gate.go RawHistoryFolder

1// SPDX-License-Identifier: MIT
2
3package sandbox
4
5import (
6	"context"
7	"errors"
8	"sync"
9)
10
11// BootGate lets Stop abort a Start in progress. Start holds the sandbox's own
12// mutex for the whole boot (up to the boot timeout), so Stop could otherwise
13// only wait for it; with a gate, Stop first calls Abort, which cancels the
14// context Start runs its boot with, and then takes the mutex.
15type BootGate struct {
16	mu      sync.Mutex
17	cancel  context.CancelFunc
18	aborted bool
19}
20
21// ErrAborted is the cause of a boot cancelled by Stop.
22var ErrAborted = errors.New("sandbox: start aborted by Stop")
23
24// Begin returns the context to boot with: parent, cancelled by Abort. It fails
25// when Abort was already called (Stop before Start).
26func (g *BootGate) Begin(parent context.Context) (context.Context, error) {
27	g.mu.Lock()
28	defer g.mu.Unlock()
29	if g.aborted {
30		return nil, ErrAborted
31	}
32	ctx, cancel := context.WithCancelCause(parent)
33	g.cancel = func() { cancel(ErrAborted) }
34	return ctx, nil
35}
36
37// End must be called when the boot finished, successfully or not.
38func (g *BootGate) End() {
39	g.mu.Lock()
40	defer g.mu.Unlock()
41	if g.cancel != nil {
42		g.cancel()
43		g.cancel = nil
44	}
45}
46
47// Abort cancels a boot in progress and forbids a later Begin. It never blocks.
48func (g *BootGate) Abort() {
49	g.mu.Lock()
50	defer g.mu.Unlock()
51	g.aborted = true
52	if g.cancel != nil {
53		g.cancel()
54	}
55}