head -r325700 to -r325997: problem locking/unlocking/<something> for (at least) amd64?

Ever since I updated from -r325700 to -r325997 I've been
having odd, non-repeatable, fairly rare problems on amd64.
(I've yet to see if I get similar issues on other
platforms.)

I've reported a couple of panic for page faults in
kernel mode in other list messages.

But I'm also getting things like clang failing assertions
that do not repeat when the compile is simply retried with
the same input files.

I only mention locking because of recent head/sys/kern
activity between -r325700 and -r325997, the intermittent
nature of the observed failures, and the wide variety of
contexts (kernel, world). I do not have specific evidence
of a specific cause. (I do not see how I'm ever going to
get any such evidence.)

The following error did not repeat on a simple retry
of the compile:

--- Sema/SemaDeclAttr.o ---
Assertion failed: (I->second && I->first == I->second->getValPtr() && "List invariant broken!"), function AddToUseList, file /usr/src/contrib/llvm/lib/IR/Value.cpp, line 793.
c++: error: unable to execute command: Abort trap (core dumped)
c++: error: clang frontend command failed due to signal (use -v to see invocation)
FreeBSD clang version 5.0.0 (tags/RELEASE_500/final 312559) (based on LLVM 5.0.0svn)
Target: powerpc-unknown-freebsd12.0
Thread model: posix
InstalledDir: /usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp/usr/bin
c++: note: diagnostic msg: PLEASE submit a bug report to https://bugs.freebsd.org/submit/ and include the crash backtrace, preprocessed source, and associated run script.
Building /usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/lib/clang/libclang/Sema/SemaExceptionSpec.o
c++: note: diagnostic msg: 
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
c++: note: diagnostic msg: /tmp/SemaDeclAttr-6b7ba8.cpp
c++: note: diagnostic msg: /tmp/SemaDeclAttr-6b7ba8.sh
c++: note: diagnostic msg: 

********************
*** [Sema/SemaDeclAttr.o] Error code 254

make[6]: stopped in /usr/src/lib/clang/libclang
.ERROR_TARGET='Sema/SemaDeclAttr.o'
.ERROR_META_FILE='/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/lib/clang/libclang/Sema_SemaDeclAttr.o.meta'
.MAKE.LEVEL='6'
MAKEFILE=''
.MAKE.MODE='meta missing-filemon=yes missing-meta=yes silent=yes verbose'
_ERROR_CMD='c++  -target powerpc-unknown-freebsd12.0 --sysroot=/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp -B/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp/usr/bin  -O2 -pipe -I/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/lib/clang/libclang -I/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/lib/clang/libllvm -I/usr/src/contrib/llvm/tools/clang/lib/Driver -I/usr/src/contrib/llvm/tools/clang/include -DCLANG_ENABLE_ARCMT -DCLANG_ENABLE_STATIC_ANALYZER -I/usr/src/lib/clang/include -I/usr/src/contrib/llvm/include -DLLVM_BUILD_GLOBAL_ISEL -D__STDC_LIMIT_MACROS -D__STDC_CONSTANT_MACROS -DLLVM_DEFAULT_TARGET_TRIPLE=\"powerpc-unknown-freebsd12.0\" -DLLVM_HOST_TRIPLE=\"powerpc-unknown-freebsd12.0\" -DDEFAULT_SYSROOT=\"\" -ffunction-sections -fdata-sections -gline-tables-only -fstack-protector-strong -Qunused-arguments  -std=c++11 -fno-exceptions -fno-rtti -gline-tables-only -stdlib=libc++ -Wno-c++11-extensions  -c /usr/src/contrib/llvm/tools/clang/lib/Sema/SemaDeclAttr.cpp -o Sema/SemaDeclAttr.o;'
.CURDIR='/usr/src/lib/clang/libclang'
.MAKE='make'
.OBJDIR='/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/lib/clang/libclang'
.TARGETS='all'
DESTDIR='/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp'
LD_LIBRARY_PATH=''
MACHINE='powerpc'
MACHINE_ARCH='powerpc'
MAKEOBJDIRPREFIX=''
MAKESYSPATH='/usr/src/share/mk'
MAKE_VERSION='20171028'
PATH='/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp/legacy/usr/sbin:/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp/legacy/usr/bin:/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp/legacy/bin:/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp/usr/sbin:/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp/usr/bin:/sbin:/bin:/usr/sbin:/usr/bin'
SRCTOP='/usr/src'
OBJTOP='/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc'
.MAKE.MAKEFILES='/usr/src/share/mk/sys.mk /usr/src/share/mk/local.sys.env.mk /usr/src/share/mk/src.sys.env.mk /root/src.configs/src.conf.powerpc-clang-bootstrap.amd64-host /usr/src/share/mk/bsd.mkopt.mk /usr/src/share/mk/src.sys.obj.mk /usr/src/share/mk/auto.obj.mk /usr/src/share/mk/bsd.suffixes.mk /root/src.configs/make.conf /usr/src/share/mk/local.sys.mk /usr/src/share/mk/src.sys.mk /dev/null /usr/src/lib/clang/libclang/Makefile /usr/src/share/mk/src.opts.mk /usr/src/share/mk/bsd.own.mk /usr/src/share/mk/bsd.opts.mk /usr/src/share/mk/bsd.cpu.mk /usr/src/share/mk/bsd.compiler.mk /usr/src/share/mk/bsd.linker.mk /usr/src/lib/clang/clang.pre.mk /usr/src/lib/clang/llvm.pre.mk /usr/src/lib/clang/clang.build.mk /usr/src/lib/clang/llvm.build.mk /usr/src/share/mk/bsd.lib.mk /usr/src/share/mk/bsd.init.mk /usr/src/share/mk/local.init.mk /usr/src/share/mk/src.init.mk /usr/src/lib/clang/libclang/../Makefile.inc /usr/src/share/mk/bsd.libnames.mk /usr/src/share/mk/src.libnames.mk /usr/src/share/mk/bsd.symver.mk /usr/src/share/mk/bsd.nls.mk /usr/src/share/mk/bsd.files.mk /usr/src/share/mk/bsd.incs.mk /usr/src/share/mk/bsd.confs.mk /usr/src/share/mk/bsd.links.mk /usr/src/share/mk/bsd.dep.mk /usr/src/share/mk/bsd.clang-analyze.mk /usr/src/share/mk/bsd.obj.mk /usr/src/share/mk/bsd.subdir.mk /usr/src/share/mk/bsd.sys.mk'
.PATH='. /usr/src/lib/clang/libclang /usr/src/contrib/llvm/tools/clang/lib'
1 error

make[6]: stopped in /usr/src/lib/clang/libclang
.ERROR_TARGET='Sema/SemaDeclAttr.o'
.ERROR_META_FILE='/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/lib/clang/libclang/Sema_SemaDeclAttr.o.meta'
.MAKE.LEVEL='6'
MAKEFILE=''
.MAKE.MODE='meta missing-filemon=yes missing-meta=yes silent=yes verbose'
_ERROR_CMD='c++  -target powerpc-unknown-freebsd12.0 --sysroot=/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp -B/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp/usr/bin  -O2 -pipe -I/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/lib/clang/libclang -I/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/lib/clang/libllvm -I/usr/src/contrib/llvm/tools/clang/lib/Driver -I/usr/src/contrib/llvm/tools/clang/include -DCLANG_ENABLE_ARCMT -DCLANG_ENABLE_STATIC_ANALYZER -I/usr/src/lib/clang/include -I/usr/src/contrib/llvm/include -DLLVM_BUILD_GLOBAL_ISEL -D__STDC_LIMIT_MACROS -D__STDC_CONSTANT_MACROS -DLLVM_DEFAULT_TARGET_TRIPLE=\"powerpc-unknown-freebsd12.0\" -DLLVM_HOST_TRIPLE=\"powerpc-unknown-freebsd12.0\" -DDEFAULT_SYSROOT=\"\" -ffunction-sections -fdata-sections -gline-tables-only -fstack-protector-strong -Qunused-arguments  -std=c++11 -fno-exceptions -fno-rtti -gline-tables-only -stdlib=libc++ -Wno-c++11-extensions  -c /usr/src/contrib/llvm/tools/clang/lib/Sema/SemaDeclAttr.cpp -o Sema/SemaDeclAttr.o;'
.CURDIR='/usr/src/lib/clang/libclang'
.MAKE='make'
.OBJDIR='/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/lib/clang/libclang'
.TARGETS='all'
DESTDIR='/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp'
LD_LIBRARY_PATH=''
MACHINE='powerpc'
MACHINE_ARCH='powerpc'
MAKEOBJDIRPREFIX=''
MAKESYSPATH='/usr/src/share/mk'
MAKE_VERSION='20171028'
PATH='/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp/legacy/usr/sbin:/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp/legacy/usr/bin:/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp/legacy/bin:/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp/usr/sbin:/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp/usr/bin:/sbin:/bin:/usr/sbin:/usr/bin'
SRCTOP='/usr/src'
OBJTOP='/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc'
.MAKE.MAKEFILES='/usr/src/share/mk/sys.mk /usr/src/share/mk/local.sys.env.mk /usr/src/share/mk/src.sys.env.mk /root/src.configs/src.conf.powerpc-clang-bootstrap.amd64-host /usr/src/share/mk/bsd.mkopt.mk /usr/src/share/mk/src.sys.obj.mk /usr/src/share/mk/auto.obj.mk /usr/src/share/mk/bsd.suffixes.mk /root/src.configs/make.conf /usr/src/share/mk/local.sys.mk /usr/src/share/mk/src.sys.mk /dev/null /usr/src/lib/clang/libclang/Makefile /usr/src/share/mk/src.opts.mk /usr/src/share/mk/bsd.own.mk /usr/src/share/mk/bsd.opts.mk /usr/src/share/mk/bsd.cpu.mk /usr/src/share/mk/bsd.compiler.mk /usr/src/share/mk/bsd.linker.mk /usr/src/lib/clang/clang.pre.mk /usr/src/lib/clang/llvm.pre.mk /usr/src/lib/clang/clang.build.mk /usr/src/lib/clang/llvm.build.mk /usr/src/share/mk/bsd.lib.mk /usr/src/share/mk/bsd.init.mk /usr/src/share/mk/local.init.mk /usr/src/share/mk/src.init.mk /usr/src/lib/clang/libclang/../Makefile.inc /usr/src/share/mk/bsd.libnames.mk /usr/src/share/mk/src.libnames.mk /usr/src/share/mk/bsd.symver.mk /usr/src/share/mk/bsd.nls.mk /usr/src/share/mk/bsd.files.mk /usr/src/share/mk/bsd.incs.mk /usr/src/share/mk/bsd.confs.mk /usr/src/share/mk/bsd.links.mk /usr/src/share/mk/bsd.dep.mk /usr/src/share/mk/bsd.clang-analyze.mk /usr/src/share/mk/bsd.obj.mk /usr/src/share/mk/bsd.subdir.mk /usr/src/share/mk/bsd.sys.mk'
.PATH='. /usr/src/lib/clang/libclang /usr/src/contrib/llvm/tools/clang/lib'
*** [all_subdir_lib/clang/libclang] Error code 2

make[5]: stopped in /usr/src/lib/clang
.ERROR_TARGET='all_subdir_lib/clang/libclang'
.ERROR_META_FILE=''
.MAKE.LEVEL='5'
MAKEFILE=''
.MAKE.MODE='meta missing-filemon=yes missing-meta=yes silent=yes verbose'
_ERROR_CMD='.PHONY'
.CURDIR='/usr/src/lib/clang'
.MAKE='make'
.OBJDIR='/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/lib/clang'
.TARGETS='all'
DESTDIR='/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp'
LD_LIBRARY_PATH=''
MACHINE='powerpc'
MACHINE_ARCH='powerpc'
MAKEOBJDIRPREFIX=''
MAKESYSPATH='/usr/src/share/mk'
MAKE_VERSION='20171028'
PATH='/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp/legacy/usr/sbin:/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp/legacy/usr/bin:/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp/legacy/bin:/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp/usr/sbin:/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp/usr/bin:/sbin:/bin:/usr/sbin:/usr/bin'
SRCTOP='/usr/src'
OBJTOP='/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc'
.MAKE.MAKEFILES='/usr/src/share/mk/sys.mk /usr/src/share/mk/local.sys.env.mk /usr/src/share/mk/src.sys.env.mk /root/src.configs/src.conf.powerpc-clang-bootstrap.amd64-host /usr/src/share/mk/bsd.mkopt.mk /usr/src/share/mk/src.sys.obj.mk /usr/src/share/mk/auto.obj.mk /usr/src/share/mk/bsd.suffixes.mk /root/src.configs/make.conf /usr/src/share/mk/local.sys.mk /usr/src/share/mk/src.sys.mk /dev/null /usr/src/lib/clang/Makefile /usr/src/share/mk/src.opts.mk /usr/src/share/mk/bsd.own.mk /usr/src/share/mk/bsd.opts.mk /usr/src/share/mk/bsd.cpu.mk /usr/src/share/mk/bsd.compiler.mk /usr/src/share/mk/bsd.linker.mk /usr/src/share/mk/bsd.subdir.mk /usr/src/share/mk/bsd.init.mk /usr/src/share/mk/local.init.mk /usr/src/share/mk/src.init.mk /usr/src/lib/clang/../Makefile.inc'
.PATH='. /usr/src/lib/clang'
1 error

make[5]: stopped in /usr/src/lib/clang
.ERROR_TARGET='all_subdir_lib/clang/libclang'
.ERROR_META_FILE=''
.MAKE.LEVEL='5'
MAKEFILE=''
.MAKE.MODE='meta missing-filemon=yes missing-meta=yes silent=yes verbose'
_ERROR_CMD='.PHONY'
.CURDIR='/usr/src/lib/clang'
.MAKE='make'
.OBJDIR='/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/lib/clang'
.TARGETS='all'
DESTDIR='/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp'
LD_LIBRARY_PATH=''
MACHINE='powerpc'
MACHINE_ARCH='powerpc'
MAKEOBJDIRPREFIX=''
MAKESYSPATH='/usr/src/share/mk'
MAKE_VERSION='20171028'
PATH='/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp/legacy/usr/sbin:/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp/legacy/usr/bin:/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp/legacy/bin:/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp/usr/sbin:/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc/tmp/usr/bin:/sbin:/bin:/usr/sbin:/usr/bin'
SRCTOP='/usr/src'
OBJTOP='/usr/obj/powerpcvtsc_clang/powerpc.powerpc/usr/src/powerpc.powerpc'
.MAKE.MAKEFILES='/usr/src/share/mk/sys.mk /usr/src/share/mk/local.sys.env.mk /usr/src/share/mk/src.sys.env.mk /root/src.configs/src.conf.powerpc-clang-bootstrap.amd64-host /usr/src/share/mk/bsd.mkopt.mk /usr/src/share/mk/src.sys.obj.mk /usr/src/share/mk/auto.obj.mk /usr/src/share/mk/bsd.suffixes.mk /root/src.configs/make.conf /usr/src/share/mk/local.sys.mk /usr/src/share/mk/src.sys.mk /dev/null /usr/src/lib/clang/Makefile /usr/src/share/mk/src.opts.mk /usr/src/share/mk/bsd.own.mk /usr/src/share/mk/bsd.opts.mk /usr/src/share/mk/bsd.cpu.mk /usr/src/share/mk/bsd.compiler.mk /usr/src/share/mk/bsd.linker.mk /usr/src/share/mk/bsd.subdir.mk /usr/src/share/mk/bsd.init.mk /usr/src/share/mk/local.init.mk /usr/src/share/mk/src.init.mk /usr/src/lib/clang/../Makefile.inc'
.PATH='. /usr/src/lib/clang'
*** [all_subdir_lib/clang] Error code 2


===
Mark Millard
markmi at dsl-only.net