GATE IT 2005 | Question: 19, UGCNET-June2012-III: 57

Question

A user level process in Unix traps the signal sent on a Ctrl-C input, and has a signal handling routine that saves appropriate files before terminating the process. When a Ctrl-C input is given to this process, what is the mode in which the signal handling routine executes?

• A. User mode
• B. Kernel mode
• C. Superuser mode
• D. Privileged mode

Comments

signals may be handled by two possible handlers,default or if user defined overriding default one.Here which is handling the signal?default or user defined?

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I think this question could be done by option elimination method:

Since b and d are the same hence they both cannot be the answer as multiple options not allowed.

Now, superuser mode is a mode that requires an administrator to do certain tasks.

Now think of a situation when you are using a computer in guest mode. Now you have written an infinite loop program and running in cmd. Now to stop cmd you will press ctrl+c and immediately the program stops without asking any permission. Now, this means CPU does not ask you for admin permission to do ctrl+c. This means the task can be done without going superuser mode.

Now, you have only one option left. Hence, A will be the answer.

Please correct if I'm wrong.

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is this in syllabus?

Answer 1

• When an user send an input to the process it can not be in privileged mode  as it is coming from an user so option D , Privileged mode can not be possible here ..

Now see , kernel mode = Privileged mode 

• That means both option B and option D are equal. As option D can not be possible , option B also false.
• There is nothing called  superuser mode so option C is clearly wrong .
• Only option A is left , when an user input come like ' ctrl+c' the signal handling routine executes in user mode only as a user level process in UNIX traps the signal.

Hence option A is correct answer.

Comments

@Krithiga2101

 https://gateoverflow.in/3764/gate2005-it-19-ugcnet-june2012-iii-57?show=148151#c148151

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superuser mode ---

Sudo command

Sudo (superuser do) is a utility for UNIX- and Linux-based systems that provides an efficient way to give specific users permission to use specific system commands at the root (most powerful) level of the system

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@BikramIn Linux we write sudo...something. Which means user mode, right?

Answer 2

 

This is what the Galvin text has to say.  Usually, there are two types of signal handlers: Kernel Level and user level. Now the kernel level is the default one. But if we look at the wordings of the question in details :

A user level process in Unix traps the signal sent on a Ctrl-C input, and has a signal handling routine that saves appropriate files before terminating the process.

It clearly means that the signal handling routine is a part of the user-level process and hence it shall run in user mode.

 

Ans: (A) USER MODE

 

Comments

This shd be the best ans.

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We should mark it as best answer

Answer 3

http://computernetsolved.blogspot.in/2015/05/q57paper-3-j-12-user-level-process-in.html

Comments

according to this link it should be kernel mode right?

Answer 4

Answer: A

Comments

what is the difference between kernel mode and privledge mode... ?? why only A is answer not C?

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Privilege mode and kernel mode both are the same thing so the  answer can be A or C

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@S Ram

Kernel mode == Privileged mode

so option B == option D , when an user send a request it can not be in privileged mode so both option B and D are wrong ..

there is nothing called super user mode so option C is wrong clearly ..

we only left with option A , and that is correct option .

Answer 5

Answer = Kernel mode.
Explanation.
Hardware interrupts (also called external/asynchronous interrupts), are ones in which the notification originates from a hardware device such as a keyboard, mouse , etc.
The most common way of sending signals to processes is using the keyboard:
• Ctrl-C: Causes the system to send an INT signal (SIGINT) to the running process.
• Ctrl-Z: causes the system to send a TSTP signal (SIGTSTP) to the running process.
The kernel handles signals in the context of the process that receives them, so
a process must run to handle signals.

Answer 6

The question says "signal handling routine that saves appropriate files BEFORE TERMINATING THE PROCESS" . This means we are still in user mode. So answer is A.