cmd/gc: racewalk: collect stack traces in sync and sync/atomic

W/o this change stack traces do not show from where sync.Once()
or atomic.XXX was called.
This change add funcenter/exit instrumentation to sync/sync.atomic
packages.

R=golang-dev
CC=golang-dev
https://golang.org/cl/6854112

diff --git a/src/cmd/gc/racewalk.c b/src/cmd/gc/racewalk.c
index 17e02a19b2b8fbe655a2b0ee184197e62f7837e5..2d216ec67aa5fc403431333c84d029dbdd69706f 100644 (file)
--- a/src/cmd/gc/racewalk.c
+++ b/src/cmd/gc/racewalk.c
@@ -28,26 +28,42 @@ static void foreach(Node *n, void(*f)(Node*, void*), void *c);
 static void hascallspred(Node *n, void *c);
 static Node* detachexpr(Node *n, NodeList **init);
 
-static const char *omitPkgs[] = {"runtime", "runtime/race", "sync", "sync/atomic"};
+// Do not instrument the following packages at all,
+// at best instrumentation would cause infinite recursion.
+static const char *omit_pkgs[] = {"runtime", "runtime/race"};
+// Only insert racefuncenter/racefuncexit into the following packages.
+// Memory accesses in the packages are either uninteresting or will cause false positives.
+static const char *noinst_pkgs[] = {"sync", "sync/atomic"};
+
+static int
+ispkgin(const char **pkgs, int n)
+{
+       int i;
+
+       if(myimportpath) {
+               for(i=0; i<n; i++) {
+                       if(strcmp(myimportpath, pkgs[i]) == 0)
+                               return 1;
+               }
+       }
+       return 0;
+}
 
 void
 racewalk(Node *fn)
 {
-       int i;
        Node *nd;
        Node *nodpc;
        char s[1024];
 
-       if(myimportpath) {
-               for(i=0; i<nelem(omitPkgs); i++) {
-                       if(strcmp(myimportpath, omitPkgs[i]) == 0)
-                               return;
-               }
-       }
+       if(ispkgin(omit_pkgs, nelem(omit_pkgs)))
+               return;
 
-       racewalklist(fn->nbody, nil);
-       // nothing interesting for race detector in fn->enter
-       racewalklist(fn->exit, nil);
+       if(!ispkgin(noinst_pkgs, nelem(noinst_pkgs))) {
+               racewalklist(fn->nbody, nil);
+               // nothing interesting for race detector in fn->enter
+               racewalklist(fn->exit, nil);
+       }
 
        // nodpc is the PC of the caller as extracted by
        // getcallerpc. We use -widthptr(FP) for x86.