How to Use CreateJobObject and SetInformationJobObject with PInvoke in .NET to Manage Process Termination?

Working Example of CreateJobObject/SetInformationJobObject PInvoke in .NET

Question:

I've been struggling to create a working example of using the CreateJobObject and SetInformationJobObject methods through PInvoke. Despite various attempts, I'm encountering errors when trying to set the JOBOBJECT_BASIC_LIMIT_INFORMATION using the SetInformationJobObject method.

Answer:

To address your issue, let's delve into the intricacies of working with CreateJobObject and SetInformationJobObject in .NET through PInvoke. Here's a step-by-step guide with a functional example:

1. Create a Job Object:

First, we'll create a job object using the CreateJobObject method. This method takes two arguments: a security attribute and the job name (which we'll leave empty).

IntPtr jobHandle = CreateJobObject( null , null );

2. Add Processes to the Job Object:

Next, we need to assign processes to our newly created job object. The AssignProcessToJobObject method is used for this purpose.

AssignProcessToJobObject( jobHandle , myProcess.Handle );
AssignProcessToJobObject( jobHandle , Process.GetCurrentProcess().Handle );

3. Set Job Limits:

Now, we'll set job limits using the SetInformationJobObject method. We'll specifically focus on setting the JOBOBJECT_LIMIT_KILL_ON_JOB_CLOSE flag.

JOBOBJECT_BASIC_LIMIT_INFORMATION limits = new JOBOBJECT_BASIC_LIMIT_INFORMATION();
limits.LimitFlags = (short)LimitFlags.JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE;
IntPtr pointerToJobLimitInfo = Marshal.AllocHGlobal( Marshal.SizeOf( limits ) );
Marshal.StructureToPtr( limits , pointerToJobLimitInfo , false );   
SetInformationJobObject( job , JOBOBJECTINFOCLASS.JobObjectBasicLimitInformation , pionterToJobLimitInfo ,  ( uint )Marshal.SizeOf( limits ) )

In this code, we've defined the JOBOBJECT_BASIC_LIMIT_INFORMATION structure and set the LimitFlags to JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE. This ensures that when one process in the job object is terminated, the other processes are also automatically terminated.

Complete Code Example:

Here's the complete code example that incorporates these steps:

using System;
using System.Diagnostics;
using System.Runtime.InteropServices;

class Program
{
    [DllImport( "kernel32.dll" , EntryPoint = "CreateJobObjectW" , CharSet = CharSet.Unicode )]
    public static extern IntPtr CreateJobObject( IntPtr JobAttributes , string lpName );

    [DllImport( "kernel32.dll" )]
    static extern bool SetInformationJobObject( IntPtr hJob , JOBOBJECTINFOCLASS JobObjectInfoClass , IntPtr lpJobObjectInfo , uint cbJobObjectInfoLength );

    public enum JOBOBJECTINFOCLASS
    {
        JobObjectAssociateCompletionPortInformation = 7 ,
        JobObjectBasicLimitInformation = 2 ,
        JobObjectBasicUIRestrictions = 4 ,
        JobObjectEndOfJobTimeInformation = 6 ,
        JobObjectExtendedLimitInformation = 9 ,
        JobObjectSecurityLimitInformation = 5
    }


    [StructLayout( LayoutKind.Sequential )]
    struct JOBOBJECT_BASIC_LIMIT_INFORMATION
    {
        public Int64 PerProcessUserTimeLimit;
        public Int64 PerJobUserTimeLimit;
        public Int16 LimitFlags;
        public UIntPtr MinimumWorkingSetSize;
        public UIntPtr MaximumWorkingSetSize;
        public Int16 ActiveProcessLimit;
        public Int64 Affinity;
        public Int16 PriorityClass;
        public Int16 SchedulingClass;
    }

    public enum LimitFlags
    {
        JOB_OBJECT_LIMIT_ACTIVE_PROCESS = 0x00000008 ,
        JOB_OBJECT_LIMIT_AFFINITY = 0x00000010 ,
        JOB_OBJECT_LIMIT_BREAKAWAY_OK = 0x00000800 ,
        JOB_OBJECT_LIMIT_DIE_ON_UNHANDLED_EXCEPTION = 0x00000400 ,
        JOB_OBJECT_LIMIT_JOB_MEMORY = 0x00000200 ,
        JOB_OBJECT_LIMIT_JOB_TIME = 0x00000004 ,
        JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE = 0x00002000 ,
        JOB_OBJECT_LIMIT_PRESERVE_JOB_TIME = 0x00000040 ,
        JOB_OBJECT_LIMIT_PRIORITY_CLASS = 0x00000020 ,
        JOB_OBJECT_LIMIT_PROCESS_MEMORY = 0x00000100 ,
        JOB_OBJECT_LIMIT_PROCESS_TIME = 0x00000002 ,
        JOB_OBJECT_LIMIT_SCHEDULING_CLASS = 0x00000080 ,
        JOB_OBJECT_LIMIT_SILENT_BREAKAWAY_OK = 0x00001000 ,
        JOB_OBJECT_LIMIT_WORKINGSET = 0x00000001
    }


    [DllImport( "kernel32.dll" )]
    [return: MarshalAs( UnmanagedType.Bool )]
    static extern bool AssignProcessToJobObject( IntPtr hJob , IntPtr hProcess );

    static void Main( string[] args )
    {
        Process myProcess = // POPULATED SOMEWHERE ELSE

        // Create Job & assign this process and another process to the job
        IntPtr jobHandle = CreateJobObject( null , null );
        AssignProcessToJobObject( jobHandle , myProcess.Handle );
        AssignProcessToJobObject( jobHandle , Process.GetCurrentProcess().Handle );

        // Ensure that killing one process kills the others                
        JOBOBJECT_BASIC_LIMIT_INFORMATION limits = new JOBOBJECT_BASIC_LIMIT_INFORMATION();
        limits.LimitFlags = (short)LimitFlags.JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE;
        IntPtr pointerToJobLimitInfo = Marshal.AllocHGlobal( Marshal.SizeOf( limits ) );
        Marshal.StructureToPtr( limits , pointerToJobLimitInfo , false );   
        SetInformationJobObject( job , JOBOBJECTINFOCLASS.JobObjectBasicLimitInformation , pionterToJobLimitInfo ,  ( uint )Marshal.SizeOf( limits ) )
    }
}

This code will create a job object, add the current process and another process (specified by myProcess) to the job object, and set the JOBOBJECT_LIMIT_KILL_ON_JOB_CLOSE flag. By doing so, when either the current process or the myProcess is terminated, the other process will also be terminated automatically.

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