The runtime_gc function in libgo invokes the garbage collector proper on the g0 thread (a thread with a large stack that is not involved in scheduling). This is done via runtime_mcall. Upon return from runtime_mcall, the caller may be running on a different thread. Unfortunately, the runtime_gc function called runtime_m to get the Go thread info, and did not refresh that value after calling runtime_mcall. The result mostly worked, but could fail in very busy program doing lots of work that started going as soon as the GC stopped. This patch fixes the problem. Bootstrapped and ran Go testsuite on x86_64-unknown-linux-gnu. Committed to mainline and 4.9 branch.
Ian
diff -r 52dcc874d3b7 libgo/runtime/mgc0.c --- a/libgo/runtime/mgc0.c Wed Aug 13 14:52:52 2014 -0700 +++ b/libgo/runtime/mgc0.c Fri Aug 15 15:07:02 2014 -0700 @@ -2204,6 +2204,7 @@ g->status = Gwaiting; g->waitreason = "garbage collection"; runtime_mcall(mgc); + m = runtime_m(); } // all done
