runtime: "runtime: bad pointer in frame runtime.sellock" crash on some builders #15936
Description
While working on another builder crash, I noticed this once:
https://build.golang.org/log/e3cc1e2bd6c5d4e0c3726213974c3d0a1af12f5a
runtime: bad pointer in frame runtime.sellock at 0xa24cc68: 0xd
fatal error: invalid stack pointer
runtime stack:
runtime.throw(0x424be8a, 0x15)
/private/var/folders/0m/n0150xb53y5cg1rq75_3qv3r0000gn/T/workdir/go/src/runtime/panic.go:566 +0x80 fp=0x16fd5f2a0 sp=0x16fd5f280
runtime.adjustpointers(0xa24cc68, 0x16fd5f440, 0x16fd5f7b8, 0x4285c58)
/private/var/folders/0m/n0150xb53y5cg1rq75_3qv3r0000gn/T/workdir/go/src/runtime/stack.go:602 +0x2d8 fp=0x16fd5f3b0 sp=0x16fd5f2a0
runtime.adjustframe(0x16fd5f6c0, 0x16fd5f7b8, 0x16fd5f501)
/private/var/folders/0m/n0150xb53y5cg1rq75_3qv3r0000gn/T/workdir/go/src/runtime/stack.go:674 +0x1d0 fp=0x16fd5f470 sp=0x16fd5f3b0
runtime.gentraceback(0x4103e50, 0xa24ca60, 0x40d9aa8, 0xa1ed380, 0x0, 0x0, 0x7fffffff, 0x425e8c0, 0x16fd5f7b8, 0x0, ...)
/private/var/folders/0m/n0150xb53y5cg1rq75_3qv3r0000gn/T/workdir/go/src/runtime/traceback.go:378 +0xe0c fp=0x16fd5f710 sp=0x16fd5f470
runtime.copystack(0xa1ed380, 0x1000, 0xa1ed301)
/private/var/folders/0m/n0150xb53y5cg1rq75_3qv3r0000gn/T/workdir/go/src/runtime/stack.go:895 +0x3e0 fp=0x16fd5f920 sp=0x16fd5f710
runtime.newstack()
/private/var/folders/0m/n0150xb53y5cg1rq75_3qv3r0000gn/T/workdir/go/src/runtime/stack.go:1063 +0xa80 fp=0x16fd5faa0 sp=0x16fd5f920
runtime.morestack()
/private/var/folders/0m/n0150xb53y5cg1rq75_3qv3r0000gn/T/workdir/go/src/runtime/asm_arm64.s:300 +0x5c fp=0x16fd5faa0 sp=0x16fd5faa0
Filing this issue if the crash is interesting in itself or in case in happens again on the same or another builder.