runtime: free Windows event handles after last lock is dropped

Calls to lock may need to use global members of mOS that also need to be
cleaned up before the thread exits. Before this commit, these resources
would leak. Moving them to be cleaned up in unminit, however, would race
with gstack on unix. So this creates a new helper, mdestroy, to release
resources that must be destroyed only after locks are no longer
required. We also move highResTimer lifetime to the same semantics,
since it doesn't help to constantly acquire and release the timer object
during dropm.

Updates #43720.

Change-Id: Ib3f598f3fda1b2bbcb608099616fa4f85bc1c289
Reviewed-on: https://go-review.googlesource.com/c/go/+/284137
Run-TryBot: Jason A. Donenfeld <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Reviewed-by: Austin Clements <[email protected]>
Trust: Alex Brainman <[email protected]>
Trust: Jason A. Donenfeld <[email protected]>

Author: zx2c4

src/runtime/os3_solaris.go

@@ -227,6 +227,11 @@ func unminit() {
 	unminitSignals()
 }
 
+// Called from exitm, but not from drop, to undo the effect of thread-owned
+// resources in minit, semacreate, or elsewhere. Do not take locks after calling this.
+func mdestroy(mp *m) {
+}
+
 func sigtramp()
 
 //go:nosplit

src/runtime/os_aix.go

@@ -180,6 +180,11 @@ func unminit() {
 	unminitSignals()
 }
 
+// Called from exitm, but not from drop, to undo the effect of thread-owned
+// resources in minit, semacreate, or elsewhere. Do not take locks after calling this.
+func mdestroy(mp *m) {
+}
+
 // tstart is a function descriptor to _tstart defined in assembly.
 var tstart funcDescriptor
 

src/runtime/os_darwin.go

@@ -325,6 +325,11 @@ func unminit() {
 	}
 }
 
+// Called from exitm, but not from drop, to undo the effect of thread-owned
+// resources in minit, semacreate, or elsewhere. Do not take locks after calling this.
+func mdestroy(mp *m) {
+}
+
 //go:nosplit
 func osyield() {
 	usleep(1)

src/runtime/os_dragonfly.go

@@ -203,6 +203,11 @@ func unminit() {
 	unminitSignals()
 }
 
+// Called from exitm, but not from drop, to undo the effect of thread-owned
+// resources in minit, semacreate, or elsewhere. Do not take locks after calling this.
+func mdestroy(mp *m) {
+}
+
 func sigtramp()
 
 type sigactiont struct {

src/runtime/os_freebsd.go

@@ -319,6 +319,11 @@ func unminit() {
 	unminitSignals()
 }
 
+// Called from exitm, but not from drop, to undo the effect of thread-owned
+// resources in minit, semacreate, or elsewhere. Do not take locks after calling this.
+func mdestroy(mp *m) {
+}
+
 func sigtramp()
 
 type sigactiont struct {

src/runtime/os_js.go

@@ -84,6 +84,11 @@ func minit() {
 func unminit() {
 }
 
+// Called from exitm, but not from drop, to undo the effect of thread-owned
+// resources in minit, semacreate, or elsewhere. Do not take locks after calling this.
+func mdestroy(mp *m) {
+}
+
 func osinit() {
 	ncpu = 1
 	getg().m.procid = 2

src/runtime/os_linux.go

@@ -375,6 +375,11 @@ func unminit() {
 	unminitSignals()
 }
 
+// Called from exitm, but not from drop, to undo the effect of thread-owned
+// resources in minit, semacreate, or elsewhere. Do not take locks after calling this.
+func mdestroy(mp *m) {
+}
+
 //#ifdef GOARCH_386
 //#define sa_handler k_sa_handler
 //#endif

src/runtime/os_netbsd.go

@@ -290,6 +290,11 @@ func unminit() {
 	unminitSignals()
 }
 
+// Called from exitm, but not from drop, to undo the effect of thread-owned
+// resources in minit, semacreate, or elsewhere. Do not take locks after calling this.
+func mdestroy(mp *m) {
+}
+
 func sigtramp()
 
 type sigactiont struct {

src/runtime/os_openbsd.go

@@ -257,6 +257,11 @@ func unminit() {
 	unminitSignals()
 }
 
+// Called from exitm, but not from drop, to undo the effect of thread-owned
+// resources in minit, semacreate, or elsewhere. Do not take locks after calling this.
+func mdestroy(mp *m) {
+}
+
 func sigtramp()
 
 type sigactiont struct {

src/runtime/os_plan9.go

@@ -213,6 +213,11 @@ func minit() {
 func unminit() {
 }
 
+// Called from exitm, but not from drop, to undo the effect of thread-owned
+// resources in minit, semacreate, or elsewhere. Do not take locks after calling this.
+func mdestroy(mp *m) {
+}
+
 var sysstat = []byte("/dev/sysstat\x00")
 
 func getproccount() int32 {

src/runtime/os_windows.go

@@ -898,20 +898,18 @@ func minit() {
 		throw("runtime.minit: duplicatehandle failed")
 	}
 
+	mp := getg().m
+	lock(&mp.threadLock)
+	mp.thread = thandle
+
 	// Configure usleep timer, if possible.
-	var timer uintptr
-	if haveHighResTimer {
-		timer = createHighResTimer()
-		if timer == 0 {
+	if mp.highResTimer == 0 && haveHighResTimer {
+		mp.highResTimer = createHighResTimer()
+		if mp.highResTimer == 0 {
 			print("runtime: CreateWaitableTimerEx failed; errno=", getlasterror(), "\n")
 			throw("CreateWaitableTimerEx when creating timer failed")
 		}
 	}
-
-	mp := getg().m
-	lock(&mp.threadLock)
-	mp.thread = thandle
-	mp.highResTimer = timer
 	unlock(&mp.threadLock)
 
 	// Query the true stack base from the OS. Currently we're
@@ -947,13 +945,29 @@ func minit() {
 func unminit() {
 	mp := getg().m
 	lock(&mp.threadLock)
-	stdcall1(_CloseHandle, mp.thread)
-	mp.thread = 0
+	if mp.thread != 0 {
+		stdcall1(_CloseHandle, mp.thread)
+		mp.thread = 0
+	}
+	unlock(&mp.threadLock)
+}
+
+// Called from exitm, but not from drop, to undo the effect of thread-owned
+// resources in minit, semacreate, or elsewhere. Do not take locks after calling this.
+//go:nosplit
+func mdestroy(mp *m) {
 	if mp.highResTimer != 0 {
 		stdcall1(_CloseHandle, mp.highResTimer)
 		mp.highResTimer = 0
 	}
-	unlock(&mp.threadLock)
+	if mp.waitsema != 0 {
+		stdcall1(_CloseHandle, mp.waitsema)
+		mp.waitsema = 0
+	}
+	if mp.resumesema != 0 {
+		stdcall1(_CloseHandle, mp.resumesema)
+		mp.resumesema = 0
+	}
 }
 
 // Calling stdcall on os stack.

src/runtime/proc.go

@@ -1407,6 +1407,10 @@ found:
 		}
 	}
 
+	// Destroy all allocated resources. After this is called, we may no
+	// longer take any locks.
+	mdestroy(m)
+
 	if osStack {
 		// Return from mstart and let the system thread
 		// library free the g0 stack and terminate the thread.