Reference no: EM1334170
When a child process is fork()ed, a parent may wait for the successful completion of the child via the wait() service (or one of its variants) so that the return result of that application can be read from the process descriptor block.
If the parent does not perform a wait() operation on the child process after it terminates, Unix will keep the process descriptor block active for this application in hopes that eventually the parent will wait() or that the parent will itself terminate.
If you perform the ps command in this scenario, you may find a number of "zombie" processes - these are processes marked with a Z in the output of ps that are children of a currently running parent that hasn't yet waited upon their completion. Normally, this isn't much of a problem, as eventually, the parent will terminate and cause the zombie tasks to be deallocated.
However, in a server application such as the email database server above, this becomes a problem, as the server generally never terminates, and as a result, the system list of process descriptor blocks becomes cluttered by zombies (processes that have properly terminated by haven't been waited upon by the parent).
To avoid this problem, Unix ensures that a terminating child application can send a signal to the parent indicating that it has terminated (SIG_CHILD). The parent should catch this signal, and issue a wait() or one of its variants to clean up the zombied process descriptor block.
For this question, describe the concept of a signal, and indicate how the parent application can be configured to act upon the SIG_CHILD signal from each child as they terminate to avoid the zombie issue.
In your answer, discuss the OS services that Unix provides to support signal processing.
|
Explaining future values and present values
: Find out the future value of $9,000 at the end of five periods at 8% compounded interest? Find out the present value of $9,000 due eight periods hence, discounted at 11%?
|
|
Taking decision regarding replacing looms
: SMM has decided to replace one of its looms and has researched the following cost data on replacement looms.
|
|
Explain the pros and cons of this marketing idea
: Explain the pros and cons of this marketing idea proposed by the company from the both a financial and non-financial perspective.
|
|
Pros and cons of using technology
: What do you see as being the pros and cons of using technology? Is it possible to rely too much on technology?
|
|
Terminate and cause the zombie tasks to be deallocated
: while a child process is fork()ed, a parent may wait for the successful completion of the child via the wait() service (or one of its variants) so that the return result of that application can be read from the process descriptor block.
|
|
Treasury bond interest rates
: Assume you own the 8% October 2008 treasury bond and it is expected that the market interest rate will increase from 8% to 9% in the next three months.
|
|
The processor save in fraction of its visits to keyboard
: In an 8-hour interval, an operator controls systems with 60 commands on an average, entered through a keyboard.
|
|
Controlling the metadata
: Does the Word version you are using provide any control over metadata, can you eliminate it, hide it, reduce it etc?
|
|
Determining subprime mortgage crisis
: What are the risks which are associated with debt, and why may those risks be unacceptable to the corporation that needs money?
|