9 files changed, 68 insertions, 12 deletions
diff --git a/src/pkg/runtime/proc.c b/src/pkg/runtime/proc.c
index 67d6dad488..5c36ddf745 100644
--- a/src/pkg/runtime/proc.c
+++ b/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;
diff --git a/src/pkg/runtime/runtime.h b/src/pkg/runtime/runtime.h
index 8162874bbe..4ca7cc7dc9 100644
--- a/src/pkg/runtime/runtime.h
+++ b/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);
diff --git a/src/pkg/runtime/thread_darwin.c b/src/pkg/runtime/thread_darwin.c
index 1d6037b48b..1a13eba1cd 100644
--- a/src/pkg/runtime/thread_darwin.c
+++ b/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);
diff --git a/src/pkg/runtime/thread_freebsd.c b/src/pkg/runtime/thread_freebsd.c
index 4d5f69a9f3..d7758eaafb 100644
--- a/src/pkg/runtime/thread_freebsd.c
+++ b/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);
 }
diff --git a/src/pkg/runtime/thread_linux.c b/src/pkg/runtime/thread_linux.c
index 02a5eaee2f..85c3e6b8cf 100644
--- a/src/pkg/runtime/thread_linux.c
+++ b/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));
 }
diff --git a/src/pkg/runtime/thread_netbsd.c b/src/pkg/runtime/thread_netbsd.c
index ebef45e757..aba8fea7a2 100644
--- a/src/pkg/runtime/thread_netbsd.c
+++ b/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);
 }
diff --git a/src/pkg/runtime/thread_openbsd.c b/src/pkg/runtime/thread_openbsd.c
index 8433e8bae5..525dc697e0 100644
--- a/src/pkg/runtime/thread_openbsd.c
+++ b/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);
 }
diff --git a/src/pkg/runtime/thread_plan9.c b/src/pkg/runtime/thread_plan9.c
index bca0deac62..625c8b48d4 100644
--- a/src/pkg/runtime/thread_plan9.c
+++ b/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();
diff --git a/src/pkg/runtime/thread_windows.c b/src/pkg/runtime/thread_windows.c
index 7110c6efe4..4d95e99870 100644
--- a/src/pkg/runtime/thread_windows.c
+++ b/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)
 {