Avoid sending a signal to the container during checkpointing #11054
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When checkpointing, the container.SignalContainer will be blocked until the end of the checkpointing process, during which it cannot acquire the kernel.extMu mutex. As a result, some runsc commands, such as the runsc list, will have to wait. The waiting time may vary with the duration of the checkpoint. This patch adds a flag to prevent sending signals to the container during checkpointing. Signed-off-by: Dawei Shen <[email protected]>
avagin
reviewed
Oct 19, 2024
| @@ -452,6 +456,9 @@ func (cm *containerManager) ExecuteAsync(args *control.ExecArgs, pid *int32) err | |||
| // Checkpoint pauses a sandbox and saves its state. | |||
| func (cm *containerManager) Checkpoint(o *control.SaveOpts, _ *struct{}) error { | |||
| log.Debugf("containerManager.Checkpoint") | |||
| cm.inCheckpointing.CompareAndSwap(0, -1) | |||
| defer cm.inCheckpointing.CompareAndSwap(-1, 0) | |||
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This doesn't look right. Why do we use CompareAndSwap here? Can more than one checkpoint operation run concurrently? If the answer is yest, so we probably need to use cm.inCheckpointing.Add(1); defer cm.inCheckpointing.Add(-1).
avagin
reviewed
Oct 19, 2024
| @@ -788,6 +795,9 @@ type SignalArgs struct { | |||
| // process group. | |||
| func (cm *containerManager) Signal(args *SignalArgs, _ *struct{}) error { | |||
| log.Debugf("containerManager.Signal: cid: %s, PID: %d, signal: %d, mode: %v", args.CID, args.PID, args.Signo, args.Mode) | |||
| if cm.inCheckpointing.Load() != 0 { | |||
| return nil | |||
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This doesn't look right either. We can't return success if the signal hasn't been sent....
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When checkpointing, the container.SignalContainer will be blocked until the end of the checkpointing process, during which it cannot acquire the kernel.extMu mutex. As a result, some runsc commands, such as the runsc list, will have to wait. The waiting time may vary with the duration of the checkpoint. This patch adds a flag to prevent sending signals to the container during checkpointing.