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

1 files changed, 9 insertions, 2 deletions

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));
 }