On 11.12.18 22:01, Cherry Zhang wrote: > On Tue, Dec 11, 2018 at 3:51 PM Ian Lance Taylor <i...@golang.org> wrote: > >> On Tue, Dec 11, 2018 at 6:52 AM Matthias Klose <d...@ubuntu.com> wrote: >>> >>> On 10.12.18 16:54, Cherry Zhang wrote: >>>> On Mon, Dec 10, 2018 at 1:41 AM Matthias Klose <d...@ubuntu.com> >> wrote: >>>> >>>>> On 06.12.18 00:09, Ian Lance Taylor wrote: >>>>>> This libgo patch by Cherry Zhang adds support for precise stack >>>>>> scanning to the Go runtime. This uses per-function stack maps stored >>>>>> in the exception tables in the language-specific data area. The >>>>>> compiler needs to generate these stack maps; currently this is only >>>>>> done by a version of LLVM, not by GCC. Each safepoint in a function >>>>>> is associated with a (real or dummy) landing pad, and its "type info" >>>>>> in the exception table is a pointer to the stack map. When a stack is >>>>>> scanned, the stack map is found by the stack unwinding code. >>>>>> >>>>>> For precise stack scan we need to unwind the stack. There are three >>>>> cases: >>>>>> >>>>>> - If a goroutine is scanning its own stack, it can unwind the stack >>>>>> and scan the frames. >>>>>> >>>>>> - If a goroutine is scanning another, stopped, goroutine, it cannot >>>>>> directly unwind the target stack. We handle this by switching >>>>>> (runtime.gogo) to the target g, letting it unwind and scan the stack, >>>>>> and switch back. >>>>>> >>>>>> - If we are scanning a goroutine that is blocked in a syscall, we >> send >>>>>> a signal to the target goroutine's thread, and let the signal handler >>>>>> unwind and scan the stack. Extra care is needed as this races with >>>>>> enter/exit syscall. >>>>>> >>>>>> Currently this is only implemented on GNU/Linux. >>>>>> >>>>>> Bootstrapped and ran Go testsuite on x86_64-pc-linux-gnu. Committed >>>>>> to mainline. >>>>> >>>>> this broke the libgo build on ARM32: >>>>> >>>>> ../../../src/libgo/runtime/go-unwind.c: In function >>>>> 'scanstackwithmap_callback': >>>>> ../../../src/libgo/runtime/go-unwind.c:754:18: error: >> '_URC_NORMAL_STOP' >>>>> undeclared (first use in this function) >>>>> 754 | return _URC_NORMAL_STOP; >>>>> | ^~~~~~~~~~~~~~~~ >>>>> ../../../src/libgo/runtime/go-unwind.c:754:18: note: each undeclared >>>>> identifier >>>>> is reported only once for each function i >>>>> t appears in >>>>> ../../../src/libgo/runtime/go-unwind.c: In function >>>>> 'probestackmaps_callback': >>>>> ../../../src/libgo/runtime/go-unwind.c:802:10: error: >> '_URC_NORMAL_STOP' >>>>> undeclared (first use in this function) >>>>> 802 | return _URC_NORMAL_STOP; >>>>> | ^~~~~~~~~~~~~~~~ >>>>> ../../../src/libgo/runtime/go-unwind.c:803:1: warning: control >> reaches end >>>>> of >>>>> non-void function [-Wreturn-type] >>>>> 803 | } >>>>> | ^ >>>>> make[6]: *** [Makefile:1474: runtime/go-unwind.lo] Error 1 >>>>> make[6]: Leaving directory >>>>> '/<<PKGBUILDDIR>>/build/arm-linux-gnueabihf/libgo' >>>>> >>>>> >>>> Hell Matthias, >>>> >>>> Thank you for the report. And sorry about the breakage. Does >>>> https://go-review.googlesource.com/c/gofrontend/+/153417 (or the patch >>>> below) fix ARM32 build? I don't have an ARM32 machine at hand to test. >>> >>> this fixes the build. >>> >>> currently running the testsuite, almost every test case core dumps on >>> arm-linux-gnueabihf >> >> I committed Cherry's patch to trunk, since it looks reasonable to me. >> Cherry, Matthias, let me know if you figure out why programs are >> failing. >> >> > Thank you. > > I don't know for the moment. I'm trying to find an ARM32 machine so I can > test. > > Matthias, is it convenient for you to share a stack trace for the failing > programs? That would be very helpful. Thanks!
I'll do a local build this weekend. For now you find the build log at https://launchpad.net/ubuntu/+source/gcc-snapshot/1:20181210-0ubuntu1/+build/15759748
