High CPU usage when backgrounding CLI with -i

Bắt đầu bằng cách tái hiện trường hợp docker run -i --rm alpine:latest sleep 300000 & chạy ở chế độ nền và kiểm tra cli/streams/in.go cùng cli/command/container/hijack.go, đặc biệt là hijackedIOStreamer.beginInputStream. Sử dụng các quan sát strace và GDB được cung cấp để theo dõi hành vi của luồng đầu vào. Công việc được xem là hoàn tất khi CLI chạy ở chế độ nền không còn tiêu thụ CPU quá mức mà vẫn duy trì hành vi mong đợi của container.

Description

When running a docker container with the -i option combined with backgrounding the process (e.g. using & at the end of the bash command), CPU usage jumps to 100% for the docker CLI process

Reproduce

1. Open bash, or any other shell that supports & backgrounding
2. docker run -i --rm alpine:latest sleep 300000 &

Expected behavior

The process should continue to run in the background, but just not accept input unless foregrounded.

docker version

Client: Docker Engine - Community
 Version:           28.0.4
 API version:       1.48
 Go version:        go1.23.7
 Git commit:        b8034c0
 Built:             Tue Mar 25 15:07:16 2025
 OS/Arch:           linux/amd64
 Context:           default

Server: Docker Engine - Community
 Engine:
  Version:          28.0.4
  API version:      1.48 (minimum version 1.24)
  Go version:       go1.23.7
  Git commit:       6430e49
  Built:            Tue Mar 25 15:07:16 2025
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.7.27
  GitCommit:        05044ec0a9a75232cad458027ca83437aae3f4da
 runc:
  Version:          1.2.5
  GitCommit:        v1.2.5-0-g59923ef
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0

docker info

Client: Docker Engine - Community
 Version:    28.0.4
 Context:    default
 Debug Mode: false
 Plugins:
  buildx: Docker Buildx (Docker Inc.)
    Version:  v0.22.0
    Path:     /usr/libexec/docker/cli-plugins/docker-buildx
  compose: Docker Compose (Docker Inc.)
    Version:  v2.34.0
    Path:     /usr/libexec/docker/cli-plugins/docker-compose

Server:
 Containers: 3
  Running: 3
  Paused: 0
  Stopped: 0
 Images: 3
 Server Version: 28.0.4
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Using metacopy: false
  Native Overlay Diff: true
  userxattr: false
 Logging Driver: json-file
 Cgroup Driver: cgroupfs
 Cgroup Version: 1
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local splunk syslog
 Swarm: inactive
 Runtimes: io.containerd.runc.v2 runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 05044ec0a9a75232cad458027ca83437aae3f4da
 runc version: v1.2.5-0-g59923ef
 init version: de40ad0
 Security Options:
  seccomp
   Profile: builtin
 Kernel Version: 5.15.167.4-microsoft-standard-WSL2
 Operating System: Ubuntu 24.04.2 LTS
 OSType: linux
 Architecture: x86_64
 CPUs: 16
 Total Memory: 15.47GiB
 Name: jwilco7670l
 ID: 74516f92-1428-475d-b1e6-b8d039ba0a8b
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 Experimental: false
 Insecure Registries:
  docker.adtran.com:5000
  cn-docker.adtran.com:5000
  ::1/128
  127.0.0.0/8
 Live Restore Enabled: false
 Default Address Pools:
   Base: 10.120.128.0/17, Size: 24

WARNING: No blkio throttle.read_bps_device support
WARNING: No blkio throttle.write_bps_device support
WARNING: No blkio throttle.read_iops_device support
WARNING: No blkio throttle.write_iops_device support

Additional Info

I did some light attempts at diagnosing what is going on.

With an strace capture, I see tons of these events:

read(0, 0xc00027c000, 32768)            = ? ERESTARTSYS (To be restarted if SA_RESTART is set)
read(0, 0xc00027c000, 32768)            = ? ERESTARTSYS (To be restarted if SA_RESTART is set)
read(0, 0xc00027c000, 32768)            = ? ERESTARTSYS (To be restarted if SA_RESTART is set)
read(0, 0xc00027c000, 32768)            = ? ERESTARTSYS (To be restarted if SA_RESTART is set)
read(0, 0xc00027c000, 32768)            = ? ERESTARTSYS (To be restarted if SA_RESTART is set)

If I attach to the process with GDB, the process is seems to live in this call stack pretty consistently:

(gdb) thread apply all bt

Thread 1 (Thread 0x7f899e7fc6c0 (LWP 27495) "docker"):
#0  runtime.futex () at /usr/local/go/src/runtime/sys_linux_amd64.s:558
#1  0x0000558e960fc470 in runtime.futexwakeup (addr=0x1, cnt=1) at /usr/local/go/src/runtime/os_linux.go:82
#2  0x0000558e960d5625 in runtime.notewakeup (n=0x1) at /usr/local/go/src/runtime/lock_futex.go:155
#3  0x0000558e9611963c in runtime.sigsend (s=<optimized out>, ~r0=<optimized out>) at /usr/local/go/src/runtime/sigqueue.go:116
#4  0x0000558e96118048 in runtime.sighandler (sig=21, info=<optimized out>, ctxt=<optimized out>, gp=0xc0004c6380) at /usr/local/go/src/runtime/signal_unix.go:722
#5  0x0000558e9611796a in runtime.sigtrampgo (sig=21, info=0xc00050dbf0, ctx=0xc00050dac0) at /usr/local/go/src/runtime/signal_unix.go:490
#6  0x0000558e96141a29 in runtime.sigtramp () at /usr/local/go/src/runtime/sys_linux_amd64.s:352
#7  <signal handler called>
#8  internal/runtime/syscall.Syscall6 () at /usr/local/go/src/internal/runtime/syscall/asm_linux_amd64.s:35
#9  0x0000558e9619a50d in syscall.RawSyscall6 (trap=0, a1=0, a2=94070891631086, a3=0, a4=824636325888, a5=0, a6=0, r1=<optimized out>, r2=<optimized out>, err=<optimized out>) at /usr/local/go/src/syscall/syscall_linux.go:64
#10 0x0000558e9619a566 in syscall.Syscall (trap=0, a1=0, a2=824636325888, a3=32768, r1=<optimized out>, r2=<optimized out>, err=<optimized out>) at /usr/local/go/src/syscall/syscall_linux.go:86
#11 0x0000558e96198558 in syscall.read (fd=<optimized out>, p=..., n=<optimized out>, err=...) at /usr/local/go/src/syscall/zsyscall_linux_amd64.go:736
#12 0x0000558e961baf6e in syscall.Read (fd=0, p=..., n=<optimized out>, err=...) at /usr/local/go/src/syscall/syscall_unix.go:183
#13 internal/poll.ignoringEINTRIO (fd=0, p=..., fn=<optimized out>) at /usr/local/go/src/internal/poll/fd_unix.go:745
#14 internal/poll.(*FD).Read (fd=0xc00014a000, p=..., ~r0=<optimized out>, ~r0=<optimized out>, ~r1=..., ~r1=...) at /usr/local/go/src/internal/poll/fd_unix.go:161
#15 0x0000558e961c67b2 in os.(*File).read (f=0xc000134098, b=..., n=<optimized out>, err=...) at /usr/local/go/src/os/file_posix.go:29
#16 os.(*File).Read (f=0xc000134098, b=..., n=<optimized out>, err=...) at /usr/local/go/src/os/file.go:124
#17 0x0000558e965d3a22 in github.com/docker/cli/cli/streams.(*In).Read (i=<optimized out>, p=..., ~r0=<optimized out>, ~r1=...) at /go/src/github.com/docker/cli/cli/streams/in.go:21
#18 0x0000558e96189531 in io.copyBuffer (dst=..., src=..., buf=..., written=<optimized out>, err=...) at /usr/local/go/src/io/io.go:429
#19 0x0000558e969b7572 in io.Copy (dst=..., src=..., err=..., written=<optimized out>) at /usr/local/go/src/io/io.go:388
#20 github.com/docker/cli/cli/command/container.(*hijackedIOStreamer).beginInputStream.func1 () at /go/src/github.com/docker/cli/cli/command/container/hijack.go:150
#21 0x0000558e9613ff01 in runtime.goexit () at /usr/local/go/src/runtime/asm_amd64.s:1700
#22 0x0000000000000000 in ?? ()

Additionally in GDB when I resume the process I can see it is receiving a lot of these signals:

(gdb) c
Continuing.

Program received signal SIGTTIN, Stopped (tty input).
internal/runtime/syscall.Syscall6 () at /usr/local/go/src/internal/runtime/syscall/asm_linux_amd64.s:36
warning: 36     /usr/local/go/src/internal/runtime/syscall/asm_linux_amd64.s: No such file or directory
(gdb)