go: runtime: frequent crashes in unlock2 on NetBSD and OpenBSD since 2021-10-07

I believe some of the logs above show this as well, but it hasn’t yet been pointed out that this crash sometimes occurs in the Go 1.4 bootstrap toolchain as well. Example below.

The line numbers here don’t quite line up to the mp.nextwaitm line (src/runtime/lock_sema.go:107 in a comment in the copy of 1.4 I’m looking at), but it seems likely to be the same.

IMO, this indicates that we either have a bug that has been around since at least 1.4, or there is some more general system-provoked memory corruption going on.

fatal error: unexpected signal during runtime execution
[signal SIGSEGV: segmentation violation code=0x1 addr=0x1f8 pc=0x80553c7]

goroutine 20 [running]:
runtime.throw(0x8428440, 0x2a)
        /home/bradfitz/go-netbsd-386-bootstrap/src/runtime/panic.go:616 +0x6b fp=0x18971444 sp=0x18971438 pc=0x806e24b
runtime.sigpanic()
        /home/bradfitz/go-netbsd-386-bootstrap/src/runtime/signal_unix.go:366 +0x230 fp=0x18971468 sp=0x18971444 pc=0x8081480
runtime.unlock(0xbba62f84)
        /home/bradfitz/go-netbsd-386-bootstrap/src/runtime/lock_sema.go:107 +0x97 fp=0x18971484 sp=0x18971468 pc=0x80553c7
internal/poll.runtime_pollOpen(0xb, 0x8442d54, 0x0)
        /home/bradfitz/go-netbsd-386-bootstrap/src/runtime/netpoll.go:120 +0xa2 fp=0x1897149c sp=0x18971484 pc=0x806ae92
internal/poll.(*pollDesc).init(0x18d081d4, 0x18d081c0, 0x18a64001, 0x18d081c0)
        /home/bradfitz/go-netbsd-386-bootstrap/src/internal/poll/fd_poll_runtime.go:37 +0x3a fp=0x189714bc sp=0x1897149c pc=0x80c2cea
internal/poll.(*FD).Init(0x18d081c0, 0x84161bd, 0x4, 0x1, 0x8, 0x18)
        /home/bradfitz/go-netbsd-386-bootstrap/src/internal/poll/fd_unix.go:58 +0x47 fp=0x189714d0 sp=0x189714bc pc=0x80c3787
os.newFile(0xb, 0x841804b, 0x9, 0x1, 0xb)
        /home/bradfitz/go-netbsd-386-bootstrap/src/os/file_unix.go:117 +0xd0 fp=0x189714f8 sp=0x189714d0 pc=0x80cb080
os.OpenFile(0x841804b, 0x9, 0x0, 0x0, 0x8, 0x18, 0x555)
        /home/bradfitz/go-netbsd-386-bootstrap/src/os/file_unix.go:198 +0xc4 fp=0x1897152c sp=0x189714f8 pc=0x80cb274
os.Open(0x841804b, 0x9, 0x57, 0xbba657ac, 0x0)
        /home/bradfitz/go-netbsd-386-bootstrap/src/os/file.go:241 +0x33 fp=0x1897154c sp=0x1897152c pc=0x80c95f3
os/exec.(*Cmd).stdin(0x18a7c000, 0x18bec160, 0x86296a0, 0xbbabe6c8)
        /home/bradfitz/go-netbsd-386-bootstrap/src/os/exec/exec.go:210 +0x3bb fp=0x189715b8 sp=0x1897154c pc=0x81153ab
os/exec.(*Cmd).Start(0x18a7c000, 0x18d260c0, 0x18bec420)
        /home/bradfitz/go-netbsd-386-bootstrap/src/os/exec/exec.go:363 +0xbf fp=0x18971664 sp=0x189715b8 pc=0x8115c5f
os/exec.(*Cmd).Run(0x18a7c000, 0x0, 0x0)
        /home/bradfitz/go-netbsd-386-bootstrap/src/os/exec/exec.go:297 +0x1b fp=0x18971674 sp=0x18971664 pc=0x8115b5b
cmd/go/internal/work.(*Builder).runOut(0x18bb0120, 0x18a3e960, 0x1b, 0x18a65c51, 0x4, 0x0, 0x0, 0x0, 0x18900d20, 0x11, ...)
        /home/bradfitz/go-netbsd-386-bootstrap/src/cmd/go/internal/work/exec.go:1422 +0x5cb fp=0x1897172c sp=0x18971674 pc=0x81f49ab
cmd/go/internal/work.(*Builder).run(0x18bb0120, 0x18ceab00, 0x18a3e960, 0x1b, 0x18a65c51, 0x4, 0x0, 0x0, 0x0, 0x18900d20, ...)
        /home/bradfitz/go-netbsd-386-bootstrap/src/cmd/go/internal/work/exec.go:1363 +0x81 fp=0x18971794 sp=0x1897172c pc=0x81f4091
cmd/go/internal/work.gcToolchain.asm(0x18bb0120, 0x18ceab00, 0x1897e680, 0x1a, 0x1a, 0x18971930, 0x2, 0x2, 0x18971b60, 0x4)
        /home/bradfitz/go-netbsd-386-bootstrap/src/cmd/go/internal/work/gc.go:236 +0x947 fp=0x18971900 sp=0x18971794 pc=0x8200927
cmd/go/internal/work.(*gcToolchain).asm(0x863b438, 0x18bb0120, 0x18ceab00, 0x1897e680, 0x1a, 0x1a, 0x4, 0x8415c20, 0x3, 0x18971ba0, ...)
        <autogenerated>:1 +0x4a fp=0x1897192c sp=0x18971900 pc=0x821194a
cmd/go/internal/work.(*Builder).build(0x18bb0120, 0x18ceab00, 0x0, 0x0)
        /home/bradfitz/go-netbsd-386-bootstrap/src/cmd/go/internal/work/exec.go:598 +0x2710 fp=0x18971f30 sp=0x1897192c pc=0x81ed090
cmd/go/internal/work.(*Builder).Do.func1(0x18ceab00)
        /home/bradfitz/go-netbsd-386-bootstrap/src/cmd/go/internal/work/exec.go:101 +0x56 fp=0x18971f70 sp=0x18971f30 pc=0x820fae6
cmd/go/internal/work.(*Builder).Do.func2(0x18ac47c0, 0x18bb0120, 0x18c3c500)
        /home/bradfitz/go-netbsd-386-bootstrap/src/cmd/go/internal/work/exec.go:159 +0x80 fp=0x18971fe0 sp=0x18971f70 pc=0x820fd40
runtime.goexit()
        /home/bradfitz/go-netbsd-386-bootstrap/src/runtime/asm_386.s:1665 +0x1 fp=0x18971fe4 sp=0x18971fe0 pc=0x8094531
created by cmd/go/internal/work.(*Builder).Do
        /home/bradfitz/go-netbsd-386-bootstrap/src/cmd/go/internal/work/exec.go:146 +0x2dc

Edit: The disassembly of the bootstrap compiler supports that this is the load of mp.nextwaitm.

Two OpenBSD crashes in unlock2 that do not involve updateTimerPMask:

https://build.golang.org/log/c6898314cb2fdaa7a39437c2186b5e8a804d47f3 https://build.golang.org/log/afdc1f994a11b5041fa0e3dff06cc4ce8c2070ef