runtime: stack allocator, separate from mallocgc

In order to move malloc to Go, we need to have a
separate stack allocator.  If we run out of stack
during malloc, malloc will not be available
to allocate a new stack.

Stacks are the last remaining FlagNoGC objects in the
GC heap.  Once they are out, we can get rid of the
distinction between the allocated/blockboundary bits.
(This will be in a separate change.)

Fixes #7468
Fixes #7424

LGTM=rsc, dvyukov
R=golang-codereviews, dvyukov, khr, dave, rsc
CC=golang-codereviews
https://golang.org/cl/104200047

1 files changed, 2 insertions, 1 deletions

diff --git a/src/pkg/runtime/proc.c b/src/pkg/runtime/proc.c
index 04808f2c50..ccaddee2eb 100644
--- a/src/pkg/runtime/proc.c
+++ b/src/pkg/runtime/proc.c
@@ -152,6 +152,7 @@ runtime·schedinit(void)
 	runtime·precisestack = true; // haveexperiment("precisestack");
 
 	runtime·symtabinit();
+	runtime·stackinit();
 	runtime·mallocinit();
 	mcommoninit(g->m);
 	
@@ -1926,7 +1927,7 @@ gfput(P *p, G *gp)
 		runtime·throw("gfput: bad stacksize");
 	}
 	top = (Stktop*)gp->stackbase;
-	if(top->malloced) {
+	if(stksize != FixedStack) {
 		// non-standard stack size - free it.
 		runtime·stackfree(gp, (void*)gp->stack0, top);
 		gp->stack0 = 0;