Home > Articles > Programming > Windows Programming

  • Print
  • + Share This
This chapter is from the book

Exercises

6-1.

Extend Program 6-1 (grepMP) so that it accepts command line options and not just the pattern.

6-2.

Rather than pass the temporary file name to the child process in Program 6-1, convert the inheritable file handle to a DWORD (a HANDLE requires 4 bytes in Win32; investigate the Win64 HANDLE size) and then to a character string. Pass this string to the child process on the command line. The child process, in turn, must convert the character string back to a handle value to use for output. The catHA.c and grepHA.c programs in the Examples file illustrate this technique. Is this technique advisable, or is it poor practice, in your opinion?

6-3.

Program 6-1 waits for all processes to complete before listing the results. It is impossible to determine the order in which the processes actually complete within the current program. Modify the program so that it can also determine the termination order. Hint: Modify the call to WaitForMultipleObjects so that it returns after each individual process terminates. An alternative would be to sort by the process termination times.

6-4.

The temporary files in Program 6-1 must be deleted explicitly. Can you use FILE_FLAG_DELETE_ON_CLOSE when creating the temporary files so that deletion is not required?

6-5.

Determine any grepMP performance advantages (compared with sequential execution) on different multiprocessor systems or when the files are on separate or network drives. Appendix C presents some partial results, as does Run 6-1.

6-6.

Can you find a way to collect the user and kernel time required by grepMP? It may be necessary to modify grepMP to use job objects.

6-7.

Enhance the DisplayJobs function (Program 6-5) so that it reports the exit code of any completed job. Also, give the times (elapsed, kernel, and user) used so far by all jobs.

6-8.

The job management functions have a defect that is difficult to fix. Suppose that a job is killed and the executive reuses its process ID before the process ID is removed from the job management file. There could be an OpenProcess on the process ID that now refers to a totally different process. The fix requires creating a helper process that holds duplicated handles for every created process so that the ID will not be reused. Another technique would be to include the process start time in the job management file. This time should be the same as the process start time of the process obtained from the process ID. Note: Process IDs will be reused quickly. UNIX, however, increments a counter to get a new process ID, and IDs will repeat only after the 32-bit counter wraps around. Therefore, Windows programs cannot assume that IDs will not, for all practical purposes, be reused.

6-9.

Modify JobShell so that job information is maintained in the registry rather than in a temporary file.

6-10.

Enhance JobShell so that the jobs command will include a count of the number of handles that each job is using. Hint: Use GetProcessHandleCount (see MSDN).

6-11.

Jobbg (in the JobShell listing) currently terminates a process if there is no room in the table for a new entry. Enhance the program to reserve a table location before creating the process, so as to avoid TerminateProcess.

6-12.

JobObjectShell exhibits several anomalies and defects. Investigate and fix or explain them, if possible.

  • Run 6-7 shows seven total processes, all active, after the first two jobs are started. This value is correct (do you agree?). After the jobs terminate, there are now 10 processes, none of which are active. Is this a bug (if so, is the bug in the program or in Windows?), or is the number correct?
  • Program 6-7 shows plausible user time results in seconds (do you agree?). It obtains these results by dividing the total user time by 1,000,000, implying that the time is returned in microseconds. MSDN, however, says that the time is in 100 ns units, so the division should be by 10,000,000. Investigate. Is MSDN wrong?
  • Does the limit on process time actually work, and is the program implemented correctly? sortBT (Program 5-1) is a time-consuming program for experimentation.
  • + Share This
  • 🔖 Save To Your Account