nil && gp.m.resumesema != 0 {
+				stdcall1(_SetEvent, gp.m.resumesema)
+			}
+		}
+		unlock(&allglock)
+		return 0
+	}
+	var handle uintptr
+	callback := compileCallback(*efaceOf(&fn), true)
+	if stdcall3(powerRegisterSuspendResumeNotification, 2,
+		uintptr(unsafe.Pointer(&[2]uintptr{callback, 0})),
+		uintptr(unsafe.Pointer(&handle))) != 0 {
+		throw("PowerRegisterSuspendResumeNotification failure")
+	}
+}
+
 //go:nosplit
 func getLoadLibrary() uintptr {
 	return uintptr(unsafe.Pointer(_LoadLibraryW))
@@ -488,6 +519,10 @@
 	}
 
 	stdcall1(_FreeEnvironmentStringsW, uintptr(strings))
+
+	// We call this all the way here, late in init, so that malloc works
+	// for the callback function this generates.
+	monitorSuspendResume()
 }
 
 // exiting is set to non-zero when the process is exiting.
@@ -606,21 +641,34 @@
 		_WAIT_FAILED    = 0xFFFFFFFF
 	)
 
-	// store ms in ns to save stack space
+	var result uintptr
+	var elapsed, start int64
+retry:
 	if ns < 0 {
-		ns = _INFINITE
+		result = stdcall2(_WaitForSingleObject, getg().m.waitsema, uintptr(_INFINITE))
 	} else {
-		ns = int64(timediv(ns, 1000000, nil))
-		if ns == 0 {
-			ns = 1
+		if start == 0 {
+			start = nanotime()
 		}
+		ms := int64(timediv(ns-elapsed, 1000000, nil))
+		if ms == 0 {
+			ms = 1
+		}
+		result = stdcall4(_WaitForMultipleObjects, 2,
+			uintptr(unsafe.Pointer(&[2]uintptr{getg().m.waitsema, getg().m.resumesema})),
+			0, uintptr(ms))
 	}
-
-	result := stdcall2(_WaitForSingleObject, getg().m.waitsema, uintptr(ns))
 	switch result {
 	case _WAIT_OBJECT_0: //signaled
 		return 0
 
+	case _WAIT_OBJECT_0 + 1: //system resume
+		elapsed = nanotime() - start
+		if elapsed >= ns {
+			return -1
+		}
+		goto retry
+
 	case _WAIT_TIMEOUT:
 		return -1
 
@@ -667,6 +715,15 @@
 			throw("runtime.semacreate")
 		})
 	}
+	mp.resumesema = stdcall4(_CreateEventA, 0, 0, 0, 0)
+	if mp.resumesema == 0 {
+		systemstack(func() {
+			print("runtime: createevent failed; errno=", getlasterror(), "\n")
+			throw("runtime.semacreate")
+		})
+		stdcall1(_CloseHandle, mp.waitsema)
+		mp.waitsema = 0
+	}
 }
 
 // May run with m.p==nil, so write barriers are not allowed. This
diff --git a/src/runtime/syscall_windows.go b/src/runtime/syscall_windows.go
index 722a73d..0e2fcfb 100644
--- a/src/runtime/syscall_windows.go
+++ b/src/runtime/syscall_windows.go
@@ -74,16 +74,18 @@
 		argsize += uintptrSize
 	}
 
-	lock(&cbs.lock)
-	defer unlock(&cbs.lock)
+	lock(&cbs.lock) // We don't unlock this in a defer because this is used from the system stack.
 
 	n := cbs.n
 	for i := 0; i < n; i++ {
 		if cbs.ctxt[i].gobody == fn.data && cbs.ctxt[i].isCleanstack() == cleanstack {
-			return callbackasmAddr(i)
+			r := callbackasmAddr(i)
+			unlock(&cbs.lock)
+			return r
 		}
 	}
 	if n >= cb_max {
+		unlock(&cbs.lock)
 		throw("too many callback functions")
 	}
 
@@ -99,7 +101,9 @@
 	cbs.ctxt[n] = c
 	cbs.n++
 
-	return callbackasmAddr(n)
+	r := callbackasmAddr(n)
+	unlock(&cbs.lock)
+	return r
 }
 
 const _LOAD_LIBRARY_SEARCH_SYSTEM32 = 0x00000800