From f3b9f362c9f81fba61663002eac7f065afd9afd1 Mon Sep 17 00:00:00 2001 From: Elias Naur Date: Sun, 4 Nov 2018 09:36:25 +0100 Subject: [PATCH] [release-branch.go1.11] runtime: avoid arm64 8.1 atomics on Android The kernel on some Samsung S9+ models reports support for arm64 8.1 atomics, but in reality only some of the cores support them. Go programs scheduled to cores without support will crash with SIGILL. This change unconditionally disables the optimization on Android. A better fix is to precisely detect the offending chipset. Fixes #28586 Change-Id: I35a1273e5660603824d30ebef2ce7e429241bf1f Reviewed-on: https://go-review.googlesource.com/c/147377 Run-TryBot: Elias Naur TryBot-Result: Gobot Gobot Reviewed-by: Keith Randall Reviewed-on: https://go-review.googlesource.com/c/149557 Reviewed-by: Brad Fitzpatrick --- src/runtime/os_linux_arm64.go | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/src/runtime/os_linux_arm64.go b/src/runtime/os_linux_arm64.go index 28a0319f10736..59f3df47fee72 100644 --- a/src/runtime/os_linux_arm64.go +++ b/src/runtime/os_linux_arm64.go @@ -29,7 +29,17 @@ func archauxv(tag, val uintptr) { randomNumber = uint32(startupRandomData[4]) | uint32(startupRandomData[5])<<8 | uint32(startupRandomData[6])<<16 | uint32(startupRandomData[7])<<24 case _AT_HWCAP: - cpu_hwcap = uint(val) + // arm64 doesn't have a 'cpuid' instruction equivalent and relies on + // HWCAP/HWCAP2 bits for hardware capabilities. + hwcap := uint(val) + if GOOS == "android" { + // The Samsung S9+ kernel reports support for atomics, but not all cores + // actually support them, resulting in SIGILL. See issue #28431. + // TODO(elias.naur): Only disable the optimization on bad chipsets. + const hwcap_ATOMICS = 1 << 8 + hwcap &= ^uint(hwcap_ATOMICS) + } + cpu_hwcap = hwcap case _AT_HWCAP2: cpu_hwcap2 = uint(val) }