From c6388d381ee4b62c56b499bc8a8d3127af86faa3 Mon Sep 17 00:00:00 2001 From: Austin Clements Date: Thu, 24 Aug 2017 15:06:26 -0400 Subject: [PATCH] [release-branch.go1.9] runtime: capture runtimeInitTime after nanotime is initialized CL 36428 changed the way nanotime works so on Darwin and Windows it now depends on runtime.startNano, which is computed at runtime.init time. Unfortunately, the `runtimeInitTime = nanotime()` initialization happened *before* runtime.init, so on these platforms runtimeInitTime is set incorrectly. The one (and only) consequence of this is that the start time printed in gctrace lines is bogus: gc 1 18446653480.186s 0%: 0.092+0.47+0.038 ms clock, 0.37+0.15/0.81/1.8+0.15 ms cpu, 4->4->1 MB, 5 MB goal, 8 P To fix this, this commit moves the runtimeInitTime initialization to shortly after runtime.init, at which point nanotime is safe to use. This also requires changing the condition in newproc1 that currently uses runtimeInitTime != 0 simply to detect whether or not the main M has started. Since runtimeInitTime could genuinely be 0 now, this introduces a separate flag to newproc1. Fixes #21554. Change-Id: Id874a4b912d3fa3d22f58d01b31ffb3548266d3b Reviewed-on: https://go-review.googlesource.com/58690 Run-TryBot: Austin Clements TryBot-Result: Gobot Gobot Reviewed-by: Rick Hudson Reviewed-by: Ian Lance Taylor Reviewed-on: https://go-review.googlesource.com/70848 Run-TryBot: Russ Cox Reviewed-by: Austin Clements --- src/runtime/proc.go | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/src/runtime/proc.go b/src/runtime/proc.go index ed333bb92e..a631a016a3 100644 --- a/src/runtime/proc.go +++ b/src/runtime/proc.go @@ -96,6 +96,9 @@ var main_init_done chan bool //go:linkname main_main main.main func main_main() +// mainStarted indicates that the main M has started. +var mainStarted bool + // runtimeInitTime is the nanotime() at which the runtime started. var runtimeInitTime int64 @@ -119,8 +122,8 @@ func main() { maxstacksize = 250000000 } - // Record when the world started. - runtimeInitTime = nanotime() + // Allow newproc to start new Ms. + mainStarted = true systemstack(func() { newm(sysmon, nil) @@ -148,6 +151,10 @@ func main() { } }() + // Record when the world started. Must be after runtime_init + // because nanotime on some platforms depends on startNano. + runtimeInitTime = nanotime() + gcenable() main_init_done = make(chan bool) @@ -3024,7 +3031,7 @@ func newproc1(fn *funcval, argp *uint8, narg int32, nret int32, callerpc uintptr } runqput(_p_, newg, true) - if atomic.Load(&sched.npidle) != 0 && atomic.Load(&sched.nmspinning) == 0 && runtimeInitTime != 0 { + if atomic.Load(&sched.npidle) != 0 && atomic.Load(&sched.nmspinning) == 0 && mainStarted { wakep() } _g_.m.locks-- -- 2.48.1