runtime/trace: enable frame pointer unwinding by default for amd64 and arm64

Re-enable frame pointer unwinding for execution tracing on amd64 by
default, now that CL 489015 and CL 488755 have fixed recently-discovered
crashes. This reverts CL 486382.

These fixes, together with CL 241158 to fix up frame pointers when
copying stacks on arm64, also make frame pointer unwinding for tracing
safe to enable for arm64. This should significantly reduce the CPU and
latency overhead of execution tracing on arm64, as it has for amd64.

Co-Authored-By: Felix Geisendörfer <felix.geisendoerfer@datadoghq.com>
Change-Id: I64a88bd69dfd8cb13956ec46f8b1203dbeaa26a6
Reviewed-on: https://go-review.googlesource.com/c/go/+/490815
Reviewed-by: Felix Geisendörfer <felix.geisendoerfer@datadoghq.com>
Run-TryBot: Nick Ripley <nick.ripley@datadoghq.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>
Auto-Submit: Michael Pratt <mpratt@google.com>

diff --git a/src/runtime/runtime1.go b/src/runtime/runtime1.go
index 7dc65bdcc1ce4c2521985b490427b01ce9ed0480..65bed433c3e0f9d7f490a3cc82d4c1aa23a6ff42 100644 (file)
--- a/src/runtime/runtime1.go
+++ b/src/runtime/runtime1.go
@@ -369,7 +369,6 @@ func parsedebugvars() {
        debug.cgocheck = 1
        debug.invalidptr = 1
        debug.adaptivestackstart = 1 // set this to 0 to turn larger initial goroutine stacks off
-       debug.tracefpunwindoff = 1   // Frame pointer unwinding sometimes crashes on amd64. See issue 59692.
        if GOOS == "linux" {
                // On Linux, MADV_FREE is faster than MADV_DONTNEED,
                // but doesn't affect many of the statistics that

diff --git a/src/runtime/trace.go b/src/runtime/trace.go
index 79ccebb4b31736c8e2546efe2dd408a251436f4c..5eb68271d10e6c36c49d2cadf9bea3873c4fdcfa 100644 (file)
--- a/src/runtime/trace.go
+++ b/src/runtime/trace.go
@@ -927,12 +927,10 @@ func traceStackID(mp *m, pcBuf []uintptr, skip int) uint64 {
        return uint64(id)
 }
 
-// tracefpunwindoff returns false if frame pointer unwinding for the tracer is
+// tracefpunwindoff returns true if frame pointer unwinding for the tracer is
 // disabled via GODEBUG or not supported by the architecture.
 func tracefpunwindoff() bool {
-       // compiler emits frame pointers for amd64 and arm64, but issue 58432 blocks
-       // arm64 support for now.
-       return debug.tracefpunwindoff != 0 || goarch.ArchFamily != goarch.AMD64
+       return debug.tracefpunwindoff != 0 || (goarch.ArchFamily != goarch.AMD64 && goarch.ArchFamily != goarch.ARM64)
 }
 
 // fpTracebackPCs populates pcBuf with the return addresses for each frame and