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35c7234601
This adds a maymorestack hook that forces a preemption at every possible cooperative preemption point. This would have helped us catch several recent preemption-related bugs earlier, including #47302, #47304, and #47441. For #48297. Change-Id: Ib82c973589c8a7223900e1842913b8591938fb9f Reviewed-on: https://go-review.googlesource.com/c/go/+/359796 Trust: Austin Clements <austin@google.com> Run-TryBot: Austin Clements <austin@google.com> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Cherry Mui <cherryyz@google.com> Reviewed-by: Michael Pratt <mpratt@google.com> Reviewed-by: David Chase <drchase@google.com>
97 lines
2.8 KiB
Go
97 lines
2.8 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package runtime
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import (
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"runtime/internal/atomic"
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"unsafe"
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)
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// GOMAXPROCS sets the maximum number of CPUs that can be executing
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// simultaneously and returns the previous setting. It defaults to
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// the value of runtime.NumCPU. If n < 1, it does not change the current setting.
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// This call will go away when the scheduler improves.
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func GOMAXPROCS(n int) int {
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if GOARCH == "wasm" && n > 1 {
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n = 1 // WebAssembly has no threads yet, so only one CPU is possible.
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}
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lock(&sched.lock)
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ret := int(gomaxprocs)
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unlock(&sched.lock)
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if n <= 0 || n == ret {
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return ret
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}
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stopTheWorldGC("GOMAXPROCS")
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// newprocs will be processed by startTheWorld
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newprocs = int32(n)
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startTheWorldGC()
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return ret
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}
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// NumCPU returns the number of logical CPUs usable by the current process.
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//
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// The set of available CPUs is checked by querying the operating system
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// at process startup. Changes to operating system CPU allocation after
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// process startup are not reflected.
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func NumCPU() int {
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return int(ncpu)
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}
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// NumCgoCall returns the number of cgo calls made by the current process.
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func NumCgoCall() int64 {
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var n = int64(atomic.Load64(&ncgocall))
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for mp := (*m)(atomic.Loadp(unsafe.Pointer(&allm))); mp != nil; mp = mp.alllink {
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n += int64(mp.ncgocall)
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}
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return n
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}
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// NumGoroutine returns the number of goroutines that currently exist.
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func NumGoroutine() int {
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return int(gcount())
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}
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//go:linkname debug_modinfo runtime/debug.modinfo
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func debug_modinfo() string {
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return modinfo
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}
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// mayMoreStackPreempt is a maymorestack hook that forces a preemption
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// at every possible cooperative preemption point.
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//
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// This is valuable to apply to the runtime, which can be sensitive to
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// preemption points. To apply this to all preemption points in the
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// runtime and runtime-like code, use the following in bash or zsh:
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//
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// X=(-{gc,asm}flags={runtime/...,reflect,sync}=-d=maymorestack=runtime.mayMoreStackPreempt) GOFLAGS=${X[@]}
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//
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// This must be deeply nosplit because it is called from a function
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// prologue before the stack is set up and because the compiler will
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// call it from any splittable prologue (leading to infinite
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// recursion).
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//
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// Ideally it should also use very little stack because the linker
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// doesn't currently account for this in nosplit stack depth checking.
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//
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//go:nosplit
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//
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// Ensure mayMoreStackPreempt can be called for all ABIs.
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//
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//go:linkname mayMoreStackPreempt
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func mayMoreStackPreempt() {
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// Don't do anything on the g0 or gsignal stack.
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g := getg()
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if g == g.m.g0 || g == g.m.gsignal {
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return
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}
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// Force a preemption, unless the stack is already poisoned.
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if g.stackguard0 < stackPoisonMin {
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g.stackguard0 = stackPreempt
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}
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}
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