runtime: disable preemption in several scheduler functions

Required for preemptive scheduler, see the comments for details.

R=golang-dev, khr, iant, khr
CC=golang-dev
https://golang.org/cl/9740051

diff --git a/src/pkg/runtime/proc.c b/src/pkg/runtime/proc.c
index 5b5d9b8a0b066ebeae853f3803b66448dd421668..c27d1f5f55a7b5fc25945181841154cae781ded3 100644 (file)
--- a/src/pkg/runtime/proc.c
+++ b/src/pkg/runtime/proc.c
@@ -274,6 +274,7 @@ void
 runtime·ready(G *gp)
 {
        // Mark runnable.
+       m->locks++;  // disable preemption because it can be holding p in a local var
        if(gp->status != Gwaiting) {
                runtime·printf("goroutine %D has status %d\n", gp->goid, gp->status);
                runtime·throw("bad g->status in ready");
@@ -282,6 +283,7 @@ runtime·ready(G *gp)
        runqput(m->p, gp);
        if(runtime·atomicload(&runtime·sched.npidle) != 0 && runtime·atomicload(&runtime·sched.nmspinning) == 0)  // TODO: fast atomic
                wakep();
+       m->locks--;
 }
 
 int32
@@ -398,6 +400,7 @@ runtime·starttheworld(void)
        G *gp;
        bool add;
 
+       m->locks++;  // disable preemption because it can be holding p in a local var
        gp = runtime·netpoll(false);  // non-blocking
        injectglist(gp);
        add = needaddgcproc();
@@ -451,6 +454,7 @@ runtime·starttheworld(void)
                // the maximum number of procs.
                newm(mhelpgc, nil);
        }
+       m->locks--;
 }
 
 // Called to start an M.
@@ -1509,6 +1513,7 @@ runtime·newproc1(FuncVal *fn, byte *argp, int32 narg, int32 nret, void *callerp
        int32 siz;
 
 //runtime·printf("newproc1 %p %p narg=%d nret=%d\n", fn->fn, argp, narg, nret);
+       m->locks++;  // disable preemption because it can be holding p in a local var
        siz = narg + nret;
        siz = (siz+7) & ~7;
 
@@ -1555,6 +1560,7 @@ runtime·newproc1(FuncVal *fn, byte *argp, int32 narg, int32 nret, void *callerp
 
        if(runtime·atomicload(&runtime·sched.npidle) != 0 && runtime·atomicload(&runtime·sched.nmspinning) == 0 && fn->fn != runtime·main)  // TODO: fast atomic
                wakep();
+       m->locks--;
        return newg;
 }