runtime: make pprof a little nicer

Update #8942

This does not fully address issue 8942 but it does make
the profiles much more useful, until that issue can be
fixed completely.

LGTM=dvyukov
R=r, dvyukov
CC=golang-codereviews
https://golang.org/cl/159990043

diff --git a/src/runtime/proc.c b/src/runtime/proc.c
index 1426790f407c264ce914bc920eeeb8bad3132a93..332121e9036366a6b942f1d12c5853b0328077b5 100644 (file)
--- a/src/runtime/proc.c
+++ b/src/runtime/proc.c
@@ -2436,7 +2436,7 @@ extern byte runtime·etext[];
 void
 runtime·sigprof(uint8 *pc, uint8 *sp, uint8 *lr, G *gp, M *mp)
 {
-       int32 n;
+       int32 n, off;
        bool traceback;
        // Do not use global m in this function, use mp instead.
        // On windows one m is sending reports about all the g's, so m means a wrong thing.
@@ -2530,9 +2530,20 @@ runtime·sigprof(uint8 *pc, uint8 *sp, uint8 *lr, G *gp, M *mp)
           ((uint8*)runtime·gogo <= pc && pc < (uint8*)runtime·gogo + RuntimeGogoBytes))
                traceback = false;
 
+       off = 0;
+       if(gp == mp->g0 && mp->curg != nil) {
+               stk[0] = (uintptr)pc;
+               off = 1;
+               gp = mp->curg;
+               pc = (uint8*)gp->sched.pc;
+               sp = (uint8*)gp->sched.sp;
+               lr = 0;
+               traceback = true;
+       }
+
        n = 0;
        if(traceback)
-               n = runtime·gentraceback((uintptr)pc, (uintptr)sp, (uintptr)lr, gp, 0, stk, nelem(stk), nil, nil, false);
+               n = runtime·gentraceback((uintptr)pc, (uintptr)sp, (uintptr)lr, gp, 0, stk+off, nelem(stk)-off, nil, nil, false);
        if(!traceback || n <= 0) {
                // Normal traceback is impossible or has failed.
                // See if it falls into several common cases.