runtime: split minit() to mpreinit() and minit()

mpreinit() is called on the parent thread and with mcache (can allocate memory),
minit() is called on the child thread and can not allocate memory.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/7389043

src/pkg/runtime/proc.c

@@ -370,6 +370,8 @@ mcommoninit(M *mp)
 
 	runtime·callers(1, mp->createstack, nelem(mp->createstack));
 
+	runtime·mpreinit(mp);
+
 	// Add to runtime·allm so garbage collector doesn't free m
 	// when it is just in a register or thread-local storage.
 	mp->alllink = runtime·allm;

src/pkg/runtime/runtime.h

@@ -660,6 +660,7 @@ int32	runtime·atoi(byte*);
 void	runtime·newosproc(M *mp, G *gp, void *stk, void (*fn)(void));
 G*	runtime·malg(int32);
 void	runtime·asminit(void);
+void	runtime·mpreinit(M*);
 void	runtime·minit(void);
 void	runtime·unminit(void);
 void	runtime·signalstack(byte*, int32);

src/pkg/runtime/thread_darwin.c

@@ -109,12 +109,19 @@ runtime·newosproc(M *mp, G *gp, void *stk, void (*fn)(void))
 }
 
 // Called to initialize a new m (including the bootstrap m).
+// Called on the parent thread (main thread in case of bootstrap), can allocate memory.
+void
+runtime·mpreinit(M *mp)
+{
+	mp->gsignal = runtime·malg(32*1024);	// OS X wants >=8K, Linux >=2K
+}
+
+// Called to initialize a new m (including the bootstrap m).
+// Called on the new thread, can not allocate memory.
 void
 runtime·minit(void)
 {
 	// Initialize signal handling.
-	if(m->gsignal == nil)
-		m->gsignal = runtime·malg(32*1024);	// OS X wants >=8K, Linux >=2K
 	runtime·signalstack((byte*)m->gsignal->stackguard - StackGuard, 32*1024);
 
 	runtime·sigprocmask(SIG_SETMASK, &sigset_none, nil);

src/pkg/runtime/thread_freebsd.c

@@ -121,11 +121,19 @@ runtime·goenvs(void)
 }
 
 // Called to initialize a new m (including the bootstrap m).
+// Called on the parent thread (main thread in case of bootstrap), can allocate memory.
+void
+runtime·mpreinit(M *mp)
+{
+	mp->gsignal = runtime·malg(32*1024);
+}
+
+// Called to initialize a new m (including the bootstrap m).
+// Called on the new thread, can not allocate memory.
 void
 runtime·minit(void)
 {
 	// Initialize signal handling
-	m->gsignal = runtime·malg(32*1024);
 	runtime·signalstack((byte*)m->gsignal->stackguard - StackGuard, 32*1024);
 	runtime·sigprocmask(&sigset_none, nil);
 }

src/pkg/runtime/thread_linux.c

@@ -171,12 +171,19 @@ runtime·goenvs(void)
 }
 
 // Called to initialize a new m (including the bootstrap m).
+// Called on the parent thread (main thread in case of bootstrap), can allocate memory.
+void
+runtime·mpreinit(M *mp)
+{
+	mp->gsignal = runtime·malg(32*1024);	// OS X wants >=8K, Linux >=2K
+}
+
+// Called to initialize a new m (including the bootstrap m).
+// Called on the new thread, can not allocate memory.
 void
 runtime·minit(void)
 {
 	// Initialize signal handling.
-	if(m->gsignal == nil)
-		m->gsignal = runtime·malg(32*1024);	// OS X wants >=8K, Linux >=2K
 	runtime·signalstack((byte*)m->gsignal->stackguard - StackGuard, 32*1024);
 	runtime·rtsigprocmask(SIG_SETMASK, &sigset_none, nil, sizeof(Sigset));
 }

src/pkg/runtime/thread_netbsd.c

@@ -187,14 +187,21 @@ runtime·goenvs(void)
 }
 
 // Called to initialize a new m (including the bootstrap m).
+// Called on the parent thread (main thread in case of bootstrap), can allocate memory.
+void
+runtime·mpreinit(M *mp)
+{
+	mp->gsignal = runtime·malg(32*1024);
+}
+
+// Called to initialize a new m (including the bootstrap m).
+// Called on the new thread, can not allocate memory.
 void
 runtime·minit(void)
 {
 	m->procid = runtime·lwp_self();
 
 	// Initialize signal handling
-	if(m->gsignal == nil)
-		m->gsignal = runtime·malg(32*1024);
 	runtime·signalstack((byte*)m->gsignal->stackguard - StackGuard, 32*1024);
 	runtime·sigprocmask(SIG_SETMASK, &sigset_none, nil);
 }

src/pkg/runtime/thread_openbsd.c

@@ -166,12 +166,19 @@ runtime·goenvs(void)
 }
 
 // Called to initialize a new m (including the bootstrap m).
+// Called on the parent thread (main thread in case of bootstrap), can allocate memory.
+void
+runtime·mpreinit(M *mp)
+{
+	mp->gsignal = runtime·malg(32*1024);
+}
+
+// Called to initialize a new m (including the bootstrap m).
+// Called on the new thread, can not allocate memory.
 void
 runtime·minit(void)
 {
 	// Initialize signal handling
-	if(m->gsignal == nil)
-		m->gsignal = runtime·malg(32*1024);
 	runtime·signalstack((byte*)m->gsignal->stackguard - StackGuard, 32*1024);
 	runtime·sigprocmask(SIG_SETMASK, sigset_none);
 }

src/pkg/runtime/thread_plan9.c

@@ -11,13 +11,21 @@ extern SigTab runtime·sigtab[];
 
 int32 runtime·postnote(int32, int8*);
 
+// Called to initialize a new m (including the bootstrap m).
+// Called on the parent thread (main thread in case of bootstrap), can allocate memory.
 void
-runtime·minit(void)
+runtime·mpreinit(M *mp)
 {
 	// Initialize stack and goroutine for note handling.
-	m->gsignal = runtime·malg(32*1024);
-	m->notesig = (int8*)runtime·malloc(ERRMAX*sizeof(int8));
+	mp->gsignal = runtime·malg(32*1024);
+	mp->notesig = (int8*)runtime·malloc(ERRMAX*sizeof(int8));
+}
 
+// Called to initialize a new m (including the bootstrap m).
+// Called on the new thread, can not allocate memory.
+void
+runtime·minit(void)
+{
 	// Mask all SSE floating-point exceptions
 	// when running on the 64-bit kernel.
 	runtime·setfpmasks();

src/pkg/runtime/thread_windows.c

@@ -206,6 +206,15 @@ runtime·newosproc(M *mp, G *gp, void *stk, void (*fn)(void))
 }
 
 // Called to initialize a new m (including the bootstrap m).
+// Called on the parent thread (main thread in case of bootstrap), can allocate memory.
+void
+runtime·mpreinit(M *mp)
+{
+	USED(mp);
+}
+
+// Called to initialize a new m (including the bootstrap m).
+// Called on the new thread, can not allocate memory.
 void
 runtime·minit(void)
 {