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Stolb23 [73]
3 years ago
9

In the original UNIX operating system, a process executing in kernel mode may not be preempted. Explain why this makes (unmodifi

ed) UNIX unsuitable for real-time applications.
Computers and Technology
1 answer:
Elena L [17]3 years ago
5 0

Answer:

the preemption is -> The ability of the operating

system to preempt or stop a currently

scheduled task in favour of a higher priority

task. The scheduling may be one of, but not

limited to, process or 1/0 scheduling etc.

Under Linux, user-space programs have always

been preemptible: the kernel interrupts user

space programs to switch to other threads,

using the regular clock tick. So, the kernel

doesn't wait for user-space programs to

explicitly release the processor (which is the

case in cooperative multitasking). This means

that an infinite loop in an user-space program

cannot block the system.

However, until 2.6 kernels, the kernel itself was

not preemtible: as soon as one thread has

entered the kernel, it could not be preempted to

execute an other thread. However, this absence

of preemption in the kernel caused several

oroblems with regard to latency and scalability.

So, kernel preemption has been introduced in

2.6 kernels, and one can enable or disable it

using the cONFIG_PREEMPT option. If

CONFIG PREEMPT is enabled, then kernel code

can be preempted everywhere, except when the

code has disabled local interrupts. An infinite

loop in the code can no longer block the entire

system. If CONFIG PREEMPT is disabled, then

the 2.4 behaviour is restored.

So it suitable for real time application. Only

difference is we don't see many coders using it

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Describe the basic features of the relational data model and discuss their importance to the end user and the designer. Describe
Mandarinka [93]

Answer:

The answer to this question can be described as follows:

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6 0
3 years ago
There are two main types of hard drive available to a computer. State what they are and describe their use.
Gala2k [10]

Answer:

Hard disk drives (HDD), which use one or more rotating discs and rely on magnetic storage, and solid-state drives (SSD), which have no moving mechanical parts, but use flash memory like the kind found in USB flash drives.

Explanation:

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2 years ago
Given an array a, declared to contain 34 elements, write an expression that refers to the last element of the array.
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If the language is zero indexed:

a[ 33 ]
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What's good computing?
cestrela7 [59]

Answer:

1.Use passwords that can't be easily guessed, and protect your passwords.

2.Minimize storage of sensitive information.

3.Beware of scams.

4.Protect information when using the Internet and email.

5.Make sure your computer is protected with anti-virus and all necessary 6.security "patches" and updates.

7.Secure laptop computers and mobile devices at all times: Lock them up or carry them with you.

8.Shut down, lock, log off, or put your computer and other devices to sleep before leaving them unattended, and make sure they require a secure password to start up or wake-up.

9.Don't install or download unknown or unsolicited programs/apps.

Secure your area before leaving it unattended.

10.Make backup copies of files or data you are not willing to lose.

Explanation:

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