1// Copyright 2009 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package runtime
6
7import (
8	"internal/runtime/atomic"
9	"unsafe"
10)
11
12// GOMAXPROCS sets the maximum number of CPUs that can be executing
13// simultaneously and returns the previous setting. It defaults to
14// the value of [runtime.NumCPU]. If n < 1, it does not change the current setting.
15// This call will go away when the scheduler improves.
16func GOMAXPROCS(n int) int {
17	if GOARCH == "wasm" && n > 1 {
18		n = 1 // WebAssembly has no threads yet, so only one CPU is possible.
19	}
20
21	lock(&sched.lock)
22	ret := int(gomaxprocs)
23	unlock(&sched.lock)
24	if n <= 0 || n == ret {
25		return ret
26	}
27
28	stw := stopTheWorldGC(stwGOMAXPROCS)
29
30	// newprocs will be processed by startTheWorld
31	newprocs = int32(n)
32
33	startTheWorldGC(stw)
34	return ret
35}
36
37// NumCPU returns the number of logical CPUs usable by the current process.
38//
39// The set of available CPUs is checked by querying the operating system
40// at process startup. Changes to operating system CPU allocation after
41// process startup are not reflected.
42func NumCPU() int {
43	return int(ncpu)
44}
45
46// NumCgoCall returns the number of cgo calls made by the current process.
47func NumCgoCall() int64 {
48	var n = int64(atomic.Load64(&ncgocall))
49	for mp := (*m)(atomic.Loadp(unsafe.Pointer(&allm))); mp != nil; mp = mp.alllink {
50		n += int64(mp.ncgocall)
51	}
52	return n
53}
54
55func totalMutexWaitTimeNanos() int64 {
56	total := sched.totalMutexWaitTime.Load()
57
58	total += sched.totalRuntimeLockWaitTime.Load()
59	for mp := (*m)(atomic.Loadp(unsafe.Pointer(&allm))); mp != nil; mp = mp.alllink {
60		total += mp.mLockProfile.waitTime.Load()
61	}
62
63	return total
64}
65
66// NumGoroutine returns the number of goroutines that currently exist.
67func NumGoroutine() int {
68	return int(gcount())
69}
70
71//go:linkname debug_modinfo runtime/debug.modinfo
72func debug_modinfo() string {
73	return modinfo
74}
75
76// mayMoreStackPreempt is a maymorestack hook that forces a preemption
77// at every possible cooperative preemption point.
78//
79// This is valuable to apply to the runtime, which can be sensitive to
80// preemption points. To apply this to all preemption points in the
81// runtime and runtime-like code, use the following in bash or zsh:
82//
83//	X=(-{gc,asm}flags={runtime/...,reflect,sync}=-d=maymorestack=runtime.mayMoreStackPreempt) GOFLAGS=${X[@]}
84//
85// This must be deeply nosplit because it is called from a function
86// prologue before the stack is set up and because the compiler will
87// call it from any splittable prologue (leading to infinite
88// recursion).
89//
90// Ideally it should also use very little stack because the linker
91// doesn't currently account for this in nosplit stack depth checking.
92//
93// Ensure mayMoreStackPreempt can be called for all ABIs.
94//
95//go:nosplit
96//go:linkname mayMoreStackPreempt
97func mayMoreStackPreempt() {
98	// Don't do anything on the g0 or gsignal stack.
99	gp := getg()
100	if gp == gp.m.g0 || gp == gp.m.gsignal {
101		return
102	}
103	// Force a preemption, unless the stack is already poisoned.
104	if gp.stackguard0 < stackPoisonMin {
105		gp.stackguard0 = stackPreempt
106	}
107}
108
109// mayMoreStackMove is a maymorestack hook that forces stack movement
110// at every possible point.
111//
112// See mayMoreStackPreempt.
113//
114//go:nosplit
115//go:linkname mayMoreStackMove
116func mayMoreStackMove() {
117	// Don't do anything on the g0 or gsignal stack.
118	gp := getg()
119	if gp == gp.m.g0 || gp == gp.m.gsignal {
120		return
121	}
122	// Force stack movement, unless the stack is already poisoned.
123	if gp.stackguard0 < stackPoisonMin {
124		gp.stackguard0 = stackForceMove
125	}
126}
127
128// debugPinnerKeepUnpin is used to make runtime.(*Pinner).Unpin reachable.
129var debugPinnerKeepUnpin bool = false
130
131// debugPinnerV1 returns a new Pinner that pins itself. This function can be
132// used by debuggers to easily obtain a Pinner that will not be garbage
133// collected (or moved in memory) even if no references to it exist in the
134// target program. This pinner in turn can be used to extend this property
135// to other objects, which debuggers can use to simplify the evaluation of
136// expressions involving multiple call injections.
137func debugPinnerV1() *Pinner {
138	p := new(Pinner)
139	p.Pin(unsafe.Pointer(p))
140	if debugPinnerKeepUnpin {
141		// Make Unpin reachable.
142		p.Unpin()
143	}
144	return p
145}
146