Real-Time Signal Handling In Guest And Host Operating Systems

• US 20100138685A1
• Filed: 11/25/2009
• Published: 06/03/2010
• Est. Priority Date: 11/28/2008
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Kass, Eric
• Granted Patent: US 8,060,788 B2
• Time in Patent Office: Days
• US Class Current: 714/2
• CPC Class Codes: G06F 9/4812 by interrupt, e.g. masked
• CPC Class Codes: G06F 9/526 Mutual exclusion algorithms

Abstract

The present invention relates to signal handling in a host operating system process executing code portions of a single- or multi-threaded application and of the embedded guest operating system. When a signal is sent from the host operating system to the operating system process, the signal handler of the guest operating system will be invoked in a deterministic time, independent of the operating system process executing code portions of the application or of the guest operating system or executing system calls of the host operating system in a masked or non-masked operation.

Claims

1. A method comprising,

providing an operating system process, the operating system process executing application code portions, system calls of a host operating system, and system calls of a guest operating system, the guest operating system being embedded in the host operating system, the operating system process comprising a worker thread dedicated to executing the application code portions such that when started the worker thread creates an associated signal-waiter thread dedicated to handling specific signals from the host operating system and the worker thread being masked to signals from the host operating system to the operating system process to prevent interruption of the flow of execution of the worker thread;

and,

catching a specific signal of the signal-waiter thread from the host operating system, the catching further comprising

in response to the specific caught signal while the worker thread is executing a system call of the host operating system, the signal-waiter thread protecting the worker thread from executing application code portions and system calls of the guest operating system,

the signal-waiter thread executing code portions for handling signals from the guest operating system adapted to the specific signal from the host operating system, and,

the signal-waiter thread allowing the worker thread to execute application code portions and system calls of the guest operating system after the signal-waiter thread has finished handling the specific signal.

2. The method according to claim 1, wherein the worker thread performs error handling when the signal-waiter thread ended abnormally and does not allow the worker thread to execute application code portions and system calls of the guest operating system.

3. The method according to claim 2, wherein the error handling performed by the worker thread comprises terminating the operating system process.

4. The method according to claim 1, wherein the worker thread is also masked to signals from the guest operating system.

5. The method according to claim 1, wherein

the signal-waiter thread is protecting the worker thread from executing application code portions and system calls of the guest operating system by acquiring a mutex lock,

the signal-waiter thread is allowing the worker thread to execute application code portions and system calls of the guest operating system by releasing the mutex lock,

the error handling performed by the worker thread is triggered when the worker thread fails to acquire the mutex lock because the signal-waiter thread has ended abnormally while owning the mutex lock.

6. The method according to claim 1, further comprising:

in response to the specific caught signal and while the worker thread is not executing a system call of the host operating system and the worker thread is not masked to signals from the guest operating system,

the signal-waiter thread invoking the worker thread to execute code portions for handling signals from the guest operating system adapted to the specific signal.

7. The method according to claim 1, wherein a second operating system process is executing a system call of the guest operating system to send a signal to the first operating system process, and then the guest operating system is executing a system call of the host operating system to send the specific signal, which is adapted to the signal from the second operating system process, to first the operating system process.

8. The method according to claim 1, wherein the system call of the host operating system is performing a database operation.

9. A system comprising,

a processor;

a data bus coupled to the processor; and

,

a computer usable medium embodying computer program code, the computer usable medium being coupled to the data bus, the computer program code comprising instructions executable by the processor and configured for;

providing an operating system process, the operating system process executing application code portions, system calls of a host operating system, and system calls of a guest operating system, the guest operating system being embedded in the host operating system, the operating system process comprising a worker thread dedicated to executing the application code portions such that when started the worker thread creates an associated signal-waiter thread dedicated to handling specific signals from the host operating system and the worker thread being masked to signals from the host operating system to the operating system process to prevent interruption of the flow of execution of the worker thread; and

,

catching a specific signal of the signal-waiter thread from the host operating system, the catching further comprising

in response to the specific caught signal while the worker thread is executing a system call of the host operating system, the signal-waiter thread protecting the worker thread from executing application code portions and system calls of the guest operating system,

the signal-waiter thread executing code portions for handling signals from the guest operating system adapted to the specific signal from the host operating system, and,

the signal-waiter thread allowing the worker thread to execute application code portions and system calls of the guest operating system after the signal-waiter thread has finished handling the specific signal.

10. The system according to claim 9, wherein the worker thread performs error handling when the signal-waiter thread ended abnormally and does not allow the worker thread to execute application code portions and system calls of the guest operating system.

11. The system according to claim 10, wherein the error handling performed by the worker thread comprises terminating the operating system process.

12. The system according to claim 9, wherein the worker thread is also masked to signals from the guest operating system.

13. The system according to claim 9, wherein

the signal-waiter thread is protecting the worker thread from executing application code portions and system calls of the guest operating system by acquiring a mutex lock,

the signal-waiter thread is allowing the worker thread to execute application code portions and system calls of the guest operating system by releasing the mutex lock,

the error handling performed by the worker thread is triggered when the worker thread fails to acquire the mutex lock because the signal-waiter thread has ended abnormally while owning the mutex lock.

14. The system according to claim 9, further comprising:

in response to the specific caught signal and while the worker thread is not executing a system call of the host operating system and the worker thread is not masked to signals from the guest operating system,

the signal-waiter thread invoking the worker thread to execute code portions for handling signals from the guest operating system adapted to the specific signal.

15. The system according to claim 9, wherein a second operating system process is executing a system call of the guest operating system to send a signal to the first operating system process, and then the guest operating system is executing a system call of the host operating system to send the specific signal, which is adapted to the signal from the second operating system process, to first the operating system process.

16. The system according to claim 9, wherein the system call of the host operating system is performing a database operation.