[Bug go/89199] New: libgo intermittent testcase failures on ppc64le power9 after r268458

[boger at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89199

            Bug ID: 89199
           Summary: libgo intermittent testcase failures on ppc64le power9
                    after r268458
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: go
          Assignee: ian at airs dot com
          Reporter: boger at gcc dot gnu.org
                CC: cmang at google dot com, wschmidt at gcc dot gnu.org
  Target Milestone: ---

Some new intermittent testcase failures started appearing in gcc-testresults
for libgo starting with commit 268458 on power9 systems. I have verified this
is the commit where the failures begin. We have not seen these failures on
Ubuntu 18.04 power8 with the same commit.

In some test runs, there are failures in cmd/go/internal/mvs, net/http,
net/http/httputil, sync and they have panic output with the same message about
sync.Cond as shown below in the panic trace.

I have run the tests on our 2 power9 systems which are both Ubuntu 18.04 and
when built with a specific commit the binary will consistently fail.

panic: sync.Cond is copied

goroutine 348 [running]:
sync.copyChecker.check
       
/home/boger/gccgo.work/bld/powerpc64le-linux/libgo/gotest163361/test/cond.go:85
sync.copyChecker.check
       
/home/boger/gccgo.work/bld/powerpc64le-linux/libgo/gotest163361/test/cond.go:81
sync.Cond.Wait
       
/home/boger/gccgo.work/bld/powerpc64le-linux/libgo/gotest163361/test/cond.go:53
sync_test.TestCondSignalStealing..func1
       
/home/boger/gccgo.work/bld/powerpc64le-linux/libgo/gotest163361/test/cond_test.go:197
created by sync_test.TestCondSignalStealing
       
/home/boger/gccgo.work/bld/powerpc64le-linux/libgo/gotest163361/test/cond_test.go:194
+472
Keeping gotest163361
FAIL: sync

To run an individual test I do:

cd bld/powerpc64le-linux/libgo
make sync/check